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  • Gravity, Geodesy and Tides  (98)
  • bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy
  • Oxford University Press  (111)
  • Palgrave Macmillan  (12)
  • Cambridge University Press  (7)
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  • 1
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    Equality, Freedom, and Democracy (2021)
    Oxford University Press
    Details
    Publication Date: 2021-02-10
    Description: A democratic regime is assumed to implement freedom and equality as the two critical and most important values. The question we intend to address here is: how and why has the actual implementation of freedom and equality been changing in the 1990–2020 period? Researching this topic, we cannot ignore the impact of the Great Recession since 2008. Thus, in this comparative research, we analyse France, Germany, Italy, Poland, Spain, and the United Kingdom to detect the changes. As expected, the six largest European democracies have been differently affected by the crisis, as they also had different background factors. We address an additional question: what is the impact of the European Union on the two democratic values? Accordingly, we analyse economic inequality, social inequality, and ethnic inequality with the related changing trends and explanations. We also detect and analyse the trend of freedoms, and especially personal dignity, civil rights, and political rights. Thus, the relative decline of equalities and freedoms in the six countries emerge in the different complex facets. We also explore the demand for equalities and freedoms by citizens and the political commitments of party leaders. The other issues we address include how and why, respectively, equalities and freedoms are affected by domestic aspects and the role of external factors, especially the European Union. By connecting equalities and freedoms and drawing the lines of entire research, we show how there are three different paths in the future of democracy: balanced democracy, protest democracy, and unaccountable democracy.
    Keywords: democracy ; equality ; freedom ; great recession ; inter-institutional accountability ; rule of law ; responsiveness ; bic Book Industry Communication::J Society & social sciences::JP Politics & government::JPB Comparative politics ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy ; bic Book Industry Communication::1 Geographical Qualifiers::1Q Other geographical groupings, oceans & seas::1QF Political, socio-economic & strategic groupings::1QFE EU (European Union)
    Language: English
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  • 2
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    The Political Regulation Wave (2022)
    Cambridge University Press
    Details
    Publication Date: 2022-08-09
    Description: Why has there been uneven success in reducing air pollution even in the same locality over time? This book offers an innovative theorization of how local political incentives can systematically affect bureaucratic regulation and empirically examines the control of different air pollutants in China and – to a lesser extent – in Mexico.?
    Keywords: political theory ; environmental law and engineering ; China studies ; air pollution studies ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCN Environmental economics ; bic Book Industry Communication::J Society & social sciences::JP Politics & government::JPA Political science & theory
    Language: English
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  • 3
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    Cultural Integration of Immigrants in Europe (2021)
    Oxford University Press
    Details
    Publication Date: 2022-05-13
    Description: The concepts of cultural diversity and cultural identity are at the forefront of the political debate in many western societies. In Europe, the discussion is stimulated by the political pressures associated with immigration flows, which are increasing in many European countries. The imperatives that current immigration trends impose on European democracies bring to light a number of issues that need to be addressed. What are the patterns and dynamics of cultural integration? How do they differ across immigrants of different ethnic groups and religious faiths? How do they differ across host societies? What are the implications and consequences for market outcomes and public policy? Which kind of institutional contexts are more or less likely to accommodate the cultural integration of immigrants? All these questions are crucial for policy makers and await answers. This book aims to provide a stepping stone to the debate. Taking an economic perspective, this edited book presents a current, comparative picture of the process of cultural integration of immigrants across Europe. It documents the main economic debates on the causes and consequences of cultural integration of immigrants, and provides detailed descriptions of the cultural and economic integration process in seven main European countries, including France, Germany, Italy, Spain, Sweden, Switzerland, and the United Kingdom. It also compares the European context with the integration of immigrants in the United States.
    Keywords: immigration ; european models of integration ; economic integration ; integration of immigrants ; cultural integration ; Eastern Europe ; Ethnic group ; Germany ; Second-generation immigrants in the United States ; Switzerland ; bic Book Industry Communication::J Society & social sciences::JF Society & culture: general::JFF Social issues & processes::JFFN Migration, immigration & emigration ; bic Book Industry Communication::J Society & social sciences::JH Sociology & anthropology::JHB Sociology::JHBD Population & demography ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy
    Language: English
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  • 4
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    The Economisation of Climate Change (2022)
    Cambridge University Press
    Details
    Publication Date: 2022-08-09
    Description: International economic institutions economise climate change, treating it as an economic rather than environmental issue. This book explores how three such institutions - G20, IMF, OECD - have addressed climate finance and fossil fuel subsidies, and the consequences of the economisation of climate change. Also available as Open Access.
    Keywords: climate change ; environmental policy ; environmental economics ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCN Environmental economics ; bic Book Industry Communication::R Earth sciences, geography, environment, planning::RN The environment::RNP Pollution & threats to the environment::RNPG Climate change ; bic Book Industry Communication::K Economics, finance, business & management::KN Industry & industrial studies::KNB Energy industries & utilities::KNBP Petroleum & oil industries ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy
    Language: English
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  • 5
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    The Palgrave Handbook of International Energy Economics (2022)
    Springer Nature | Palgrave Macmillan
    Details
    Publication Date: 2022-06-21
    Description: This open access handbook is distinguished by its emphasis on international energy, rather than domestic energy policies or international geopolitic aspects. Addressing key topics such as energy production and distribution, renewables and corporate energy structures, alongside global energy trends, regional case studies and emerging areas such as the digitalization of energy and energy transition, this handbook provides a major new contribution to the field of international energy economics. Written by academics, practitioners and policy-makers, this handbook is a valuable and timely addition to the literature on international energy economics. This book was published open access with the support of Eni.
    Keywords: Economics of energy production and distribution ; oil ; gas ; coal ; electricity ; biofuels ; Economics of power generation ; Economics of renewables ; Energy transition ; Energy financing ; International trade in energy ; Corporate energy structures ; Digitalization in Energy ; Cyber-security in energy ; Energy demand for buildings/industry/transportation ; Decarbonization ; Energy subsidies ; Vertical integration in energy ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCN Environmental economics ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy ; bic Book Industry Communication::T Technology, engineering, agriculture::TH Energy technology & engineering
    Language: English
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  • 6
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    Social Sector in a Decentralized Economy (2022)
    Cambridge University Press
    Details
    Publication Date: 2022-08-09
    Description: This book is an analytical examination of financing and public service delivery challenges in a decentralized framework. In addition, it provides critical insights into the effectiveness of public expenditure, through benefit incidence analysis of education and healthcare services in India.
    Keywords: economics ; policy ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCM Development economics & emerging economies ; bic Book Industry Communication::J Society & social sciences::JP Politics & government::JPP Public administration ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy
    Language: English
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  • 7
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    Governing Failure (2021)
    Cambridge University Press
    Details
    Publication Date: 2023-06-06
    Description: Jacqueline Best argues that the changes in International Monetary Fund, World Bank and donor policies in the 1990s, towards what some have called the 'Post-Washington Consensus,' were driven by an erosion of expert authority and an increasing preoccupation with policy failure. Failures such as the Asian financial crisis and the decades of despair in sub-Saharan Africa led these institutions to develop governance strategies designed to avoid failure: fostering country ownership, developing global standards, managing risk and vulnerability and measuring results. In contrast to the structural adjustment era when policymakers were confident that they had all the answers, the author argues that we are now in an era of provisional governance, in which key actors are aware of the possibility of failure even as they seek to inoculate themselves against it. This book considers the implications of this shift, asking if it is a positive change and whether it is sustainable. This title was made Open Access by libraries from around the world through Knowledge Unlatched.
    Keywords: nongovernmental organisations ; economic assistance ; politics ; development banks ; economic development - finance ; corporate governance ; international devleopment policy ; Conditionality ; Good governance ; Structural adjustment ; World Bank ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy
    Language: English
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  • 8
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    Hunger and Public Action (2021)
    Oxford University Press
    Details
    Publication Date: 2021-02-10
    Description: This book analyses the role of public action in solving the problem of hunger in the modern world. The study is divided into four parts. The first, making extensive use of the concepts of entitlements and capabilities explores the interaction of nutritional, economic, social, and political elements and their influence on hunger and deprivation. The problem of famine prevention is the main focus of the second part, with special attention given to Africa and India. The third part is devoted to the issue of fighting chronic undernourishment and the lessons to be learnt from the policies of China, India, and some other countries. The last part draws together the main themes and concerns of the earlier chapters, and provides an integrated view of the role of public action in eliminating hunger. The study suggests that there is indeed some space for public action in solving the problem of hunger and deprivation. In the case of famine prevention, social security could provide early warning systems and employment provision plans. To fight endemic deprivation, the authors suggest, among other things, that basic health care, elementary education, and food programmes should be looked at.
    Keywords: capability ; chronic undernourishment ; deprivation ; entitlements ; famine ; hunger ; public action ; social security ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCM Development economics & emerging economies ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCR Welfare economics
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  • 9
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    Pockets of Effectiveness and the Politics of State-building and Development in Africa (2023)
    Oxford University Press
    Details
    Publication Date: 2023-08-17
    Description: Why do certain parts of the state in Africa work so effectively despite operating in difficult governance contexts? How do 'pockets of bureaucratic effectiveness' emerge and become sustained over time? And what does this tell us about the prospects for state-building and development in Africa? Repeated economic and social crises have demanded that development thinkers and policy actors have had to engage with the critical role that states play in delivering development. Pockets of Effectiveness and the Politics of State-building and Development in Africa shows that politics is the driving factor that shapes how well state agencies perform their roles. It deploys a new conceptual framework – the power domains approach – to explore the shifting fortunes of key state agencies in five countries – Ghana, Kenya, Rwanda, Uganda, and Zambia – over the past three decades. Our original research reveals when, how and why political rulers decide to build effective state agencies and enable them to deliver certain forms of economic development – often through forming strategic coalitions with senior bureaucrats and with international support – and also when this support falters and gives way to a politics of survival. Comparative analysis identifies two potential trajectories towards state-building in Africa, each shaped by different configurations of social and political power. The book critiques the role that international development agencies have played in (mis)shaping the state in Africa and suggests a new strategic agenda for building the state capacities required to deliver sustained development at the current juncture. The book closes with critical commentaries from two leading scholars in the field, to help place our work in context and establish the next steps for research and strategy in this increasingly important area of development theory and practice.
    Keywords: Development studies, Political economy, Public administration, and African Studies ; bic Book Industry Communication::G Reference, information & interdisciplinary subjects::GT Interdisciplinary studies::GTF Development studies ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy ; bic Book Industry Communication::J Society & social sciences::JP Politics & government::JPP Public administration ; bic Book Industry Communication::1 Geographical Qualifiers::1H Africa
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  • 10
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    The Future of Africa (2021)
    Springer Nature | Palgrave Macmillan
    Details
    Publication Date: 2024-03-29
    Description: This open access textbook offers a critical introduction to human and economic development prospects in Africa revolving around three questions: where is Africa today, what explains the current state, and, given historical trends and what we know about the world, where do we think the continent will be in 2040? And, a final question: what can we do to create a better tomorrow? It models ambitious progress in health, demographics, agriculture, education, industrialization, technological leapfrogging, increased trade, greater stability, better governance and external support. The book reviews the future of work/jobs, poverty and the impact of climate change. A combined Closing the Gap scenario presents a forecast of what could be possible by 2040. Each chapter suggests which policies might accelerate prospects for each sector. Written in an accessible style, and supported by a range of pedagogical features, this textbook introduces undergraduate and graduate students to the contemporary human and economic development prospects in Africa.
    Keywords: African Politics ; Development Studies ; Political Economy/Economic Systems ; Political Economy and Economic Systems ; Africa ; demographics ; population ; development ; development in Africa ; African Union ; China ; political economy in Africa ; Open access ; Politics & government ; Political economy ; bic Book Industry Communication::J Society & social sciences::JP Politics & government ; bic Book Industry Communication::G Reference, information & interdisciplinary subjects::GT Interdisciplinary studies::GTF Development studies ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy ; thema EDItEUR::J Society and Social Sciences::JP Politics and government ; thema EDItEUR::G Reference, Information and Interdisciplinary subjects::GT Interdisciplinary studies::GTP Development studies ; thema EDItEUR::K Economics, Finance, Business and Management::KC Economics::KCP Political economy
    Language: English
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  • 11
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    Policy Feedback (2022)
    Cambridge University Press
    Details
    Publication Date: 2022-08-09
    Description: This element explores early and more recent contributions of the policy feedback literature to clarify the meaning of this concept and its contribution to both political science and policy studies. This element also discusses the practical implications of policy feedback research through a discussion of its potential impact on policy design.
    Keywords: Public policy ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy ; bic Book Industry Communication::J Society & social sciences::JP Politics & government::JPP Public administration ; bic Book Industry Communication::J Society & social sciences::JP Politics & government::JPH Political structure & processes
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  • 12
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    Political Settlements and Development (2022)
    Oxford University Press
    Details
    Publication Date: 2022-09-06
    Description: Few concepts have captured the imagination of the conflict and development communities in recent years as powerfully as the idea of a ‘political settlement’. At its most ambitious, ‘political settlements analysis’ (PSA) promises to explain why conflicts occur and states collapse, the conditions for their successful rehabilitation, different developmental pathways from peace, and how to better fit development policy to country context. Yet despite the meteoric rise of the term and its tremendous promise, not all is well in the world of PSA. Rival definitions of the concept abound; there are disagreements about its scope and the way it should be used; a growing schism between conflict specialists and economists; basic concepts are ambiguous; and little progress has been made on measurement. This book consequently has three main aims. The first is to argue for a revised definition of a political settlement, capable of unifying its diverse strands. The second is to put the concept on a more solid theoretical and scientific footing, providing a method for measuring and categorizing political settlements, using both qualitative case studies and a large-n statistical analysis to illustrate its potential. And the third is to examine the implications of the findings for mainstream social science analysis and for policymakers.
    Keywords: Government Policy, Provision and Effects of Welfare Programmes, Economic Development, Development Planning and Policy, Rent-Seeking, Lobbying, Elections, Legislatures, and Voting Behavior, Bureaucracy, Administrative Processes in Public Organizations, Corruption, Conflict, Conflict Resolution, Alliances, Revolutions, Positive Analysis of Policy Formulation and Implementation, Political Economy ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCM Development economics & emerging economies ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCS Economic systems & structures
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  • 13
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    The Political Economy of Bank Regulation in Developing Countries (2021)
    Oxford University Press
    Details
    Publication Date: 2021-02-10
    Description: Why do governments in some developing countries implement international standards, while others do not? Focusing on the politics of bank regulation, this book develops a new framework to explain regulatory interdependence between countries in the core and the periphery of the global financial system. Drawing on in-depth analysis of eleven countries across Africa, Asia, and Latin America, it shows how financial globalization generates strong reputational and competitive incentives for developing countries to converge on international standards. Regulatory interdependence is generated by relations between regulators, politicians, and banks within developing countries, and international actors including investors, peer regulators, and international financial institutions. We explain why it is that some configurations of domestic politics and forms of integration into global finance generate convergence with international standards, while other configurations lead to divergence. This book contributes to our understanding of the ways in which governments and firms in the core of global finance powerfully shape regulatory politics in the periphery, and the ways in which peripheral governments and firms manoeuvre within the constraints and opportunities created by financial globalization
    Keywords: Africa ; Asia ; Latin America ; financial globalization ; regulatory interdependence ; international banking standards ; Basel I ; Basel II ; Basel III ; transnational policy networks ; bic Book Industry Communication::J Society & social sciences::JP Politics & government::JPA Political science & theory ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy ; bic Book Industry Communication::J Society & social sciences::JP Politics & government::JPB Comparative politics ; bic Book Industry Communication::G Reference, information & interdisciplinary subjects::GT Interdisciplinary studies::GTF Development studies ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCM Development economics & emerging economies
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  • 14
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    The Politics of Inclusive Development: Interrogating the Evidence (2021)
    Oxford University Press
    Details
    Publication Date: 2022-04-28
    Description: It is now widely accepted that politics plays a significant role in shaping the possibilities for inclusive development. However, the specific ways in which this happens across different types and forms of development, and in different contexts, remains poorly understood. This collection provides the state of the art review regarding what is currently known about the politics of inclusive development. Leading academics offer systematic reviews of how politics shapes development across multiple dimensions, including through growth, natural resource governance, poverty reduction, service delivery, social protection, justice systems, the empowerment of marginalized groups, and the role of both traditional and non-traditional donors. The book not only provides a comprehensive update but also a groundbreaking range of new directions for thinking and acting around these issues. The book’s originality thus derives not only from the wide scope of its case-study material, but also from the new conceptual approaches it offers for thinking about the politics of inclusive development, and the innovative and practical suggestions for donors, policymakers, and practitioners that flow from this.
    Keywords: citizenship ; transnational ; politics ; recognition ; inclusive development ; political settlement ; accumulation ; China ; Economic growth ; Ethnic group ; Welfare ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCB Macroeconomics ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCM Development economics & emerging economies ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy
    Language: English
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  • 15
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    Reviving Classical Liberalism Against Populism (2024)
    Springer Nature | Palgrave Macmillan
    Details
    Publication Date: 2024-03-14
    Description: This open access book by Nils Karlson explores the strategies used by left- and right-wing populists to make populism intelligible, recognizable, and contestable. It presents a synthesized explanatory model for how populists promote autocratization through the deliberate polarization of society. It traces the ideational roots of the core populist ideas and shows that these ideas form a collectivistic identity politics. Karlson argues that to fight back requires the revival of liberalism itself by defending and developing the liberal institutions, the liberal spirit, liberal narratives, and liberal statecraft.  The book also presents and discusses an extensive list of counterstrategies against populism.  Written within the tradition of political theory and institutional economics, this book uses a wide variety of sources, including results and analyses from social psychology, ethics, law, and history.
    Keywords: Classical Liberalism ; Populism ; Liberalism ; Liberal ; statecraft ; liberal politics ; identity politics ; political theory ; institutional economics ; bic Book Industry Communication::J Society & social sciences::JP Politics & government::JPA Political science & theory ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy ; bic Book Industry Communication::J Society & social sciences::JH Sociology & anthropology::JHB Sociology ; bic Book Industry Communication::J Society & social sciences::JP Politics & government
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  • 16
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    Made in Africa: (2021)
    Oxford University Press
    Details
    Publication Date: 2021-02-10
    Description: This book presents the findings of original field research into the design, practice, and varied outcomes of industrial policy in three sectors in Ethiopia, covering export-oriented and import-substitution industries. The three sectors are cement, leather and leather products, and floriculture. Given that there is a single industrial strategy, why do its outcomes vary across sectors? To what extent is this a function of the specific market and political economy features of each sector? The book examines industrial structures and associated global value chains to demonstrate the challenges faced by African firms in international markets. Part of the book’s relevance is the light it throws on the whole question of industrial policy in low-income countries, the subject of renewed discussion among development economists and organizations in recent years. The findings are also discussed in the light of the history of, and the history of thought about, industrialization. Insights for researchers and policymakers emerge from the analysis of failures and successes in the three industrial sectors. The book also challenges prevailing wisdom on how much and what kind of state intervention is required to support transformational industrial policy in Africa. Among other things, the book highlights the significance for policy design of maximizing linkage effects, backward and forward, from particular industries and activities.
    Keywords: development economics & emerging economies ; economics of industrial organisation ; political economy ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCM Development economics & emerging economies ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCD Economics of industrial organisation ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy
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  • 17
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    Reviving Classical Liberalism Against Populism (2024)
    Springer Nature | Palgrave Macmillan
    Details
    Publication Date: 2024-01-16
    Description: This open access book by Nils Karlson explores the strategies used by left- and right-wing populists to make populism intelligible, recognizable, and contestable. It presents a synthesized explanatory model for how populists promote autocratization through the deliberate polarization of society. It traces the ideational roots of the core populist ideas and shows that these ideas form a collectivistic identity politics. Karlson argues that to fight back requires the revival of liberalism itself by defending and developing the liberal institutions, the liberal spirit, liberal narratives, and liberal statecraft.  The book also presents and discusses an extensive list of counterstrategies against populism.  Written within the tradition of political theory and institutional economics, this book uses a wide variety of sources, including results and analyses from social psychology, ethics, law, and history.
    Keywords: Classical Liberalism ; Populism ; Liberalism ; Liberal ; statecraft ; liberal politics ; identity politics ; political theory ; institutional economics ; bic Book Industry Communication::J Society & social sciences::JP Politics & government::JPA Political science & theory ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy ; bic Book Industry Communication::J Society & social sciences::JH Sociology & anthropology::JHB Sociology
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  • 18
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    Dumbing Down (2022)
    Springer Nature | Palgrave Macmillan
    Details
    Publication Date: 2022-03-16
    Description: This open access book examines the challenges and issues caused by a move to a marketized education system in Sweden. Observing the introduction of the school voucher system and a postmodern social constructivist view of knowledge, the move away from objective knowledge is identified as the core reason for Sweden’s current education crisis. The impact of declining education standards on the labor market is also discussed. This book highlights the issues seen in Sweden and suggests policies that can improve education in the rest of the Western world as well. It will be relevant to students and researchers interested in education and labor economics.
    Keywords: Swedish Educational System ; Educational Performance in Swedish Schools ; Marketized Education ; Test Results and National Economic Performance ; Dysfunctional work environment ; Fragmentation of the Swedish School System ; Open Access ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCF Labour economics ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy
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  • 19
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    Consequences of the Global Financial Crisis (2021)
    Oxford University Press
    Details
    Publication Date: 2024-03-29
    Description: The Global Financial Crisis (GFC) is the most serious economic crisis since the Great Depression. Many books have explored its causes, but this book systematically explores its consequences. The focus is primarily on the policy and political consequences of the GFC. This book asks how governments responded to the challenge and what the political consequences of the combination of the GFC itself and policy responses to it have been. Based on workshops held in the United States and the United Kingdom, it brings together leading academics to consider the divergent ways in which particular countries have responded in different ways to the crisis, including China, France, the United Kingdom, and the United States. Part of what is happening is a structural shift in economic power from east to west, but China has its fragilities while Germany offers an example of a largely successful Western model. The book also assesses attempts to develop global economic governance and to reform financial regulation and looks critically at the role of credit rating agencies. Unlike earlier crises, no new paradigm has emerged to challenge existing ways of thinking, meaning that neoliberalism has emerged relatively unscathed. The crisis has lacked a coherent and innovative intellectual response and has been characterized by remarkable policy stability.
    Keywords: neoliberalism ; structural change ; financial regulation ; global financial crisis ; China ; International Monetary Fund ; Non-commercial activity ; United States ; bic Book Industry Communication::J Society & social sciences::JP Politics & government ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy ; bic Book Industry Communication::K Economics, finance, business & management::KJ Business & management ; thema EDItEUR::J Society and Social Sciences::JP Politics and government ; thema EDItEUR::K Economics, Finance, Business and Management::KC Economics::KCP Political economy ; thema EDItEUR::K Economics, Finance, Business and Management::KJ Business and Management
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  • 20
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    The Politics of Distributing Social Transfers (2022)
    Oxford University Press
    Details
    Publication Date: 2022-09-06
    Description: This book provides a systematic analysis of the political processes shaping the distribution of social transfers in six countries in sub-Saharan Africa and South Asia. In doing so, the book addresses a notable gap in recent research on social protection concerning the politics of implementation. While considerable attention has been devoted to debating the merits of different policy designs and the political factors shaping the adoption and diffusion of different policy models, ultimately the ability of any social transfer programme to deliver on its promises is dependent on the effective implementation and distribution of social transfers in line with intended objectives. The chapters in this book examine international and sub-national variation in programme implementation in Bangladesh, Ethiopia, Ghana, Kenya, Nepal, and Rwanda, drawing on a common analytical framework that highlights the importance of state capacity and reach, rooted in histories of state formation, and contemporary political competition in shaping the distribution of social transfers. Comparative analysis of the case studies supports the view that variation in the capacity and reach of the state within countries is a centrally important factor shaping the effectiveness and impartiality of distribution. Yet state capacity alone is insufficient. Rather, political competition and power relations shape how this capacity is actually deployed in practice. As such, the book underscores the inherently political nature of implementation and questions common technocratic efforts to improve implementation by de-politicizing the social protection policy process.
    Keywords: social protection, social transfer, policy implementation, political economy, power relations, state capacity, Africa, South Asia ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy ; bic Book Industry Communication::J Society & social sciences::JF Society & culture: general::JFF Social issues & processes ; bic Book Industry Communication::G Reference, information & interdisciplinary subjects::GT Interdisciplinary studies::GTF Development studies ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCM Development economics & emerging economies
    Language: English
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    New Sources of Development Finance (2021)
    Oxford University Press
    Details
    Publication Date: 2021-02-10
    Description: "As their Millennium Development Goals, world leaders have pledged by 2015 to halve the number of people living in extreme poverty and hunger, to achieve universal primary education, to reduce child mortality, to halt the spread of HIV/AIDS, and to halve the number of people without safe drinking water. Achieving these goals requires a large increase in the flow of financial resources to developing countries – double the present development assistance from abroad. In examining innovative ways to secure these resources, this book, which is part of the UNU–WIDER Studies in Development Economics series, sets out a framework for the economic analysis of different sources of funding and applying the tools of modern public economics to identify the key issues. It examines the role of new sources of overseas aid, considers the fiscal architecture and the lessons that can be learned from federal fiscal systems, asks how far increased transfers impose a burden on donors, and investigates how far the raising of resources can be separated from their use. In turn, the book examines global environmental taxes (such as a carbon tax), the taxation of currency transactions (the Tobin tax), a development‐focused allocation of Special Drawing Rights by the International Monetary Fund (IMF), the UK Government proposal for an International Finance Facility, increased private donations for development purposes, a global lottery (or premium bond), and increased remittances by emigrants. In each case, it considers the feasibility of the proposal and the resources that it can realistically raise, and offers new perspectives and insights into these new and controversial proposals. "
    Keywords: child mortality reduction ; development economics ; allocation of Special Drawing Rights by IMF ; development assistance ; development finance ; economic analysis ; environmental taxes ; federal fiscal systems ; funding ; global lottery ; global premium bond ; HIV/AIDS spread prevention ; hunger reduction ; International Finance Facility ; Millennium Development Goals ; poverty alleviation ; private donations ; remittances by emigrants ; safe drinking water ; sources of funding ; sources of overseas aid ; Special Drawing Rights ; taxation of currency transactions ; Tobin tax ; universal primary education ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCL International economics ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCM Development economics & emerging economies ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy ; bic Book Industry Communication::K Economics, finance, business & management::KF Finance & accounting::KFF Finance::KFFD Public finance::KFFD1 Taxation
    Language: English
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    Ageing and Health (2022)
    Cambridge University Press
    Details
    Publication Date: 2022-08-09
    Description: Ageing societies can be healthy and productive- if they get the politics right. This book argues that the population ageing crisis can be solved through policies that reduce inequalities between and within generations. It then explores the political coalitions needed to support policymaking that avoids pitting generations against each other.
    Keywords: economics of ageing ; politics of ageing ; healthy ageing ; ageing crisis ; health policy ; health systems ; healthcare management ; public policy ; public finance ; intergenerational justice ; welfare state ; pensions ; pension policy ; public health ; bic Book Industry Communication::K Economics, finance, business & management ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy
    Language: English
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    Making Global Policy (2022)
    Cambridge University Press
    Details
    Publication Date: 2022-08-09
    Description: This Element goes beyond traditional texts which focus on public policy as an activity of states to outline how global policy making has driven many global and regional transformations over the past quarter-century. This title is also available as Open Access on Cambridge Core.
    Keywords: public policy ; bic Book Industry Communication::J Society & social sciences::JP Politics & government::JPP Public administration ; bic Book Industry Communication::J Society & social sciences::JP Politics & government::JPA Political science & theory ; bic Book Industry Communication::J Society & social sciences::JP Politics & government::JPS International relations::JPSN International institutions ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy
    Language: English
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    Determinants of Financial Development (2021)
    Springer Nature | Palgrave Macmillan
    Details
    Publication Date: 2023-03-20
    Description: "As the world has witnessed the worst financial crisis and climate crisis of our age, during the period of 2007-2009, the issues surrounding the emergence and development of financial markets and carbon markets is becoming an increasingly significant area of research and debate worldwide. By engaging with recently developed methods of research and new areas of practice, this book investigates the political, economic, policy and geographic determinants of the development of financial markets. The volume examines the causality between financial development and aggregate private investment from an economic perspective. It also explores the consequences of political liberalization, focusing on the impact of institutional improvement on financial development. It studies what stimulates governments to initiate reforms aimed at boosting financial development, and analyses the determinants of carbon markets in developing countries from a geographic point of view. This book is essential reading for all interested in economic and financial development, climate change, environmental economics, and applied econometrics. "
    Keywords: reform ; financiele markten ; carbon ; development ; financial markets ; koolstof ; ontwikkeling ; hervorming ; crisis ; Democracy ; Dependent and independent variables ; Estimator ; Gross domestic product ; Long run and short run ; P-value ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCB Macroeconomics ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCM Development economics & emerging economies ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCN Environmental economics ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy ; bic Book Industry Communication::K Economics, finance, business & management::KF Finance & accounting::KFF Finance::KFFK Banking
    Language: English
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    When Can Oil Economies Be Deemed Sustainable? (2020)
    Springer Nature | Palgrave Macmillan
    Details
    Publication Date: 2021-12-24
    Description: This open access book questions the stereotype depicting all Gulf (GCC) economies as not sustainable, and starts a critical discussion of what these economies and polities should do to guarantee themselves a relatively stable future. Volatile international oil markets and the acceleration of the energy transition has challenged the notion that oil revenues are sufficient to sustain oil economies in the near to medium term. But what is the meaning of economic sustainability? The book discusses the multiple dimensions of the concept: economic diversification, continuing value of resources, taxation and fiscal development, labor market sustainability, sustainable income distribution, environmental sustainability, political order (democracy or authoritarianism) and sustainability, regional integration. The overarching message in this book is that we should move on from the simplistic branding of the Gulf economies as unsustainable and tackle the details of which adaptations they might need to undertake.
    Keywords: International Political Economy ; Sustainable Development ; Natural Resource and Energy Economics ; Energy Policy, Economics and Management ; Middle Eastern Politics ; Middle Eastern and North African Economics ; International Relations ; Environmental Social Sciences ; Environmental Economics ; Economy-wide Country Studies ; Open Access ; Sustainability of GCC Development ; New Global Oil Order ; Economic sustainability in resource-rich states ; Gulf Economic Diversification and Sustainable Development ; Political Economy of Diversification ; Economic Transformation vs. Diversification ; Oil and Economic Diversification ; Fiscal dimensions of Economic Sustainability ; Labour Market dimensions of Economic Sustainability ; Hydrocarbon Endowment in the Gulf Region ; Normalizing the Saudi Economy ; Inclusive Growth in the Gulf Region ; Saudi Private Sector’s Contribution to Fiscal Sustainability ; Economic Sustainability and the Energy Transition ; Economic Diversification in the MENA ; Peak Oil and the Energy Transition in the MENA ; Economic Diversification Through Energy Sector Reform ; Energy Pricing Reform in the Gulf Region ; Climate Strategy for Producer Countries ; Political economy ; Sustainability ; Environmental economics ; Energy technology & engineering ; Energy industries & utilities ; Politics & government ; Middle East ; Economics ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy ; bic Book Industry Communication::R Earth sciences, geography, environment, planning::RN The environment::RNU Sustainability ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCN Environmental economics ; bic Book Industry Communication::T Technology, engineering, agriculture::TH Energy technology & engineering ; bic Book Industry Communication::J Society & social sciences::JP Politics & government ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics
    Language: English
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    Governing Social Protection in the Long Term (2021)
    Springer Nature | Palgrave Macmillan
    Details
    Publication Date: 2021-02-10
    Description: This open access book examines the comparative evolution of social protection in Australia and New Zealand from 1890 to the present day, focusing on the relationship between employment relations and social policy. Utilising longstanding and more recent developments in historical institutionalist methodology, Ramia investigates the relationship between these two policy domains in the context of social protection theory. He argues that treating employment relations as dynamic, and as inextricably intertwined with changes in the welfare state over time, allows for more accurate portrayal of similarity and difference in social protection. The book will be of most interest to researchers, advanced undergraduate and postgraduate students in social policy, employment relations, public policy, social and political history, and comparative politics.
    Keywords: Social Policy ; Sociology of Work ; Political Sociology ; social harm ; the free market ; employment and welfare ; labour market ; industrial relations ; Open access ; Political economy ; Social & ethical issues ; Sociology: work & labour ; Sociology ; Politics & government ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy ; bic Book Industry Communication::J Society & social sciences::JH Sociology & anthropology::JHB Sociology::JHBL Sociology: work & labour ; bic Book Industry Communication::J Society & social sciences::JH Sociology & anthropology::JHB Sociology
    Language: English
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    Transnational Solidarity in Times of Crises (2021)
    Springer Nature | Palgrave Macmillan
    Details
    Publication Date: 2021-02-10
    Description: This open access collection is devoted to an in-depth, qualitative analysis of practices of cross-national solidarity in response to the current political and social crises, from citizens’ initiatives to networks of cooperation among civil society actors. The book analyses existing informal groups at the grassroots, furthering transnational solidarity in three thematic areas: disability, unemployment and immigration. Contributions assess how civic groups respond to the various crises affecting Europe, especially the economic and refugee crises, presenting new findings from a systematic comparative study conducted in eight European countries (Denmark, France, Germany, Greece, Italy, Poland, Switzerland, and the UK). The research will be of interest to scholars, students, journalists, policy-makers and activists interested in civil society, social movements, charitable actions, altruism and solidarity, as well as European studies and the socio-economic challenges of current European crises.
    Keywords: Political Sociology ; Social Sciences, general ; Migration ; Social Policy ; Sociology of Organizations and Occupations ; Sociology of Migration ; European Studies ; Social movements ; Activism ; volunteering ; Disability ; Unemployment ; Immigration ; Open Access ; Sociology ; Politics & government ; Society & Social Sciences ; Migration, immigration & emigration ; Political economy ; Social & ethical issues ; bic Book Industry Communication::J Society & social sciences::JH Sociology & anthropology::JHB Sociology ; bic Book Industry Communication::J Society & social sciences ; bic Book Industry Communication::J Society & social sciences::JF Society & culture: general::JFF Social issues & processes::JFFN Migration, immigration & emigration ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy
    Language: English
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    Deals and Development (2021)
    Oxford University Press
    Details
    Publication Date: 2024-03-29
    Description: "International financial crises have plagued the world in recent decades, including the Latin American debt crisis of the 1980s, the East Asian crisis of the late twentieth century, and the global financial crisis of 2007-09. One of the basic problems faced during these crises is the lack of adequate preventive mechanisms, as well as insufficient instruments to finance countries in crisis and to overcome their over-indebtedness. Resetting the International Monetary (Non)System provides an analysis of the global monetary system and the necessary reforms that it should undergo to play an active role in the twenty-first century and proposes a comprehensive yet evolutionary reform of the system. Criticising the ad hoc framework- a ""(non)system""- that has evolved following the breakdown of the Bretton Woods arrangement in the early 1970's, Resetting the International Monetary (Non)System places a special focus on the asymmetries that emerging and developing countries face, analysing the controversial management of crises by the International Monetary Fund and proposing a consistent set of reform proposals to design a better system of international monetary cooperation. Policy orientated and structured to deal in a sequential way with the issues involved, it suggests provision of international liquidity through a system that mixes the multicurrency arrangement with a more active use of the IMF's Special Drawing Rights; stronger mechanisms of macroeconomic policy cooperation, including greater cooperation in exchange rate management and freedom to manage capital flows; additional automatic balance-of-payments financing facilities and the complementary use of swap and regional arrangements; a multilateral sovereign debt workout mechanism; and major reforms of the system's governance."
    Keywords: economics ; monetary economics ; Ghana ; Gross domestic product ; Liberia ; Malaysia ; Thailand ; Uganda ; bic Book Industry Communication::J Society & social sciences::JP Politics & government ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCG Economic growth ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCM Development economics & emerging economies ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy ; thema EDItEUR::J Society and Social Sciences::JP Politics and government ; thema EDItEUR::K Economics, Finance, Business and Management::KC Economics ; thema EDItEUR::K Economics, Finance, Business and Management::KC Economics::KCG Economic growth ; thema EDItEUR::K Economics, Finance, Business and Management::KC Economics::KCM Development economics and emerging economies ; thema EDItEUR::K Economics, Finance, Business and Management::KC Economics::KCP Political economy
    Language: English
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    A City Cannot Be a Work of Art (2023)
    Springer Nature | Palgrave Macmillan
    Details
    Publication Date: 2023-11-16
    Description: This open access book connects Jane Jacobs's celebrated urban analysis to her ideas on economics and social theory. While Jacobs is a legend in the field of urbanism and famous for challenging and profoundly influencing urban planning and design, her theoretical contributions – although central to her criticisms of and proposals for public policy – are frequently overlooked even by her most enthusiastic admirers. This book argues that Jacobs’s insight that “a city cannot be a work of art” underlies both her ideas on planning and her understanding of economic development and social cooperation. It shows how the theory of the market process and Jacobs’s theory of urban processes are useful complements – an example of what economists and urbanists can learn from each other. This Jacobs-cum-market-process perspective offers new theoretical, historical, and policy analyses of cities, more realistic and coherent than standard accounts by either economists or urbanists.
    Keywords: social theory ; spontaneous order ; entrepreneurship ; Jane Jacobs ; urban design ; urbanism ; diversity ; innovation ; living city ; economic development ; social capital ; social networks ; action space ; urban planning ; bic Book Industry Communication::R Earth sciences, geography, environment, planning::RG Geography::RGC Human geography ; bic Book Industry Communication::J Society & social sciences::JH Sociology & anthropology::JHB Sociology::JHBA Social theory ; bic Book Industry Communication::J Society & social sciences::JP Politics & government::JPP Public administration ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics ; bic Book Industry Communication::J Society & social sciences::JH Sociology & anthropology::JHB Sociology ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy
    Language: English
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    Remittances as Social Practices and Agents of Change (2023)
    Springer Nature | Palgrave Macmillan
    Details
    Publication Date: 2023-11-17
    Description: This open access book explores the transformative effects of remittances. Remittances are conceptualized as flows of money, objects, ideas, traditions, and symbolic capital, mapping out a cross-border space in which people live, work, and communicate with multiple belongings. By doing so, they effect social change both in places of origin and destination. However, their power to improve individual living conditions and community infrastructure mainly results from global inequality. Hence, we challenge the remittance mantra and go beyond the migration-development-nexus by revealing dependencies and frictions in remittance relations. Remittances are thus scrutinized in their effects on both social cohesion and social rupture. By highlighting the transformative effects of remittance in the context of conflict, climate change, and the postcolonial, we shed light on the future of transnational society. Presenting empirical case studies from Ghana, Burkina Faso, Sri Lanka, New Zealand, Turkey, Lebanon, USA, Japan, and various European countries, as well as historical North America and the Habsburg Empire, we explore remittance relations from a range of disciplines including anthropology, sociology, history, design, architecture, governance, and peace studies.
    Keywords: transnationalism ; migration ; economy ; political economy ; charity ; financial remittances ; gift ; exchange ; cultural exchange ; bic Book Industry Communication::J Society & social sciences::JF Society & culture: general::JFF Social issues & processes::JFFN Migration, immigration & emigration ; bic Book Industry Communication::J Society & social sciences::JH Sociology & anthropology::JHB Sociology ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCM Development economics & emerging economies
    Language: English
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    How Nations Learn (2021)
    Oxford University Press
    Details
    Publication Date: 2021-02-10
    Description: Authored by eminent scholars, the volume aims to generate interest and debate among policymakers, practitioners, and researchers on the complexity of learning and catch-up, particularly for twenty-first century late-late developers. The volume explores technological learning at the firm level, policy learning by the state, and the cumulative and multifaceted nature of the learning process, which encompasses learning by doing, by experiment, emulation, innovation, and leapfrogging. Why is catch-up rare? And why have some nations succeeded while others failed? What are the prospects for successful learning and catch-up in the twenty-first century? These are pertinent questions that require further research and in-depth analysis. The World Bank estimates that out of the 101 middle-income economies in 1960, only thirteen became high income by 2008. This volume examines how nations learn by reviewing key structural and contingent factors that contribute to dynamic learning and catch-up. Rejecting both the one-size-fits-all approach and the agnosticism that all nations are unique and different, the volume uses historical as well as firm-level, industry-level, and country-level evidence and experiences to identify the sources and drivers of successful learning and catch-up and the lessons for late-latecomer countries. Building on the latecomer-advantage perspective, the volume shows that what is critical for dynamic learning and catch-up is not learning per se but the intensity of learning, robust industrial policies, and the pace and direction of learning. Equally important are the passion to learn, long-term strategic vision, and understanding the context in which successful learning occurs.
    Keywords: catch-up ; technological learning ; industrial policy ; latecomers ; intensity of learning ; policy learning ; emualation ; innovation ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCG Economic growth ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCM Development economics & emerging economies ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy ; bic Book Industry Communication::K Economics, finance, business & management::KN Industry & industrial studies
    Language: English
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    The Japanese Banking Crisis (2021)
    Springer Nature | Palgrave Macmillan
    Details
    Publication Date: 2021-02-10
    Description: This open access book provides a readable narrative of the bubbles and the banking crisis Japan experienced during the two decades between the late 1980s and the early 2000s. Japan, which was a leading competitor in the world’s manufacturing sector, tried to transform itself into an economy with domestic demand-led mature growth, but the ensuing bubbles and crisis instead made the country suffer from chronicle deflation and stagnation. The book analyses why the Japanese authorities could not avoid making choices that led to this outcome. The chapters are based on the lectures to regulators from emerging economies delivered at the Global Financial Partnership Center of the Financial Services Agency of Japan.
    Keywords: Macroeconomics/Monetary Economics//Financial Economics ; Development Finance ; Economic History ; Political Economy/Economic Systems ; Macroeconomics and Monetary Economics ; Political Economy and Economic Systems ; Japanese banking crisis ; Financial Stability ; Banking Regulation in Japan ; Financial Crisis Management in Japan ; Japanese Economy ; Macro-prudential Policy ; Japanese financial cycle of 1986-2003 ; Open Access ; Macroeconomics ; Monetary economics ; Finance ; Development economics & emerging economies ; Political economy ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCB Macroeconomics ; bic Book Industry Communication::K Economics, finance, business & management::KF Finance & accounting::KFF Finance ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCZ Economic history ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy
    Language: English
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    On the response of the Earth to a fault system: its evaluation beyond the epicentral reference frame (2015)
    Oxford University Press
    Details
    Publication Date: 2015-09-24
    Description: Previous formalisms for determining the static perturbation of spherically symmetric self-gravitating elastic Earth models due to displacement dislocations deal with each infinitesimal element of the fault system in its epicentral reference frame. In this work, we overcome this restriction and present novel and compact formulas for obtaining the perturbation due to the whole fault system in an arbitrary and common reference frame. Furthermore, we show that, even in an arbitrary reference frame, it is still possible to discriminate the contributions associated with the polar, bipolar and quadrupolar patterns of the seismic source response, as well as their relation with the along strike, along dip and tensile components of the displacement dislocation. These results allow a better understanding of the relation between the static perturbation and the whole fault system, and find direct applications in geodetic problems, like the modelling of long-wavelength geoid or gravity data from GRACE and GOCE space missions and of the perturbation of the deviatoric inertia tensor of the Earth.
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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    A simple pendulum borehole tiltmeter based on a triaxial optical-fibre displacement sensor (2015)
    Oxford University Press
    Details
    Publication Date: 2015-09-26
    Description: Sensitive instruments like strainmeters and tiltmeters are necessary for measuring slowly varying low amplitude Earth deformations. Nonetheless, laser and fibre interferometers are particularly suitable for interrogating such instruments due to their extreme precision and accuracy. In this paper, a practical design of a simple pendulum borehole tiltmeter based on laser fibre interferometric displacement sensors is presented. A prototype instrument has been constructed using welded borosilicate with a pendulum length of 0.85 m resulting in a main resonance frequency of 0.6 Hz. By implementing three coplanar extrinsic fibre Fabry-Perot interferometric probes and appropriate signal filtering, our instrument provides tilt measurements that are insensitive to parasitic deformations caused by temperature and pressure variations. This prototype has been installed in an underground facility (Rustrel, France) where results show accurate measurements of Earth strains derived from Earth and ocean tides, local hydrologic effects, as well as local and remote earthquakes. The large dynamic range and the high sensitivity of this tiltmeter render it an invaluable tool for numerous geophysical applications such as transient fault motion, volcanic strain and reservoir monitoring.
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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    Constraints provided by ground gravity observations on geocentre motions (2016)
    Oxford University Press
    Details
    Publication Date: 2016-07-08
    Description: The geocentre motion is the motion of the centre of mass of the entire Earth, considered an isolated system, in a terrestrial system of reference. We first derive a formula relating the harmonic degree-1 Lagrangian variation of the gravity at a station to both the harmonic degree-1 vertical displacement of the station and the displacement of the whole Earth's centre of mass. The relationship is independent of the nature of the Earth deformation and is valid for any source of deformation. We impose no constraint on the system of reference, except that its origin must initially coincide with the centre of mass of the spherically symmetric Earth model. Next, we consider the geocentre motion caused by surface loading. In a system of reference whose origin is the centre of mass of the solid Earth, we obtain a specific relationship between the gravity variation at the surface, the geocentre displacement and the load Love number $h^{\prime }_1$ , which demands the Earth's structure and rheological behaviour be known. For various networks of real or fictitious stations, we invert synthetic signals of surface gravity variations caused by atmospheric loading to retrieve the degree-1 variation of gravity. We then select six well-distributed stations of the Global Geodynamics Project, which is a world network of superconducting gravimeters, to invert actual gravity data for the degree-1 variations and determine the geocentre displacement between the end of 2004 and the beginning of 2012, assuming it to be due to surface loading. We find annual and semi-annual displacements with amplitude 0.5–2.3 mm.
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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    On computing the geoelastic response to a disk load (2016)
    Oxford University Press
    Details
    Publication Date: 2016-05-05
    Description: We review the theory of the Earth's elastic and gravitational response to a surface disk load. The solutions for displacement of the surface and the geoid are developed using expansions of Legendre polynomials, their derivatives and the load Love numbers. We provide a matlab  function called diskload that computes the solutions for both uncompensated and compensated disk loads. In order to numerically implement the Legendre expansions, it is necessary to choose a harmonic degree, n max , at which to truncate the series used to construct the solutions. We present a rule of thumb (ROT) for choosing an appropriate value of n max , describe the consequences of truncating the expansions prematurely and provide a means to judiciously violate the ROT when that becomes a practical necessity.
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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    Constraints on seasonal load variations and regional rigidity from continuous GPS measurements in Iceland, 1997-2014 (2016)
    Oxford University Press
    Details
    Publication Date: 2016-05-06
    Description: Two types of signals are clearly visible in continuous GPS (cGPS) time-series in Iceland, in particular in the vertical component. The first one is a yearly seasonal cycle, usually sinusoid-like with a minimum in the spring and a maximum in the fall. The second one is a trend of uplift, with higher values the closer the cGPS stations are to the centre of Iceland and ice caps. Here, we study the seasonal cycle signal by deriving its average at 71 GPS sites in Iceland. We estimate the annual and semi-annual components of the cycle in their horizontal and vertical components using a least-squares adjustment. The peak-to-peak amplitude of the cycle of the vertical component at the studied sites ranges from 4 mm near the coastline up to 27 mm at the centre of the Vatnajökull, the largest ice cap in Iceland. The minimum of the seasonal cycle occurs earlier in low lying areas than in the central part of Iceland, consistent with snow load having a large influence on seasonal deformation. Modelling shows that the seasonal cycle is well explained by accounting for elastically induced surface displacements due to snow, atmosphere, reservoir lake and ocean variations. Model displacement fields are derived considering surface loads on a multilayered isotropic spherical Earth. Through forward and inverse modelling, we were able to reproduce a priori information on the average seasonal cycle of known loads (atmosphere, snow in non-glaciated areas and lake reservoir) and get an estimation of other loads (glacier mass balance and ocean). The seasonal glacier mass balance cycle in glaciated areas and snow load in non-glaciated areas are the main contributions to the seasonal deformation. For these loads, induced seasonal vertical displacements range from a few millimetres far from the loads in Iceland, to more than 20 mm at their centres. Lake reservoir load also has to be taken into account on local scale as it can generate up to 20 mm of vertical deformation. Atmosphere load and ocean load are observable and generate vertical displacements in the order of a few millimetres. Inversion results also shows that the Iceland crust is less rigid than the world average. Interannual deviation from the GPS seasonal cycle can occur and are caused by unusual weather conditions over extended period of time.
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
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    Topics: Geosciences
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    Optimization of regional constraints for estimating the Greenland mass balance with GRACE level-2 data (2015)
    Oxford University Press
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    Publication Date: 2015-05-03
    Description: Data from the Gravity Recovery and Climate Experiment (GRACE) satellite mission can be used to estimate the mass change rate for separate drainage systems (DSs) of the Greenland Ice Sheet (GrIS). One approach to do so is by inversion of the level-2 spherical harmonic data to surface mass changes in predefined regions, or mascons. However, the inversion can be numerically unstable for some individual DSs. This occurs mainly for DSs with a small mass change signal that are located in the interior region of Greenland. In this study, we present a modified mascon inversion approach with an improved implementation of the constraint equations to obtain better estimates for individual DSs. We use separate constraints for mass change variability in the coastal zone, where run-off takes place, and for the ice sheet interior above 2000 m, where mass changes are smaller. A multi-objective optimization approach is used to find optimal prior variances for these two areas based on a simulation model. Correlations between adjacent DSs are suppressed when our optimized prior variances are used, while the mass balance estimates for the combination of the DSs that make up the GrIS above 2000 m are not affected significantly. The resulting mass balance estimates for some DSs in the interior are significantly improved compared to an inversion with a single constraint, as determined by a comparison with mass balance estimates from surface mass balance modelling and discharge measurements. The rate of mass change of the GrIS for the period of January 2003 to December 2012 is found to be –266.1 ± 17.2 Gt yr –1 in the coastal zone and areas below 2000 m, and +8.2 ± 8.6 Gt yr –1 in the interior region.
    Keywords: Gravity, Geodesy and Tides
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    Topics: Geosciences
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    Integrated velocity field from ground and satellite geodetic techniques: application to Arenal volcano (2014)
    Oxford University Press
    Details
    Publication Date: 2014-12-17
    Description: Measurements of ground deformation can be used to identify and interpret geophysical processes occurring at volcanoes. Most studies rely on a single geodetic technique, or fit a geophysical model to the results of multiple geodetic techniques. Here we present a methodology that combines GPS, Total Station measurements and InSAR into a single reference frame to produce an integrated 3-D geodetic velocity surface without any prior geophysical assumptions. The methodology consists of five steps: design of the network, acquisition and processing of the data, spatial integration of the measurements, time series computation and finally the integration of spatial and temporal measurements. The most significant improvements of this method are (1) the reduction of the required field time, (2) the unambiguous detection of outliers, (3) an increased measurement accuracy and (4) the construction of a 3-D geodetic velocity field. We apply this methodology to ongoing motion on Arenal's western flank. Integration of multiple measurement techniques at Arenal volcano revealed a deformation field that is more complex than that described by individual geodetic techniques, yet remains consistent with previous studies. This approach can be applied to volcano monitoring worldwide and has the potential to be extended to incorporate other geodetic techniques and to study transient deformation.
    Keywords: Gravity, Geodesy and Tides
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    On the decorrelation filtering of RL05 GRACE data for global applications (2014)
    Oxford University Press
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    Publication Date: 2014-11-09
    Description: In autumn 2012, the new release 05 (RL05) of monthly geopotencial spherical harmonics Stokes coefficients (SC) from Gravity Recovery and Climate Experiment (GRACE) mission was published. This release reduces the noise in high degree and order SC, but they still need to be filtered. One of the most common filtering processing is the combination of decorrelation and Gaussian filters. Both of them are parameters dependent and must be tuned by the users. Previous studies have analyzed the parameters choice for the RL05 GRACE data for oceanic applications, and for RL04 data for global application. This study updates the latter for RL05 data extending the statistics analysis. The choice of the parameters of the decorrelation filter has been optimized to: (1) balance the noise reduction and the geophysical signal attenuation produced by the filtering process; (2) minimize the differences between GRACE and model-based data and (3) maximize the ratio of variability between continents and oceans. The Gaussian filter has been optimized following the latter criteria. Besides, an anisotropic filter, the fan filter, has been analyzed as an alternative to the Gauss filter, producing better statistics.
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
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    Topics: Geosciences
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    Transient gravity perturbations induced by earthquake rupture (2015)
    Oxford University Press
    Details
    Publication Date: 2015-04-06
    Description: The static and transient deformations produced by earthquakes cause density perturbations which, in turn, generate immediate, long-range perturbations of the Earth's gravity field. Here, an analytical solution is derived for gravity perturbations produced by a point double-couple source in homogeneous, infinite, non-self-gravitating elastic media. The solution features transient gravity perturbations that occur at any distance from the source between the rupture onset time and the arrival time of seismic P waves, which are of potential interest for real-time earthquake source studies and early warning. An analytical solution for such prompt gravity perturbations is presented in compact form. We show that it approximates adequately the prompt gravity perturbations generated by strike-slip and dip-slip finite fault ruptures in a half-space obtained by numerical simulations based on the spectral element method. Based on the analytical solution, we estimate that the observability of prompt gravity perturbations within 10 s after rupture onset by current instruments is severely challenged by the background microseism noise but may be achieved by high-precision gravity strainmeters currently under development. Our analytical results facilitate parametric studies of the expected prompt gravity signals that could be recorded by gravity strainmeters.
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
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    Topics: Geosciences
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    Transient gravity perturbations from a double-couple in a homogeneous half-space (2016)
    Oxford University Press
    Details
    Publication Date: 2016-04-03
    Description: Seismic waves produced by fault ruptures give rise to gravity perturbations. So far, these perturbations have either been modelled as permanent coseismic gravity change in a half-space or spherical Earth model, or as full time-domain model in infinite space. In this paper, we present the explicit solution of gravity perturbations in time domain produced by a double-couple buried in a homogeneous half-space. This result is especially suited to study gravity perturbations up to a few hundreds of kilometres from the epicentre. It facilitates detailed parametric studies of gravity perturbations from fault rupture, and predicts gravity perturbations of real earthquakes with greatly improved accuracy. The results may serve to develop first designs of gravity-assisted earthquake early-warning systems, made possible by a new generation of ultrasensitive gravity gradiometers, which is currently under development.
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
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    Topics: Geosciences
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    Five years gravity observation with the superconducting gravimeter OSG#058 at Syowa Station, East Antarctica: gravitational effects of accumulated snow mass (2016)
    Oxford University Press
    Details
    Publication Date: 2016-04-07
    Description: Continuous gravimetric observations have been made with three successive generations of superconducting gravimeter over 20 yr at Syowa Station ( $39.6\deg$ E, $69.0\deg$ S), East Antarctica. The third-generation instrument, OSG#058, was installed in January 2010 and was calibrated by an absolute gravimeter during January and February, 2010. The estimated scale factor was –73.823 ± 0.053 μGal V –1 (1 μGal = 10 –8 m s –2 ). The first 5 yr of OSG#058 data from 2010 January 7 to 2015 January 10 were decomposed into tidal waves (M3 to Ssa) and other non-tidal components by applying the Bayesian tidal analysis program BAYTAP. Long-term non-tidal gravity residuals, which were obtained by subtracting annual and 18.6 year tidal waves and the predicted gravity response to the Earth's variable rotation, showed significant correlation with the accumulated snow depth measured at Syowa Station. The greatest correlation occurred when the gravity variations lagged the accumulated snow depth by 21 d. To estimate the gravitational effect of the accumulated snow mass, we inferred a conversion factor of 3.13 ± 0.08 μGal m –1 from this relation. The accumulated snow depth at Syowa Station was found to represent an extensive terrestrial water storage (the snow accumulation) around Syowa Station, which was estimated from the Gravity Recovery and Climate Experiment satellite gravity data. The snow accumulation around Syowa Station was detectable by the superconducting gravimeter.
    Keywords: Gravity, Geodesy and Tides
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    AIUB-RL02: an improved time-series of monthly gravity fields from GRACE data (2016)
    Oxford University Press
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    Publication Date: 2016-04-07
    Description: The new release AIUB-RL02 of monthly gravity models from GRACE GPS and K-Band range-rate data is based on reprocessed satellite orbits referring to the reference frame IGb08. The release is consistent with the IERS2010 conventions. Improvements with respect to its predecessor AIUB-RL01 include the use of reprocessed (RL02) GRACE observations, new atmosphere and ocean dealiasing products (RL05), an upgraded ocean tide model (EOT11A), and the interpolation of shallow ocean tides (admittances). The stochastic parametrization of AIUB-RL02 was adapted to include daily accelerometer scale factors, which drastically reduces spurious signal at the 161 d period in C 20 and at other low degree and order gravity field coefficients. Moreover, the correlation between the noise in the monthly gravity models and solar activity is considerably reduced in the new release. The signal and the noise content of the new AIUB-RL02 monthly gravity fields are studied and calibrated errors are derived from their non-secular and non-seasonal variability. The short-period time-variable signal over the oceans, mostly representing noise, is reduced by 50 per cent with respect to AIUB-RL01. Compared to the official GFZ-RL05a and CSR-RL05 monthly models, the AIUB-RL02 stands out by its low noise at high degrees, a fact emerging from the estimation of seasonal variations for selected river basins and of mass trends in polar regions. Two versions of the monthly AIUB-RL02 gravity models, with spherical harmonics resolution of degree and order 60 and 90, respectively, are available for the time period from March 2003 to March 2014 at the International Center for Global Earth Models or from ftp://ftp.unibe.ch/aiub/GRAVITY/GRACE (last accessed 22 March 2016).
    Keywords: Gravity, Geodesy and Tides
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    Accounting for time- and space-varying changes in the gravity field to improve the network adjustment of relative-gravity data (2015)
    Oxford University Press
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    Publication Date: 2015-12-13
    Description: The relative gravimeter is the primary terrestrial instrument for measuring spatially and temporally varying gravitational fields. The background noise of the instrument—that is, non-linear drift and random tares—typically requires some form of least-squares network adjustment to integrate data collected during a campaign that may take several days to weeks. Here, we present an approach to remove the change in the observed relative-gravity differences caused by hydrologic or other transient processes during a single campaign, so that the adjusted gravity values can be referenced to a single epoch. The conceptual approach is an example of coupled hydrogeophysical inversion, by which a hydrologic model is used to inform and constrain the geophysical forward model. The hydrologic model simulates the spatial variation of the rate of change of gravity as either a linear function of distance from an infiltration source, or using a 3-D numerical groundwater model. The linear function can be included in and solved for as part of the network adjustment. Alternatively, the groundwater model is used to predict the change of gravity at each station through time, from which the accumulated gravity change is calculated and removed from the data prior to the network adjustment. Data from a field experiment conducted at an artificial-recharge facility are used to verify our approach. Maximum gravity change due to hydrology (observed using a superconducting gravimeter) during the relative-gravity field campaigns was up to 2.6 μGal d –1 , each campaign was between 4 and 6 d and one month elapsed between campaigns. The maximum absolute difference in the estimated gravity change between two campaigns, two months apart, using the standard network adjustment method and the new approach, was 5.5 μGal. The maximum gravity change between the same two campaigns was 148 μGal, and spatial variation in gravity change revealed zones of preferential infiltration and areas of relatively high groundwater storage. The accommodation for spatially varying gravity change would be most important for long-duration campaigns, campaigns with very rapid changes in gravity and (or) campaigns where especially precise observed relative-gravity differences are used in the network adjustment.
    Keywords: Gravity, Geodesy and Tides
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    Traveling ionospheric disturbances propagating ahead of the Tohoku-Oki tsunami: a case study (2016)
    Oxford University Press
    Details
    Publication Date: 2016-01-01
    Description: We document two kinds of traveling ionospheric disturbances, namely, CTIDs (Co-tsunami-Traveling-Ionospheric-disturbances) and ATIDs (Ahead-of-Tsunami-Traveling-Ionospheric-disturbances) related to the Tohoku-Oki tsunami of 2011 March 11. They are referred to the disturbances that remain behind and ahead of the principal tsunami wave front, respectively. We first note their presence in a numerical experiment performed using a simulation code coupling the tsunami, atmosphere and ionosphere. This code uses the tsunami wavefield as an input and simulates acoustic-gravity waves (AGWs) in the atmosphere and TIDs, in the form of total electron content (TEC) disturbance, in the ionosphere. The simulated TEC reveals the excitation of CTIDs (at about 2 TECU) and ATIDs (at about 1 TECU), representing up to 5 per cent disturbance over the ambient electron density, and they arise from the dissipation of AGWs in the thermosphere. A novel outcome is that during the tsunami passage between ~6° and 12° of epicentral distance, strong ATIDs arrive ~20–60 min ahead of the tsunami wave front covering ~3°–10° of distance from the tsunami location. Simulation results are compared with the far-field observations using GNSS satellites and confirm that ATIDs are the first detected TEC maximum, occurring 20–60 min ahead of the tsunami arrival. Our simulation also confirms the presence of largest TEC maximum representing CTIDs, 10–20 min after the first tsunami wave. ATIDs reported in this study have characteristics that can be potentially used for the early warning of the tsunami.
    Keywords: Gravity, Geodesy and Tides
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    Geological units and Moho depth determination in the Western Balkans exploiting GOCE data (2015)
    Oxford University Press
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    Publication Date: 2015-06-20
    Description: In the present work we illustrate a new local inversion algorithm to retrieve the Moho depth from GOCE (Gravity field and steady-state Ocean Circulation Explorer) gravity field. In details the proposed procedure can be divided into two main steps: the first one consists in recognizing and isolating the different geological provinces in the study area by exploiting information coming from the GOCE global gravity field model. Once the main geological provinces are defined, a function relating the crust density of each province with depth is built and used to reduce the data. The gravitational effects of sediments, topography, bathymetry and upper mantle are also removed. In the second step the residual gravitational field is inverted to retrieve the Moho depth and some information on the crustal density. In particular, the clustering of geological province is performed by means of an automatic Bayesian classification algorithm while the inversion of GOCE residual field is performed by adapting the global algorithm developed in the framework of the GEMMA project to the local scale. The procedure, based on an iterative Wiener filter, allows to compute the Moho depth considering lateral as well as radial variations of crustal density. The algorithm has been applied to the fifth release of GOCE time-wise global gravity field model to infer information on the crustal structure in the Western Balkan area, that is, the region laying between Bulgaria and the Adriatic Sea. This region is one of the most complex and active, from the tectonic point of view, in the whole Europe and it is characterized by the presence of the Alpine-Himalayan orogenic belt, formed by the collision between the African and Eurasian plates, and by the opening of the Pannonian Basin. Results show a good agreement between the obtained geological provinces with the actual knowledge on the region. The resulting Moho depth ranges between about 20 km beneath the Adriatic Sea and 45 km in the Dinarides. Comparisons with available seismic data show differences smaller than 1 km (standard deviation).
    Keywords: Gravity, Geodesy and Tides
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    Decadal and quadratic variations of Earth's oblateness and polar ice mass balance from 1979 to 2010 (2015)
    Oxford University Press
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    Publication Date: 2015-08-29
    Description: Gravity variations associated with Earth's oblateness ( J 2 ) have been observed by satellite laser ranging (SLR) since 1976. The J 2 time-series has been used to measure and help understand many geophysical processes within the Earth system ranging from the mantle to the atmosphere. While post glacial rebound and the Earth climate system are believed to be the primary driving forces of long-term and seasonal J 2 variations, the physical cause of decadal and longer timescale J 2 variations has remained uncertain, although recent evidence indicates that polar ice mass changes are important. In this study, we estimate a variety of climate contributions to J 2 over the period 1979–2010, and find that ice mass variations in Greenland and Antarctica are the dominant cause of observed decadal and longer J 2 variations. Residual variations at periods near 10–11 years may reflect limitations of numerical climate models in estimating mass change variability at long periods, but are also suggestive of potential contribution related to variable solar activity.
    Keywords: Gravity, Geodesy and Tides
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    Calibrating interferometric synthetic aperture radar (InSAR) images with regional GPS network atmosphere models (2015)
    Oxford University Press
    Details
    Publication Date: 2015-07-30
    Description: Interferometric synthetic aperture radar (InSAR) technology provides a valuable tool for obtaining Earth surface deformation and topography at high spatial resolution for crustal deformation studies. Similar to global positioning system (GPS), InSAR measurements are affected by the Earth's ionospheric and tropospheric layers as the electromagnetic signals significantly refract while propagating through the different layers. While GPS signals propagating through the neutral atmosphere are affected primarily by the distribution, pressure and temperature of atmospheric gases, including water vapour, the propagation through the ionosphere is mainly affected by the number of free electrons along the signal path. Here, we present the use of dense regional GPS networks for extracting tropospheric zenith delays and ionospheric total electron content (TEC) maps in order to reduce the noise levels in InSAR images. The results show significant reduction in the root mean square (RMS) values when simultaneously combining the two corrections, both at short time periods where no surface deformation is expected, and at longer periods, where imaging of localized subsidence and fault creep is enhanced.
    Keywords: Gravity, Geodesy and Tides
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    Correction of inconsistencies in ECMWF's operational analysis data during de-aliasing of GRACE gravity models (2015)
    Oxford University Press
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    Publication Date: 2015-07-30
    Description: The main objective of the Gravity Recovery and Climate Experiment (GRACE) Atmospheric and Oceanic De-Aliasing Level-1B product (AOD1B) is the removal of high-frequency non-tidal mass variations due to sub-monthly mass transport in the atmosphere and oceans. Application of AOD1B shall avoid aliasing of these high-frequency signals into monthly gravity models derived from modern gravity missions and shall help to derive consistent orbit solutions for altimetry and Satellite Laser Ranging missions. The AOD1B 6-h series of spherical harmonic coefficients up to degree and order 100 are routinely generated at the German Research Centre for Geoscience and distributed to the GRACE Science Data System and the user community. Inputs for this product are acquired from numerical weather prediction models which are regularly revised and consequently not stable in time. The latest AOD1B release 5 (RL05) is based, as all other releases, on input from ECMWF and does not resolve this problem of discontinuities present in the surface pressure and surface geopotential input data. This might contaminate the gravity field variations derived from atmospheric mass variations. In this paper we present a method to overcome this problem during future AOD1B product generation, as well as two new Level-2 products (GAE and GAF) that, over land, fix a posteriori the two jumps present in the already distributed Level-2 RL05 monthly gravity models which were based on AOD1B RL05. The impact of the proposed correction on the variations and long-term trend of the total mass of the atmosphere and on the ice mass balance over Antarctica and over Greenland is also illustrated. We found that the GAE/GAF-corrected trend of the global atmospheric mass over the GRACE mission lifetime significantly decreased from –0.05 to –0.02 mm yr –1 in terms of geoid height. A considerable effect (33 per cent) was also found in the quadratic term of ice mass loss over Antarctica which results in an acceleration of 3.2 Gt yr –1  yr –1 smaller than without applying this correction.
    Keywords: Gravity, Geodesy and Tides
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    Did glacially induced TPW end the ice age? A reanalysis (2015)
    Oxford University Press
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    Publication Date: 2015-07-17
    Description: Previous studies of Earth rotation perturbations due to ice-age loading have predicted a slow secular drift of the rotation axis relative to the surface geography (i.e. true polar wander, TPW) of order of several degrees over the Plio-Pleistocene. It has been argued that this drift and the change in the geographic distribution of solar insolation that it implies may have been responsible for important transitions in ice-age climate, including the termination of ice-age cycles.We use a revised rotational stability theory that incorporates a more accurate treatment of the Earth's background ellipticity to reconsider this issue, and demonstrate that the net displacement of the pole predicted in earlier studies disappears. This more muted polar motion is due to two factors: first, the revised theory no longer predicts the permanent shift in the rotation axis, or the so-called ‘unidirectional TPW’, that appears in the traditional stability theory; and, second, the increased background ellipticity incorporated in the revised predictions acts to reduce the normal mode amplitudes governing the motion of the pole. We conclude that ice-age-induced TPW was not responsible for the termination of the ice age. This does not preclude the possibility that TPW induced by mantle convective flow may have played a role in major Plio-Pleistocene climate transitions, including the onset of Northern Hemisphere glaciation.
    Keywords: Gravity, Geodesy and Tides
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    Spurious barometric pressure acceleration in Antarctica and propagation into GRACE Antarctic mass change estimates (2016)
    Oxford University Press
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    Publication Date: 2016-07-03
    Description: Apparent acceleration in Gravity Recovery and Climate Experiment (GRACE) Antarctic ice mass time-series may reflect both ice discharge and surface mass balance contributions. However, a recent study suggests there is also contamination from errors in atmospheric pressure de-aliasing fields [European Center for Medium-Range Weather Forecast (ECMWF) operational products] used during GRACE data processing. To further examine this question, we compare GRACE atmospheric pressure de-aliasing (GAA) fields with in situ surface pressure data from coastal and inland stations. Differences between the two are likely due to GAA errors, and provide a measure of error in GRACE solutions. Time-series of differences at individual weather stations are fit to four presumed error components: annual sinusoids, a linear trend, an acceleration term and jumps at times of known ECMWF model changes. Using data from inland stations, we estimate that atmospheric pressure error causes an acceleration error of about +7.0 Gt yr –2 , which is large relative to prior GRACE estimates of Antarctic ice mass acceleration in the range of –12 to –14 Gt yr –2 . We also estimate apparent acceleration rates from other barometric pressure (reanalysis) fields, including ERA-Interim, MERRA and NCEP/DOE. When integrated over East Antarctica, the four mass acceleration estimates (from GAA and the three reanalysis fields) vary considerably (by ~2–16 Gt yr –2 ). This shows the need for further effort to improve atmospheric mass estimates in this region of sparse in situ observations, in order to use GRACE observations to measure ice mass acceleration and related sea level change.
    Keywords: Gravity, Geodesy and Tides
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    Importance of far-field topographic and isostatic corrections for regional density modelling (2016)
    Oxford University Press
    Details
    Publication Date: 2016-08-27
    Description: The long-wavelength gravity field contains information about processes in the sublithospheric mantle. As satellite-derived gravity models now provide the long to medium-wavelength gravity field at unprecedented accuracy, techniques used to process gravity data need to be updated. We show that when determining these long-wavelengths, the treatment of topographic-isostatic effect (TIE) and isostatic effects (IE) is a likely source of error. We constructed a global isostatic model and calculated global TIE and IE. These calculations were done for ground stations as well as stations at satellite height. We considered both gravity and gravity gradients. Using these results, we determined how much of the gravity signal comes from distant sources. We find that a significant long-wavelength bias is introduced if far-field effects on the topographic effect are neglected. However, due to isostatic compensation far-field effects of the topographic effect are to a large degree compensated by the far-field IE. This means that far-field effects can be reduced effectively by always considering topographic masses together with their compensating isostatic masses. We show that to correctly represent the ultra-long wavelengths, a global background model should be used. This is demonstrated both globally and for a continental-scale case area in North America. In the case of regional modelling, where the ultra-long wavelengths are not of prime importance, gravity gradients can be used to help minimize correction errors caused by far-field effects.
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
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    Elastic tidal response of a laterally heterogeneous planet: a complete perturbation formulation (2016)
    Oxford University Press
    Details
    Publication Date: 2016-08-12
    Description: Constraining laterally varying structures in planetary interiors is important for understanding both the composition and the internal dynamics of a planet. Recognizing that seismic imaging technique is currently only viable for studying the Earth's interior structures, methods that can be supported by advanced space geodetic techniques may become alternatives to ‘image’ the interiors of other planets. The method of tidal tomography is one possibility, and it relies on high precision measurement of the response of a planet to its body tide. However, it is essential to develop an efficient analytical tool that computes the dependence of tidal response to 3-D interior structures. In this paper, we present a complete formulation of such an analytical tool, which calculates to high accuracy the tidal response of a terrestrial planet with lateral heterogeneities in its elastic and density structures. We treat the lateral heterogeneities as small perturbations and derive the governing equations based on the perturbation theory. In a spherical harmonic representation, equations at each order of perturbation are reduced into multiple matrix equations at harmonics that are allowed by mode couplings, and the total response equals the sum of all those single-harmonic responses, which can be solved semi-analytically. We test our perturbation method by applying it to the Moon with a harmonic degree-1 mantle structure for which the perturbation solutions of the tidal response are compared with those from a fully numerical method. The remarkable agreement between results from these two methods validates the perturbation method. As an example, we then use the perturbation method to evaluate the impact of lunar crustal thickness variations on tidal response of the Moon. We find that lunar crust produces much smaller degree-3 tidal responses than a relatively weak degree-1 structure in the deep lunar mantle. Our calculations show that degree-3 tidal response measurements may hold key constraints on possible degree-1 mantle structure of the Moon, as suggested from previous modelling results.
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
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    Generalized model for a Moho inversion from gravity and vertical gravity-gradient data (2016)
    Oxford University Press
    Details
    Publication Date: 2016-08-14
    Description: Seismic data are primarily used in studies of the Earth's lithospheric structure including the Moho geometry. In regions, where seismic data are sparse or completely absent, gravimetric or combined gravimetric-seismic methods could be applied to determine the Moho depth. In this study, we derive and present generalized expressions for solving the Vening Meinesz–Moritz's (VMM) inverse problem of isostasy for a Moho depth determination from gravity and vertical gravity-gradient data. By solving the (non-linear) Fredholm's integral equation of the first kind, the linearized observation equations, which functionally relate the (given) gravity/gravity-gradient data to the (unknown) Moho depth, are derived in the spectral domain. The VMM gravimetric results are validated by using available seismic and gravimetric Moho models. Our results show that the VMM Moho solutions obtained by solving the VMM problem for gravity and gravity-gradient data are almost the same. This finding indicates that in global applications, using the global gravity/gravity-gradient data coverage, the spherical harmonic expressions for the gravimetric forward and inverse modelling yield (theoretically) the same results. Globally, these gravimetric solutions have also a relatively good agreement with the CRUST1.0 and GEMMA GOCE models in terms of their rms Moho differences (4.7 km and 4.1 km, respectively).
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
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    Topics: Geosciences
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    Investigating hydrological contributions to volcano monitoring signals: a time-lapse gravity example (2016)
    Oxford University Press
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    Publication Date: 2016-08-27
    Description: Geophysical techniques are widely used to monitor volcanic unrest. A number of studies have also demonstrated that hydrological processes can produce or trigger geophysical signals. Hydrologically induced gravity signals have previously been recorded by specifically designed gravity surveys as well as, inadvertently, by volcano monitoring studies. Water table corrections of microgravity surveys are commonplace. However, the fluctuations of the water table beneath survey locations are often poorly known, and such a correction fails to account for changes in water-mass storage in the unsaturated zone. Here, we combine 2-D axis-symmetrical numerical fluid-flow models with an axis-symmetric, distributed-mass, gravity calculation to model gravity changes in response to fluctuating hydrological recharge. Flow simulations are based on tropical volcanic settings where high surface permeabilities promote thick unsaturated zones. Our study highlights that mass storage (saturation) changes within the unsaturated zone beneath a survey point can generate recordable gravity changes. We show that for a tropical climate, recharge variations can generate gravity variations of over 150 μGal; although, we demonstrate that for the scenarios investigated here, the probability of recording such large signals is low. Our modelling results indicate that microgravity survey corrections based on water table elevation may result in errors of up to 100 μGal. The effect of inter-annual recharge fluctuations dominate over seasonal cycles which makes prediction and correction of the hydrological contribution more difficult. Spatial hydrogeological heterogeneity can also impact on the accuracy of relative gravity surveys, and can even result in the introduction of additional survey errors. The loading fluctuations associated with saturation variations in the unsaturated zone may also have implications for other geophysical monitoring techniques, such as geodetic monitoring of ground deformation.
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
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    Topics: Geosciences
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    GRACE time-variable gravity field recovery using an improved energy balance approach (2015)
    Oxford University Press
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    Publication Date: 2015-10-25
    Description: A new approach based on energy conservation principle for satellite gravimetry mission has been developed and yields more accurate estimation of in situ geopotential difference observables using K-band ranging (KBR) measurements from the Gravity Recovery and Climate Experiment (GRACE) twin-satellite mission. This new approach preserves more gravity information sensed by KBR range-rate measurements and reduces orbit error as compared to previous energy balance methods. Results from analysis of 11 yr of GRACE data indicated that the resulting geopotential difference estimates agree well with predicted values from official Level 2 solutions: with much higher correlation at 0.9, as compared to 0.5–0.8 reported by previous published energy balance studies. We demonstrate that our approach produced a comparable time-variable gravity solution with the Level 2 solutions. The regional GRACE temporal gravity solutions over Greenland reveals that a substantially higher temporal resolution is achievable at 10-d sampling as compared to the official monthly solutions, but without the compromise of spatial resolution, nor the need to use regularization or post-processing.
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
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    Monte Carlo simulation for background study of geophysical inspection with cosmic-ray muons (2016)
    Oxford University Press
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    Publication Date: 2016-06-19
    Description: Several attempts have been made to obtain a radiographic image inside volcanoes using cosmic-ray muons (muography). Muography is expected to resolve highly heterogeneous density profiles near the surface of volcanoes. However, several prior works have failed to make clear observations due to contamination by background noise. The background contamination leads to an overestimation of the muon flux and consequently a significant underestimation of the density in the target mountains. To investigate the origin of the background noise, we performed a Monte Carlo simulation. The main components of the background noise in muography are found to be low-energy protons, electrons and muons in case of detectors without particle identification and with energy thresholds below 1 GeV. This result was confirmed by comparisons with actual observations of nuclear emulsions. This result will be useful for detector design in future works, and in addition some previous works of muography should be reviewed from the view point of background contamination.
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
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    Topics: Geosciences
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    Estimating the sea level highstand during the last interglacial: a probabilistic massive ensemble approach (2016)
    Oxford University Press
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    Publication Date: 2016-06-09
    Description: Essential to understanding sea level change and its causes during the last interglacial (LIG) is the quantification of uncertainties. In order to estimate the uncertainties, we develop a statistical framework for the comparison of palaeoclimatic sea level index points and GIA model predictions. For the investigation of uncertainties, as well as to generate better model predictions, we implement a massive ensemble approach by applying a data assimilation scheme based on particle filter methods. The different runs are distinguished through varying ice sheet reconstructions based on oxygen-isotope curves and different parameter selections within the GIA model. This framework has several advantages over earlier work, such as the ability to examine either the contribution of individual observations to the results or the probability of specific input parameters. This exploration of input parameters and data leads to a larger range of estimates than previously published work. We illustrate how the assumptions that enter into the statistical analysis, such as the existence of outliers in the observational database or the initial ice volume history, can introduce large variations to the estimate of the maximum highstand. Thus, caution is required to avoid overinterpreting results. We conclude that there are reasonable doubts whether the data sets previously used in statistical analyses are able to tightly constrain the value of maximum highstand during the LIG.
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
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    Topics: Geosciences
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    An isostatic study of the Karoo basin and underlying lithosphere in 3-D (2016)
    Oxford University Press
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    Publication Date: 2016-06-01
    Description: A 3-D density model of the crust and upper mantle beneath the Karoo basin is presented here. The model is constrained using potential field, borehole and seismic data. Uplift of the basin by the end of the Cretaceous has resulted in an unusually high plateau (〉1000 m) covering a large portion of South Africa. Isostatic studies show the topography is largely compensated by changes in Moho depths (~35 km on-craton and 〉45 km off-craton) and changes in lithospheric mantle densities between the Kaapvaal Craton and surrounding regions (~50 kg m –3 increase from on- to off-craton). This density contrast is determined by inverted satellite gravity and gravity gradient data. The highest topography along the edge of the plateau (〉1200 m) and a strong Bouguer gravity low over Lesotho, however, can only be explained by a buoyant asthenosphere with a density decrease of around 40 kg m –3 .
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
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    Topics: Geosciences
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    Rotation change in the orientation of the centre-of-figure frame caused by large earthquakes (2016)
    Oxford University Press
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    Publication Date: 2016-06-19
    Description: A method to estimate the rotation change in the orientation of the centre-of-figure (CF) frame caused by earthquakes is proposed for the first time. This method involves using the point dislocation theory based on a spherical, non-rotating, perfectly elastic and isotropic (SNREI) Earth. The rotation change in the orientation is related solely to the toroidal displacements of degree one induced by the vertical dip slip dislocation, and the spheroidal displacements induced by an earthquake have no contribution. The effects of two recent large earthquakes, the 2004 Sumatra and the 2011 Tohoku-Oki, are studied. Results showed that the Sumatra and Tohoku-Oki earthquakes both caused the CF frame to rotate by at least tens of μas (micro-arc-second). Although the visible co-seismic displacements are identified and removed from the coordinate time-series, the rotation change due to the unidentified ones and errors in removal is non-negligible. Therefore, the rotation change in the orientation of the CF frame due to seismic deformation should be taken into account in the future in reference frame and geodesy applications.
    Keywords: Gravity, Geodesy and Tides
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    Topics: Geosciences
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    Formulation of geopotential difference determination using optical-atomic clocks onboard satellites and on ground based on Doppler cancellation system (2016)
    Oxford University Press
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    Publication Date: 2016-06-25
    Description: In this study, we propose an approach for determining the geopotential difference using high-frequency-stability microwave links between satellite and ground station based on Doppler cancellation system. Suppose a satellite and a ground station are equipped with precise optical-atomic clocks (OACs) and oscillators. The ground oscillator emits a signal with frequency f a towards the satellite and the satellite receiver (connected with the satellite oscillator) receives this signal with frequency f b which contains the gravitational frequency shift effect and other signals and noises. After receiving this signal, the satellite oscillator transmits and emits, respectively, two signals with frequencies f b and f c towards the ground station. Via Doppler cancellation technique, the geopotential difference between the satellite and the ground station can be determined based on gravitational frequency shift equation by a combination of these three frequencies. For arbitrary two stations on ground, based on similar procedures as described above, we may determine the geopotential difference between these two stations via a satellite. Our analysis shows that the accuracy can reach 1 m 2 s – 2 based on the clocks’ inaccuracy of about 10 –17 (s s –1 ) level. Since OACs with instability around 10 –18 in several hours and inaccuracy around 10 –18 level have been generated in laboratory, the proposed approach may have prospective applications in geoscience, and especially, based on this approach a unified world height system could be realized with one-centimetre level accuracy in the near future.
    Keywords: Gravity, Geodesy and Tides
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    Topics: Geosciences
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    Depth distribution of the sedimentary basin and Moho undulation in the Yellow Sea, NE Asia interpreted by using satellite-derived gravity field (2015)
    Oxford University Press
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    Publication Date: 2015-04-24
    Description: We interpreted the TRIDENT satellite derived gravity field to provide detailed insights into the spatial distribution of the crustal density structures in the area of the Yellow Sea. We used 3-D forward density modelling for the interpretation that incorporated constraints from existing geological and geophysical information. A gravity stripping method is used to separate out the gravity effects of different geological crustal structures. From this analysis we see that (1) the Gunsan sedimentary basin is isostatically compensated. (2) The satellite-derived Bouguer anomalies ranging from 15 to –30 x 10 –5 m s –2 are linked to basin thicknesses in the Yellow Sea. (3) The calculated Moho depth in the Yellow Sea varies from 27 km beneath the deep sedimentary basin to 34 km in the uplifted zones. (4) Moho depth calculations show two distinct areas, characterized by the deepest Moho depths and the largest crustal thicknesses in the Yellow Sea. The one region extends along the Qianliyan Uplift Zone from Jiaodong to Hongsung while the other area extends from southeastern China to Hongsung in the Korean peninsula. Compared to previous works we suggest that they are the part of the collisions zone between North and South China Blocks extending from China to the Korean peninsula via the Yellow Sea.
    Keywords: Gravity, Geodesy and Tides
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    On the regularization of regional gravity field solutions in spherical radial base functions (2015)
    Oxford University Press
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    Publication Date: 2015-06-19
    Description: Regional refinement of the gravity field models from satellite data using spherical radial base functions (SRBF) is an ill-posed problem. This is mainly due to the regional confinement of the data and the base functions, which leads to severe instabilities in the solutions. Here, this ill-posedness as well as the related regularization process are investigated. We compare three methods for the choice of the regularization parameter, which have been frequently used in gravity modelling. These methods are (1) the variance component estimation (VCE), (2) the generalized cross validation (GCV) and (3) the L-curve criterion. A particular emphasis is put on the impact of the SRBF type on the regularization parameter. To do this, we include two types of SRBF which are often used for regional gravity field modelling. These are the Shannon SRBF or the reproducing kernel and the Spline SRBF. The investigations are performed on two months of the real GOCE ultrasensitive gravity gradients over Central Africa and Amazon. The solutions are validated against a state-of-the-art global gravity solution. We conclude that if a proper regularization method is applied, both SRBF deliver more or less the same accuracy. We show that when the Shannon wavelet is used, the L-curve method gives the best results, while with the Spline kernel, the GCV outperforms the other two methods. Moreover, we observe that the estimated coefficients for the Spline kernel cannot be spatially interpreted. In contrast, the coefficients obtained for the Shannon wavelet reflect the energy of the recovered gravity field with a correlation factor of above 95 per cent. Therefore, when combined with the L-curve method, the Shannon SRBF is advantageous for regional gravity field estimation, since it is one of the simplest band-limited SRBF. In addition, it delivers promising solutions and the estimated coefficients represent the characteristics of the gravity field within the target region.
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
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    Topics: Geosciences
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    A modified acceleration-based monthly gravity field solution from GRACE data (2015)
    Oxford University Press
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    Publication Date: 2015-06-28
    Description: This paper describes an alternative acceleration approach for determining GRACE monthly gravity field models. The main differences compared to the traditional acceleration approach can be summarized as: (1) The position errors of GRACE orbits in the functional model are taken into account; (2) The range ambiguity is eliminated via the difference of the range measurements and (3) The mean acceleration equation is formed based on Cowell integration. Using this developed approach, a new time-series of GRACE monthly solution spanning the period January 2003 to December 2010, called Tongji_Acc RL01, has been derived. The annual signals from the Tongji_Acc RL01 time-series agree well with those from the GLDAS model. The performance of Tongji_Acc RL01 shows that this new model is comparable with the RL05 models released by CSR and JPL as well as with the RL05a model released by GFZ.
    Keywords: Gravity, Geodesy and Tides
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    A new bound constraints method for 3-D potential field data inversion using Lagrangian multipliers (2015)
    Oxford University Press
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    Publication Date: 2015-02-19
    Description: In this paper, we present a method for incorporating prior geological information into potential field data inversion problem. As opposed to the traditional inverse algorithm, our proposed method takes full advantage of prior geological information as a constraint and thus obtains a new objective function for inversion by adding Lagrangian multipliers and slack variables to the traditional inversion method. These additional parameters can be easily solved during iterations. We used both synthetic and observed data sets to test the stability and validity of the proposed method. Our results using synthetic gravity data show that our new method predicts depth and density anomalies more efficiently and accurately than the traditional inversion method that does not include prior geological constraints. Then using observed gravity data in the Three Gorges area and geological constraint information, we obtained the density distribution of the upper and middle crust in this area thus revealing its geological structure. These results confirm the proposed method's validity and indicate its potential application for magnetism data inversion and exploration of geological structures.
    Keywords: Gravity, Geodesy and Tides
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    Recurrent slow slip event reveals the interaction with seismic slow earthquakes and disruption from large earthquake (2015)
    Oxford University Press
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    Publication Date: 2015-07-10
    Description: It remains enigmatic how slow slip events (SSEs) interact with other slow seismic events and large distant earthquakes at many subduction zones. Here we model the spatiotemporal slip evolution of the most recent long-term SSE in 2009–2011 in the Bungo Channel region, southwest Japan using GEONET GPS position time-series and a Kalman filter-based, time-dependent slip inversion method. We examine the space-time relationship between the geodetically determined slow slip transient and seismically observed low frequency earthquakes (LFEs) and very-low frequency earthquakes (V-LFEs) near the Nankai trough. We find a strong but distinct temporal correlation between transient slip and LFEs and V-LFEs, suggesting a different relationship to the SSE. We also find the great Tohoku-Oki earthquake appears to disrupt the normal source process of the SSE, probably reflecting large-scale stress redistribution caused by the earthquake. Comparison of the 2009–2011 SSE with others in the same region shows much similarity in slip and moment release, confirming its recurrent nature. Comparison of transient slip with plate coupling shows that slip transients mainly concentrate on the transition zone from strong coupling region to downdip LFEs with transient slip relieving elastic strain accumulation at transitional depth. The less consistent spatial correlation between the long-term SSE and seismic slow earthquakes, and susceptibility of these slow earthquakes to various triggering sources including long-term slow slip, suggests caution in using the seismically determined slow earthquakes as a proxy for slow slip.
    Keywords: Gravity, Geodesy and Tides
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    A normal mode treatment of semi-diurnal body tides on an aspherical, rotating and anelastic Earth (2015)
    Oxford University Press
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    Publication Date: 2015-07-04
    Description: Normal mode treatments of the Earth's body tide response were developed in the 1980s to account for the effects of Earth rotation, ellipticity, anelasticity and resonant excitation within the diurnal band. Recent space-geodetic measurements of the Earth's crustal displacement in response to luni-solar tidal forcings have revealed geographical variations that are indicative of aspherical deep mantle structure, thus providing a novel data set for constraining deep mantle elastic and density structure. In light of this, we make use of advances in seismic free oscillation literature to develop a new, generalized normal mode theory for the tidal response within the semi-diurnal and long-period tidal band. Our theory involves a perturbation method that permits an efficient calculation of the impact of aspherical structure on the tidal response. In addition, we introduce a normal mode treatment of anelasticity that is distinct from both earlier work in body tides and the approach adopted in free oscillation seismology. We present several simple numerical applications of the new theory. First, we compute the tidal response of a spherically symmetric, non-rotating, elastic and isotropic Earth model and demonstrate that our predictions match those based on standard Love number theory. Second, we compute perturbations to this response associated with mantle anelasticity and demonstrate that the usual set of seismic modes adopted for this purpose must be augmented by a family of relaxation modes to accurately capture the full effect of anelasticity on the body tide response. Finally, we explore aspherical effects including rotation and we benchmark results from several illustrative case studies of aspherical Earth structure against independent finite-volume numerical calculations of the semi-diurnal body tide response. These tests confirm the accuracy of the normal mode methodology to at least the level of numerical error in the finite-volume predictions. They also demonstrate that full coupling of normal modes, rather than group coupling, is necessary for accurate predictions of the body tide response.
    Keywords: Gravity, Geodesy and Tides
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    Fault locking near Istanbul: indication of earthquake potential from InSAR and GPS observations (2016)
    Oxford University Press
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    Publication Date: 2016-02-26
    Description: A sequence of large earthquakes occurred along the North Anatolian fault in the 20th century. These earthquakes, including the 1999 Izmit/Düzce earthquakes, generally propagated westward towards the Marmara Sea, defining the Main Marmara fault as a potential seismic gap. It is important to conduct a detailed assessment of the seismic hazards along the main Marmara fault because the megacity Istanbul lies only approximately 10 km north of the eastern segment of the Main Marmara fault, which is referred to as the Princes’ Islands Fault segment (PIF). Here, we study the locking status of this fault segment to evaluate the seismic hazard potential. For the first time, combined ascending and descending Interferometric Synthetic Aperture Radar and Global Positioning System observations were used to investigate the crustal deformation associated with the PIF. After careful corrections of the estimated ground velocity, a deformation pattern relating to fault locking near the Princes’ Islands was identified. The modeling results revealed that the slip rate and locking depth of the fault segment show a clear trade-off, which were estimated as 18.9 ± 7.2 mm yr –1 and 12.1 ± 7.0 km, respectively. With a moment accumulation rate of 1.7 ± 0.4  x  10 17 Nm yr –1 (proportional to the product of slip rate and locking depth), our results imply a build-up of a geodetic moment on the PIF and therefore a potential for earthquake hazards in the vicinity of the Istanbul megacity.
    Keywords: Gravity, Geodesy and Tides
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    An improved geodetic source model for the 1999 Mw 6.3 Chamoli earthquake, India (2016)
    Oxford University Press
    Details
    Publication Date: 2016-02-20
    Description: We present a distributed slip model for the 1999 M w 6.3 Chamoli earthquake of north India using interferometric synthetic aperture radar (InSAR) data from both ascending and descending orbits and Bayesian estimation of confidence levels and trade-offs of the model geometry parameters. The results of fault-slip inversion in an elastic half-space show that the earthquake ruptured a $9 _{ - 2.2}^{\circ + 3.4}$ northeast-dipping plane with a maximum slip of ~1 m. The fault plane is located at a depth of ~ $15.9_{ - 3.0}^{ + 1.1}$ km and is ~120 km north of the Main Frontal Thrust, implying that the rupture plane was on the northernmost detachment near the mid-crustal ramp of the Main Himalayan Thrust. The InSAR-determined moment is 3.35 x 10 18 Nm with a shear modulus of 30 GPa, equivalent to M w 6.3, which is smaller than the seismic moment estimates of M w 6.4–6.6. Possible reasons for this discrepancy include the trade-off between moment and depth, uncertainties in seismic moment tensor components for shallow dip-slip earthquakes and the role of earth structure models in the inversions. The released seismic energy from recent earthquakes in the Garhwal region is far less than the accumulated strain energy since the 1803 M s 7.5 earthquake, implying substantial hazard of future great earthquakes.
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
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    3-D linear inversion of gravity data: method and application to Basse-Terre volcanic island, Guadeloupe, Lesser Antilles (2016)
    Oxford University Press
    Details
    Publication Date: 2016-03-02
    Description: We use a Bayesian formalism combined with a grid node discretization for the linear inversion of gravimetric data in terms of 3-D density distribution. The forward modelling and the inversion method are derived from seismological inversion techniques in order to facilitate joint inversion or interpretation of density and seismic velocity models. The Bayesian formulation introduces covariance matrices on model parameters to regularize the ill-posed problem and reduce the non-uniqueness of the solution. This formalism favours smooth solutions and allows us to specify a spatial correlation length and to perform inversions at multiple scales. We also extract resolution parameters from the resolution matrix to discuss how well our density models are resolved. This method is applied to the inversion of data from the volcanic island of Basse-Terre in Guadeloupe, Lesser Antilles. A series of synthetic tests are performed to investigate advantages and limitations of the methodology in this context. This study results in the first 3-D density models of the island of Basse-Terre for which we identify: (i) a southward decrease of densities parallel to the migration of volcanic activity within the island, (ii) three dense anomalies beneath Petite Plaine Valley, Beaugendre Valley and the Grande-Découverte-Carmichaël-Soufrière Complex that may reflect the trace of former major volcanic feeding systems, (iii) shallow low-density anomalies in the southern part of Basse-Terre, especially around La Soufrière active volcano, Piton de Bouillante edifice and along the western coast, reflecting the presence of hydrothermal systems and fractured and altered rocks.
    Keywords: Gravity, Geodesy and Tides
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    Topics: Geosciences
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    Estimation of the gravimetric pole tide by stacking long time-series of GGP superconducting gravimeters (2016)
    Oxford University Press
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    Publication Date: 2016-02-20
    Description: We compute the gravimetric factor at the Chandler wobble (CW) frequency using time-series from superconducting gravimeters (SG) longer than a decade. We first individually process the polar motion and data at each individual gravity station to estimate the gravimetric factor amplitude and phase, then we make a global analysis by applying a stacking method to different subsets of up to seven SG stations. The stacking is an efficient way of getting rid of local effects and improving the signal-to-noise ratio of the combined data sets. Using the stacking method, we find a gravimetric factor amplitude and phase of 1.118 ± 0.016 and –0.45 ± 0.66 deg, respectively, which is smaller in amplitude than expected. The sources of error are then carefully considered. For both local and global analyses, the uncertainties on our results are reliably constrained by computing the standard deviation of the estimates of the gravimetric factor amplitude and phase for increasing length of the time-series. Constraints on the CW anelastic dissipation can be set since any departure of the gravimetric factor from its elastic value may provide some insights into the dissipative processes that occur at the CW period. In particular, assuming given rheological models for the Earth's mantle enables us to make the link between the gravimetric factor phase and the CW quality factor.
    Keywords: Gravity, Geodesy and Tides
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    Temporal variation of tidal parameters in superconducting gravimeter time-series (2016)
    Oxford University Press
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    Publication Date: 2016-02-21
    Description: Analysing independent 1-yr data sets of 10 European superconducting gravimeters (SG) reveals statistically significant temporal variations of M2 tidal parameters. Both common short-term (〈2 yr) and long-term (〉2 yr) features are identified in all SG time-series but one. The averaged variations of the amplitude factor are about 0.2. The path of load vector variations equivalent to the temporal changes of tidal parameters suggests the presence of an 8.85 yr modulation (lunar perigee). The tidal waves having the potential to modulate M2 with this period belong to the 3rd degree constituents. Their amplitude factors turn out to be much closer to body tide model predictions than that of the main 2nd degree M2, which indicates ocean loading for 3rd degree waves to be less prominent than for 2nd degree waves within the M2 group. These two different responses to the loading suggest that the observed modulation is more due to insufficient frequency resolution of limited time-series rather than to time variable loading. Presently, SG gravity time-series are still too short to prove if time variable loading processes are involved too as in case of the annual M2 modulation known to appear for analysis intervals of less than 1 yr. Whatever the variations are caused by, they provide the upper accuracy limit for earth model validation and permit estimating the temporal stability of SG scale factors and assessing the quality of gravity time-series.
    Keywords: Gravity, Geodesy and Tides
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    Fault locking near Istanbul: indication of earthquake potential from InSAR and GPS observations (2016)
    Oxford University Press
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    Publication Date: 2016-02-27
    Description: A sequence of large earthquakes occurred along the North Anatolian fault in the 20th century. These earthquakes, including the 1999 Izmit/Düzce earthquakes, generally propagated westward towards the Marmara Sea, defining the Main Marmara fault as a potential seismic gap. It is important to conduct a detailed assessment of the seismic hazards along the main Marmara fault because the megacity Istanbul lies only approximately 10 km north of the eastern segment of the Main Marmara fault, which is referred to as the Princes’ Islands Fault segment (PIF). Here, we study the locking status of this fault segment to evaluate the seismic hazard potential. For the first time, combined ascending and descending Interferometric Synthetic Aperture Radar and Global Positioning System observations were used to investigate the crustal deformation associated with the PIF. After careful corrections of the estimated ground velocity, a deformation pattern relating to fault locking near the Princes’ Islands was identified. The modeling results revealed that the slip rate and locking depth of the fault segment show a clear trade-off, which were estimated as 18.9 ± 7.2 mm yr –1 and 12.1 ± 7.0 km, respectively. With a moment accumulation rate of 1.7 ± 0.4  x  10 17 Nm yr –1 (proportional to the product of slip rate and locking depth), our results imply a build-up of a geodetic moment on the PIF and therefore a potential for earthquake hazards in the vicinity of the Istanbul megacity.
    Keywords: Gravity, Geodesy and Tides
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    Coloured noise effects on deformation parameters of permanent GPS networks (2016)
    Oxford University Press
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    Publication Date: 2016-02-06
    Description: Deformation analysis in general and strain analysis in particular using permanent GPS networks require proper analysis of time-series in which all functional effects are taken into consideration and all stochastic effects are captured using an appropriate noise model. This contribution addresses both issues when considering the strain parameters of a GPS network. Estimates of spatial correlation, time correlated noise, and multivariate power spectrum for daily position time-series of the Southern California Integrated GPS Network (SCIGN) stations collected between 1996 and 2011 are obtained. Significant signals with periods of 13.63 d and those related to the GPS draconitic year are identified in these time-series. We aim to assess the effect of a realistic noise model of the series on the uncertainties of the strain parameters including displacements, normal and shear strains, and rotations. For the SCIGN network considered, the following results are highlighted. Contrary to the common belief, the uncertainties of the displacements parameters become smaller when taking a realistic noise model into account. This however was not the case when assessing the noise characteristics of the normal and shear strain, and rotation parameters. The uncertainties increase nearly by a factor of two, in agreement to what is expected. Some of the significant deformation parameters of the white noise model become less significant in case of the realistic noise model.
    Keywords: Gravity, Geodesy and Tides
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    Crustal vertical deformation response to different spatial scales of GRACE and GCMs surface loading (2015)
    Oxford University Press
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    Publication Date: 2015-11-27
    Description: Crustal vertical deformation (CVD) observed by continuous GPS height time-series can be explained largely by surface loading effects recovered from both Gravity Recover and Climate Experiment (GRACE) and General Circulation Models (GCMs) data. We first show that lower degree CVD spatial spectrum due to the Earth's elastic response to a uniform surface loading plays more important roles than that of high-degree case. We then demonstrate that GRACE data with 300–400 km spatial resolution have the ability to detect 99 per cent power of global and regional CVD in spatial spectrum domain using a global frequency–wavenumber spectrum method. We can just use either GRACE or GCMs 36 degree/order (d/o) spherical harmonic coefficients (SHCs) which correspond to 500 km spatial resolution to acquire more than 90 per cent variance of total CVD modeled by up to 180 d/o SHCs at 98 per cent global gridpoints. Globally, CVD modeled by GRACE loading can explain 72 per cent annual amplitude and 69 per cent variance of GPS observed height time-series, which is better than the GCMs results of 64 per cent for annual amplitude and 41 per cent for variance. Using a three cornered hat method, we also show that the noise level of monthly averaged CVD is about 3 mm for both GPS height time-series and GRACE loading result, while that of GCMs result is only 1.3 mm.
    Keywords: Gravity, Geodesy and Tides
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    Derivation of 3-D surface deformation from an integration of InSAR and GNSS measurements based on Akaike's Bayesian Information Criterion (2015)
    Oxford University Press
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    Publication Date: 2015-11-25
    Description: We present a new method to derive 3-D surface deformation from an integration of interferometric synthetic aperture radar (InSAR) images and Global Navigation Satellite System (GNSS) observations based on Akaike's Bayesian Information Criterion (ABIC), considering relationship between deformations of neighbouring locations. This method avoids interpolated errors by excluding the interpolation of GNSS into the same spatial resolution as InSAR images and harnesses the data sets and the prior smooth constraints of surface deformation objectively and simultaneously by using ABIC, which were inherently unresolved in previous studies. In particular, we define surface roughness measuring smoothing degree to evaluate the performance of the prior constraints and deduce the formula of the covariance for the estimation errors to estimate the uncertainty of modelled solution. We validate this method using synthetic tests and the 2008 M w 7.9 Wenchuan earthquake. We find that the optimal weights associated with ABIC minimum are generally at trade-off locations that balance contributions from InSAR, GNSS data sets and the prior constraints. We use this method to evaluate the influence of the interpolated errors from the Ordinary Kriging algorithm on the derivation of surface deformation. Tests show that the interpolated errors may contribute to biasing very large weights imposed on Kriged GNSS data, suggesting that fixing the relative weights is required in this case. We also make a comparison with SISTEM method, indicating that our method allows obtaining better estimations even with sparse GNSS observations. In addition, this method can be generalized to provide a solution for situations where some types of data sets are lacking and can be exploited further to account for data sets such as the integration of displacements along radar lines and offsets along satellite tracks.
    Keywords: Gravity, Geodesy and Tides
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    Impacts of GNSS position offsets on global frame stability (2015)
    Oxford University Press
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    Publication Date: 2015-11-27
    Description: While it has been known for some time that offsets in the time-series of Global Navigation Satellite System (GNSS) position estimates degrade station velocity determinations, the magnitude of the effect has not been clear. Using products of the International GNSS Service (IGS), we assess the impact empirically by injecting progressively larger numbers of artificial offsets and solving for a series of long-term secular GNSS frames. Our results show that the stability of the IGS global frame datum is fairly robust, with significant effects at the formal error level only for the R x (and Y-pole) and R z rotational orientations. On the other hand, station velocity estimates are more seriously affected, especially the vertical component. For the typical IGS station, the mean vertical rate uncertainty is already limited to 0.34 mm yr –1 for the current set of position discontinuities. If the number of breaks doubles, which might occur using newer detection schemes, then that uncertainty will worsen by ~40 per cent to 0.48 mm yr –1 . This error source is generally a more important component of realistic velocity uncertainties than any other, including accounting for temporal correlations in the GNSS data. The only way to improve future GNSS velocity estimates is to severely limit manmade displacements at the tracking stations.
    Keywords: Gravity, Geodesy and Tides
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    Impact of Atmospheric and Oceanic De-aliasing Level-1B (AOD1B) products on precise orbits of altimetry satellites and altimetry results (2016)
    Oxford University Press
    Details
    Publication Date: 2016-02-03
    Description: We have extended backwards from 2001 to 1979 the current release 05 (RL05) of the Gravity Recovery and Climate Experiment (GRACE) Atmospheric and Oceanic De-aliasing Level-1B (AOD1B) product and studied the impact of this and a previous release 04 (RL04) of the AOD1B product on precise orbits of five altimetry satellites (ERS-1, ERS-2, TOPEX/Poseidon, Envisat and Jason-1) for the time span 1991–2012, as compared to the case when no AOD1B product is used. We have found that using AOD1B RL05 product reduces root mean square (RMS) fits of satellite laser ranging (SLR) observations by about 1.0–6.4 per cent, 2-d arc overlaps in radial, cross-track and along-track directions by about 1.3–12.0, 0.3–10.0 and 2.0–10.0 per cent, respectively, for various satellites tested, as compared to the case without AOD1B product. Using AOD1B RL05 product instead of RL04 one reduces SLR RMS fits by 0.1–0.7 per cent, 2-d arc overlaps in radial, cross-track and along-track directions by 0.1–0.6, 0.1–1.3 and 0.2–1.2 per cent, respectively, for the satellite orbits tested. The multi-mission crossover analysis shows that the application of an AOD1B product reduces the scatter of radial errors by 0.4–2.8 per cent for the satellite missions studied. At the regions with the most pronounced changes the use of the AOD1B products improves the consistency between the sea level as measured by the TOPEX and ERS-2 missions and by the Jason-1 and Envisat missions by 5 to 10 per cent (globally by about 2 per cent). The results of our study show that extended AOD1B RL05 product performs better than the AOD1B RL04 and improves orbits of altimetry satellites and consistency of sea level products.
    Keywords: Gravity, Geodesy and Tides
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    Comment on: 'The quest for a consistent signal in ground and GRACE gravity time-series', by Michel Van Camp, Olivier de Viron, Laurent Metivier, Bruno Meurers and Olivier Francis (2014)
    Oxford University Press
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    Publication Date: 2014-10-23
    Description: The paper in question by Van Camp and co-authors [MVC] challenges previous work showing that ground gravity data arising from hydrology can provide a consistent signal for the comparison with satellite gravity data. The data sets used are similar to those used previously, that is, the gravity field as measured by the GRACE satellites versus ground-based data from superconducting gravimeters (SGs) over the same continental area, in this case Central Europe. One of the main impediments in this paper is the presentation that is frequently confusing and misleading as to what the data analysis really shows, for example, the irregular treatment of annual components that are first subtracted then reappear in the analysis. More importantly, we disagree on specific points. Two calculations are included in our comment to illustrate where we believe that the processing in [MVC] paper is deficient. The first deals with their erroneous treatment of the global hydrology using a truncated spherical harmonic approach which explains almost a factor 2 error in their computation of the loading. The second shows the effect of making the wrong assumption in the GRACE/hydrology/surface gravity comparison by inverting the whole of the hydrology loading for underground stations. We also challenge their claims that empirical orthogonal function techniques cannot be done in the presence of periodic components, and that SG data cannot be corrected for comparisons with GRACE data. The main conclusion of their paper, that there is little coherence between ground gravity stations and this invalidates GRACE comparisons, is therefore questionable. There is nothing in [MVC] that contradicts any of the previous papers that have shown clearly a strong relation between seasonal signals obtained from both ground gravity and GRACE satellite data.
    Keywords: Gravity, Geodesy and Tides
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    The rotational feedback on linear-momentum balance in glacial isostatic adjustment (2014)
    Oxford University Press
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    Publication Date: 2014-10-23
    Description: The influence of changes in surface ice-mass redistribution and associated viscoelastic response of the Earth, known as glacial isostatic adjustment (GIA), on the Earth's rotational dynamics has long been known. Equally important is the effect of the changes in the rotational dynamics on the viscoelastic deformation of the Earth. This signal, known as the rotational feedback, or more precisely, the rotational feedback on the sea level equation, has been mathematically described by the sea level equation extended for the term that is proportional to perturbation in the centrifugal potential and the second-degree tidal Love number. The perturbation in the centrifugal force due to changes in the Earth's rotational dynamics enters not only into the sea level equation, but also into the conservation law of linear momentum such that the internal viscoelastic force, the perturbation in the gravitational force and the perturbation in the centrifugal force are in balance. Adding the centrifugal-force perturbation to the linear-momentum balance creates an additional rotational feedback on the viscoelastic deformations of the Earth. We term this feedback mechanism, which is studied in this paper, as the rotational feedback on the linear-momentum balance. We extend both the time-domain method for modelling the GIA response of laterally heterogeneous earth models developed by Martinec and the traditional Laplace-domain method for modelling the GIA-induced rotational response to surface loading by considering the rotational feedback on linear-momentum balance. The correctness of the mathematical extensions of the methods is validated numerically by comparing the polar-motion response to the GIA process and the rotationally induced degree 2 and order 1 spherical harmonic component of the surface vertical displacement and gravity field. We present the difference between the case where the rotational feedback on linear-momentum balance is considered against that where it is not. Numerical simulations show that the resulting difference in radial displacement and sea level change between these situations since the Last Glacial Maximum reaches values of ±25 and ±1.8 m, respectively. Furthermore, the surface deformation pattern is modified by up to 10 per cent in areas of former or ongoing glaciation, but by up to 50 per cent at the bottom of the southern Indian ocean. This also results in the movement of coastlines during the last deglaciation to differ between the two cases due to the difference in the ocean loading, which is seen for instance in the area around Hudson Bay, Canada and along the Chinese, Australian or Argentinian coastlines.
    Keywords: Gravity, Geodesy and Tides
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    Ocean contribution to seismic gravity changes: the sea level equation for seismic perturbations revisited (2014)
    Oxford University Press
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    Publication Date: 2014-09-20
    Description: During megathrust earthquakes, great ruptures are accompanied by large scale mass redistribution inside the solid Earth and by ocean mass redistribution due to bathymetry changes. These large scale mass displacements can be detected using the monthly gravity maps of the GRACE satellite mission. In recent years it has become increasingly common to use the long wavelength changes in the Earth's gravity field observed by GRACE to infer seismic source properties for large megathrust earthquakes. An important advantage of space gravimetry is that it is independent from the availability of land for its measurements. This is relevant for observation of megathrust earthquakes, which occur mostly offshore, such as the $M_{\text{w}} \sim 9$ 2004 Sumatra–Andaman, 2010 Maule (Chile) and 2011 Tohoku-Oki (Japan) events. In Broerse et al. , we examined the effect of the presence of an ocean above the rupture on long wavelength gravity changes and showed it to be of the first order. Here we revisit the implementation of an ocean layer through the sea level equation and compare the results with approximated methods that have been used in the literature. One of the simplifications usually lies in the assumption of a globally uniform ocean layer. We show that especially in the case of the 2010 Maule earthquake, due to the closeness of the South American continent, the uniform ocean assumption is not valid and causes errors up to 57 per cent for modelled peak geoid height changes (expressed at a spherical harmonic truncation degree of 40). In addition, we show that when a large amount of slip occurs close to the trench, horizontal motions of the ocean floor play a mayor role in the ocean contribution to gravity changes. Using a slip model of the 2011 Tohoku-Oki earthquake that places the majority of slip close to the surface, the peak value in geoid height change increases by 50 per cent due to horizontal ocean floor motion. Furthermore, we test the influence of the maximum spherical harmonic degree at which the sea level equation is performed for sea level changes occurring along coastlines, which shows to be important for relative sea level changes occurring along the shore. Finally, we demonstrate that ocean floor loading, self-gravitation of water and conservation of water mass are of second order importance for coseismic gravity changes. When GRACE observations are used to determine earthquake parameters such as seismic moment or source depth, the uniform ocean layer method introduces large biases, depending on the location of the rupture with respect to the continent. The same holds for interpreting shallow slip when horizontal motions are not properly accounted for in the ocean contribution. In both cases the depth at which slip occurs will be underestimated.
    Keywords: Gravity, Geodesy and Tides
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    Investigating long-term subsidence at Medicine Lake Volcano, CA, using multitemporal InSAR (2014)
    Oxford University Press
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    Publication Date: 2014-09-07
    Description: Long-term volcanic subsidence provides insight into intereruptive processes, which comprise the longest portion of the eruptive cycle. Ground-based geodetic surveys of Medicine Lake Volcano (MLV), northern CA, document subsidence at rates of ~–10 mm yr –1 between 1954 and 2004. The long observation period plus the duration and stable magnitude of this signal presents an ideal opportunity to study long-term volcanic deformation, but this first requires accurate knowledge of the geometry and magnitude of the source. Best-fitting analytical source models to past levelling and GPS data sets show conflicting source parameters—primarily the model depth. To overcome this, we combine multiple tracks of InSAR data, each with a different look angle, to improve upon the spatial resolution of ground-based measurements. We compare the results from InSAR to those of past geodetic studies, extending the geodetic record to 2011 and demonstrating that subsidence at MLV continues at ~–10 mm yr –1 . Using geophysical inversions, we obtain the best-fitting analytical source model—a sill located at 9–10 km depth beneath the caldera. This model geometry is similar to those of past studies, providing a good fit to the high spatial density of InSAR measurements, while accounting for the high ratio of vertical to horizontal deformation derived from InSAR and recorded by existing levelling and GPS data sets. We discuss possible causes of subsidence and show that this model supports the hypothesis that deformation at MLV is driven by tectonic extension, gravitational loading, plus a component of volume loss at depth, most likely due to cooling and crystallization within the intrusive complex that underlies the edifice. Past InSAR surveys at MLV, and throughout the Cascades, are of variable success due to dense vegetation, snow cover and atmospheric artefacts. In this study, we demonstrate how InSAR may be successfully used in this setting by applying a suite of multitemporal analysis methods that account for atmospheric and orbital noise sources. These methods include: a stacking strategy based upon the noise characteristics of each data set; pixelwise rate-map formation (-RATE) and persistent scatterer InSAR (StaMPS).
    Keywords: Gravity, Geodesy and Tides
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    The coseismic slip distribution of a shallow subduction fault constrained by prior information: the example of 2011 Tohoku (Mw 9.0) megathrust earthquake (2014)
    Oxford University Press
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    Publication Date: 2014-09-11
    Description: In the literature, the inverted coseismic slip models from seismological and geodetic data for the 2011 Tohoku-Oki earthquake portray significant discrepancies, in particular regarding the intensity and the distribution of the rupture near the trench. For a megathrust earthquake, it is difficult to discern the slip along the shallow part of the fault from the geodetic data, which are often acquired on land. In this paper, we discuss the uncertainties in the slip distribution inversion using the geodetic data for the 2011 Tohoku earthquake and the Fully Bayesian Inversion method. These uncertainties are due to the prior information regarding the boundary conditions at the edges of the fault, the dip subduction angle and the smoothing operator. Using continuous GPS data from the Japan Island, the results for the rigid and free boundary conditions show that they produce remarkably different slip distributions at shallow depths, with the latter producing a large slip exceeding 30 m near the surface. These results indicate that the smoothing operator (gradient or Laplacian schemes) does not severely affect the slip pattern. To better invert the coseismic slip, we then introduce the ocean bottom GPS (OB-GPS) data, which improve the resolution of the shallow part of the fault. We obtain a near-trench slip greater than 40 m that reaches the Earth's surface, regardless of which boundary condition is used. Additionally, we show that using a mean dip angle for the fault as derived from subduction models is adequate if the goal is to invert for the general features of the slip pattern of this megathrust event.
    Keywords: Gravity, Geodesy and Tides
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    Desmoothing of averaged periodical signals for geodetic applications (2015)
    Oxford University Press
    Details
    Publication Date: 2015-04-01
    Description: In general, observations are normally considered to refer to an epoch in time, however, observations take time. During this time span temporal variations of the observable alias the measurement. Similar phenomenon can be defined in the space domain as well: data treated to refer to a geographical location often contains integrated information of the surroundings. In each case the appropriate signal content can partially be recovered by desmoothing the averaged data. The present study delivers the theoretical foundation of a desmoothing method, and suggests its use on different applications in geodesy. The theoretical formulation of the desmoothing has been derived for 1-D and 2-D signals, the latter is interpreted on a plain and also on a sphere. The presented case studies are less elaborated, but intended to demonstrate the need and usefulness of the desmoothing tool.
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
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    Estimation of offsets in GPS time-series and application to the detection of earthquake deformation in the far-field (2015)
    Oxford University Press
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    Publication Date: 2015-01-08
    Description: Extracting geophysical signals from Global Positioning System (GPS) coordinate time-series is a well-established practice that has led to great insights into how the Earth deforms. Often small discontinuities are found in such time-series and are traceable to either broad-scale deformation (i.e. earthquakes) or discontinuities due to equipment changes and/or failures. Estimating these offsets accurately enables the identification of coseismic deformation estimates in the former case, and the removal of unwanted signals in the latter case which then allows tectonic rates to be estimated more accurately. We develop a method to estimate accurately discontinuities in time series of GPS positions at specified epochs, based on a so-called ‘offset series’. The offset series are obtained by varying the amount of GPS data before and after an event while estimating the offset. Two methods, a mean and a weighted mean method, are then investigated to produce the estimated discontinuity from the offset series. The mean method estimates coseismic offsets without making assumptions about geophysical processes that may be present in the data (i.e. tectonic rate, seasonal variations), whereas the weighted mean method includes estimating coseismic offsets with a model of these processes. We investigate which approach is the most appropriate given certain lengths of available data and noise within the time-series themselves. For the Sumatra–Andaman event, with 4.5 yr of pre-event data, we show that between 2 and 3 yr of post-event data are required to produce accurate offset estimates with the weighted mean method. With less data, the mean method should be used, but the uncertainties of the estimated discontinuity are larger.
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
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    Detection of gravity field source boundaries using deconvolution method (2014)
    Oxford University Press
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    Publication Date: 2014-10-16
    Description: Complications arise in the interpretation of gravity fields because of interference from systematic degradations, such as boundary blurring and distortion. The major sources of these degradations are the various systematic errors that inevitably occur during gravity field data acquisition, discretization and geophysical forward modelling. To address this problem, we evaluate deconvolution method that aim to detect the clear horizontal boundaries of anomalous sources by the suppression of systematic errors. A convolution-based multilayer projection model, based on the classical 3-D gravity field forward model, is innovatively derived to model the systematic error degradation. Our deconvolution algorithm is specifically designed based on this multilayer projection model, in which three types of systematic error are defined. The degradations of the different systematic errors are considered in the deconvolution algorithm. As the primary source of degradation, the convolution-based systematic error is the main object of the multilayer projection model. Both the random systematic error and the projection systematic error are shown to form an integral part of the multilayer projection model, and the mixed norm regularization method and the primal-dual optimization method are therefore employed to control these errors and stabilize the deconvolution solution. We herein analyse the parameter identification and convergence of the proposed algorithms, and synthetic and field data sets are both used to illustrate their effectiveness. Additional synthetic examples are specifically designed to analyse the effects of the projection systematic error, which is caused by the uncertainty associated with the estimation of the impulse response function.
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
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    Topics: Geosciences
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    Investigating possible gravity change rates expected from long-term deep crustal processes in Taiwan (2014)
    Oxford University Press
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    Publication Date: 2014-06-21
    Description: We propose to test if gravimetry can prove useful in discriminating different models of long-term deep crustal processes in the case of the Taiwan mountain belt. We discuss two existing tectonic models that differ in the deep processes proposed to sustain the long-term growth of the orogen. One model assumes underplating of the uppermost Eurasian crust with subduction of the deeper part of the crust into the mantle. The other one suggests the accretion of the whole Eurasian crust above crustal-scale ramps, the lower crust being accreted into the collisional orogen. We compute the temporal gravity changes caused only by long-term rock mass transfers at depth for each of them. We show that the underplating model implies a rate of gravity change of –6 x 10 –2 μGal yr –1 , a value that increases to 2 x 10 –2 μGal yr –1 if crustal subduction is neglected. If the accretion of the whole Eurasian crust occurs, a rate of 7 x 10 –2 μGal yr –1 is obtained. The two models tested differ both in signal amplitude and spatial distribution. The yearly gravity changes expected by long-term deep crustal mass processes in Taiwan are two orders of magnitude below the present-day uncertainty of land-based gravity measurements. Assuming that these annually averaged long-term gravity changes will linearly accumulate with ongoing mountain building, multidecadal time-series are needed to identify comparable rates of gravity change. However, as gravity is sensitive to any mass redistribution, effects of short-term processes such as seismicity and surface mass transfers (erosion, sedimentation, ground-water) may prevent from detecting any long-term deep signal. This study indicates that temporal gravity is not appropriate for deciphering the long-term deep crustal processes involved in the Taiwan mountain belt.
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
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    Topics: Geosciences
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    Post-earthquake relaxation using a spectral element method: 2.5-D case (2014)
    Oxford University Press
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    Publication Date: 2014-06-21
    Description: The computation of quasi-static deformation for axisymmetric viscoelastic structures on a gravitating spherical earth is addressed using the spectral element method (SEM). A 2-D spectral element domain is defined with respect to spherical coordinates of radius and angular distance from a pole of symmetry, and 3-D viscoelastic structure is assumed to be azimuthally symmetric with respect to this pole. A point dislocation source that is periodic in azimuth is implemented with a truncated sequence of azimuthal order numbers. Viscoelasticity is limited to linear rheologies and is implemented with the correspondence principle in the Laplace transform domain. This leads to a series of decoupled 2-D problems which are solved with the SEM. Inverse Laplace transform of the independent 2-D solutions leads to the time-domain solution of the 3-D equations of quasi-static equilibrium imposed on a 2-D structure. The numerical procedure is verified through comparison with analytic solutions for finite faults embedded in a laterally homogeneous viscoelastic structure. This methodology is applicable to situations where the predominant structure varies in one horizontal direction, such as a structural contrast across (or parallel to) a long strike-slip fault.
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
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    Decadal geodetic variations in Ny-Alesund (Svalbard): role of past and present ice-mass changes (2014)
    Oxford University Press
    Details
    Publication Date: 2014-06-21
    Description: The geodetic rates for the gravity variation and vertical uplift in polar regions subject to past and present-day ice-mass changes (PDIMCs) provide important insight into the rheological structure of the Earth. We provide an update of the rates observed at Ny-Ålesund, Svalbard. To do so, we extract and remove the significant seasonal content from the observations. The rate of gravity variations, derived from absolute and relative gravity measurements, is –1.39 ± 0.11 μGal yr –1 . The rate of vertical displacements is estimated using GPS and tide gauge measurements. We obtain 7.94 ± 0.21 and 8.29 ± 1.60 mm yr –1 , respectively. We compare the extracted signal with that predicted by GLDAS/Noah and ERA-interim hydrology models. We find that the seasonal gravity variations are well-represented by local hydrology changes contained in the ERA-interim model. The phase of seasonal vertical displacements are due to non-local continental hydrology and non-tidal ocean loading. However, a large part of the amplitude of the seasonal vertical displacements remains unexplained. The geodetic rates are used to investigate the asthenosphere viscosity and lithosphere/asthenosphere thicknesses. We first correct the updated geodetic rates for those induced by PDIMCs in Svalbard, using published results, and the sea level change due to the melting of the major ice reservoirs. We show that the latter are at the level of the geodetic rate uncertainties and are responsible for rates of gravity variations and vertical displacements of –0.29 ± 0.03 μGal yr –1 and 1.11 ± 0.10 mm yr –1 , respectively. To account for the late Pleistocene deglaciation, we use the global ice evolution model ICE-3G. The Little Ice Age (LIA) deglaciation in Svalbard is modelled using a disc load model with a simple linear temporal evolution. The geodetic rates at Ny-Ålesund induced by the past deglaciations depend on the viscosity structure of the Earth. We find that viscous relaxation time due to the LIA deglaciation in Svalbard is more than 60 times shorter than that due to the Pleistocene deglaciation. We also find that the response to past and PDIMCs of an Earth model with asthenosphere viscosities ranging between 1.0 and 5.5 x 10 18 Pa s and lithosphere (resp. asthenosphere) thicknesses ranging between 50 and 100 km (resp. 120 and 170 km) can explain the rates derived from geodetic observations.
    Keywords: Gravity, Geodesy and Tides
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    Topics: Geosciences
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    Application of the {chi}2 principle and unbiased predictive risk estimator for determining the regularization parameter in 3-D focusing gravity inversion (2014)
    Oxford University Press
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    Publication Date: 2014-11-16
    Description: The 2 principle and the unbiased predictive risk estimator are used to determine optimal regularization parameters in the context of 3-D focusing gravity inversion with the minimum support stabilizer. At each iteration of the focusing inversion the minimum support stabilizer is determined and then the fidelity term is updated using the standard form transformation. Solution of the resulting Tikhonov functional is found efficiently using the singular value decomposition of the transformed model matrix, which also provides for efficient determination of the updated regularization parameter each step. Experimental 3-D simulations using synthetic data of a dipping dike and a cube anomaly demonstrate that both parameter estimation techniques outperform the Morozov discrepancy principle for determining the regularization parameter. Smaller relative errors of the reconstructed models are obtained with fewer iterations. Data acquired over the Gotvand dam site in the south-west of Iran are used to validate use of the methods for inversion of practical data and provide good estimates of anomalous structures within the subsurface.
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
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    Topics: Geosciences
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    Spectral-finite element approach to post-seismic relaxation in a spherical compressible Earth: application to gravity changes due to the 2004 Sumatra-Andaman earthquake (2014)
    Oxford University Press
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    Publication Date: 2014-11-19
    Description: Global navigation satellite systems (GNSSs) have revealed that a mega-thrust earthquake that occurs in an island-arc trench system causes post-seismic crustal deformation. Such crustal deformation data have been interpreted by combining three mechanisms: afterslip, poroelastic rebound and viscoelastic relaxation. It is seismologically important to determine the contribution of each mechanism because it provides frictional properties between the plate boundaries and viscosity estimates in the asthenosphere which are necessary to evaluate the stress behaviour during earthquake cycles. However, the observation sites of GNSS are mostly deployed over land and can detect only a small part of the large-scale deformation, which precludes a clear separation of the mechanisms. To extend the spatial coverage of the deformation area, recent studies started to use satellite gravity data that can detect long-wavelength deformations over the ocean. To date, compared with theoretical models for calculating the post-seismic crustal deformation, a few models have been proposed to interpret the corresponding gravity variations. Previous approaches have adopted approximations for the effects of compressibility, sphericity and self-gravitation when computing gravity changes. In this study, a new spectral-finite element approach is presented to consider the effects of material compressibility for Burgers viscoelastic earth model with a laterally heterogeneous viscosity distribution. After the basic principles are explained, it is applied to the 2004 Sumatra–Andaman earthquake. For this event, post-seismic deformation mechanisms are still a controversial topic. Using the developed approach, it is shown that the spatial patterns of gravity change generated by the above three mechanisms clearly differ from one another. A comparison of the theoretical simulation results with the satellite gravity data obtained from the Gravity Recovery and Climate Experiment reveals that both afterslip and viscoelastic relaxation are occurring. Considering the spatial patterns in satellite gravity fields is an effective method for investigating post-seismic deformation mechanisms.
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
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    Topics: Geosciences
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    Characterization of geothermally relevant structures at the top of crystalline basement in Switzerland by filters and gravity forward modelling (2014)
    Oxford University Press
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    Publication Date: 2014-08-07
    Description: Some of the major geothermal anomalies in central Europe are linked to tectonic structures within the top of crystalline basement, which modify strongly the top of this basement. Their assessment is a major challenge in exploration geophysics. Gravity has been proven to be suitable for the detection of mainly large scale lithological and structural inhomogeneities. Indeed, it is well known and proven by different wells that, for example, in northern Switzerland extended negative anomalies are linked to such structures. Due to depth limitation of wells, there vertical extension is often unknown. In this study, we have investigated the potential of gravity for the geometrical characterization of such basement structures. Our approach consists in the combination of the series of Butterworth filters, geological modelling and best-fitting between observed and computed residual anomalies. In this respect, filters of variable wavelength are applied to observed and computed gravity data. The geological model is discretized into a finite element mesh. Near-surface anomalies and the effect of the sedimentary cover were eliminated using cut-off wavelength of 10 km and geological and seismic information. We analysed the potential of preferential Butterworth filtering in a sensitivity study and applied the above mentioned approach to part of the Swiss molasses basin. Sensitivity analyses reveal that such sets of residual anomalies represents a pseudo-tomography revealing the distribution of different structures with depth. This finding allows for interpreting negative anomalies in terms of 3-D volumes. Best-fitting then permits determination of the most likely 3-D geometries of such basement structures. Our model fits both, geological observations and gravity: among 10 deep boreholes in the studied area, six reach the respective units and confirm our distribution of the negative (and positive) anomalies.
    Keywords: Gravity, Geodesy and Tides
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    Topics: Geosciences
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    Spherical harmonic analysis of a harmonic function given on a spheroid (2016)
    Oxford University Press
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    Publication Date: 2016-05-14
    Description: A new analytical method for the computation of a truncated series of solid spherical harmonic coefficients (HCs) from data on a spheroid (i.e. an oblate ellipsoid of revolution) is derived, using a transformation between surface and solid spherical HCs. A two-step procedure is derived to extend this transformation beyond degree and order (d/o) 520. The method is compared to the Hotine–Jekeli transformation in a numerical study based on the EGM2008 global gravity model. Both methods are shown to achieve submicrometre precision in terms of height anomalies for a model to d/o 2239. However, both methods result in spherical harmonic models that are different by up to 7.6 mm in height anomalies and 2.5 mGal in gravity disturbances due to the different coordinate system used. While the Hotine–Jekeli transformation requires the use of an ellipsoidal coordinate system, the new method uses only spherical polar coordinates. The Hotine–Jekeli transformation is numerically more efficient, but the new method can more easily be extended to cases where (a linear combination of) normal derivatives of the function under consideration are given on the surface of the spheroid. It therefore provides a solution to many types of ellipsoidal boundary-value problems in the spectral domain.
    Keywords: Gravity, Geodesy and Tides
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    Topics: Geosciences
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    Observations of ocean tidal load response in South America from subdaily GPS positions (2016)
    Oxford University Press
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    Publication Date: 2016-04-29
    Description: We explore Earth's elastic deformation response to ocean tidal loading (OTL) using kinematic Global Positioning System (GPS) observations and forward-modelled predictions across South America. Harmonic coefficients are extracted from up to 14 yr of GPS-inferred receiver locations, which we estimate at 5 min intervals using precise point positioning. We compare the observed OTL-induced surface displacements against predictions derived from spherically symmetric, non-rotating, elastic and isotropic (SNREI) Earth models. We also compare sets of modelled predictions directly for various ocean-tide and Earth-model combinations. The vector differences between predicted displacements computed using separate ocean-tide models reveal uniform-displacement components common to all stations in the South America network. Removal of the network-mean OTL-induced displacements from each site substantially reduces the vector differences between observed and predicted displacements. We focus on the dominant astronomical tidal harmonics from three distinct frequency bands: semidiurnal (M 2 ), diurnal (O 1 ) and fortnightly (M f ). In each band, the observed OTL-induced surface displacements strongly resemble the modelled displacement-response patterns, and the residuals agree to about 0.3 mm or better. Even with the submillimetre correspondence between observations and predictions, we detect regional-scale spatial coherency in the final set of residuals, most notably for the M 2 harmonic. The spatial coherency appears relatively insensitive to the specific choice of ocean-tide or SNREI-Earth model. Varying the load model or 1-D elastic structure yields predicted OTL-induced displacement differences of order 0.1 mm or less for the network. Furthermore, estimates of the observational uncertainty place the noise level below the magnitude of the residual displacements for most stations, supporting our interpretation that random errors cannot account for the entire misfit. Therefore, the spatially coherent residuals may reveal deficiencies in the a priori SNREI Earth models. In particular, the residuals may indicate sensitivity to regional deviations from standard globally averaged Earth structure due to the presence of the South American craton.
    Keywords: Gravity, Geodesy and Tides
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    A new hybrid inversion method for parametric curved faults and its application to the 2008 Wenchuan (China) earthquake (2016)
    Oxford University Press
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    Publication Date: 2016-03-20
    Description: Planar faults are widely adopted during inversions to determine slip distributions and fault geometries using geodetic observations; however, little research has been conducted with respect to curved faults. We attribute this to the lack of an appropriate parameterized modelling method. In this paper, we present a curved-fault modelling method (CFMM) that describes a curved fault according to specific parameters, and we also develop a corresponding hybrid iterative inversion algorithm (HIIA) to perform inversions for parametric curved-fault geometries and slips. The results of the strike-component and dip-component synthetic tests show that a complex S-shaped fault surface and a circular slip distribution are successfully recovered, indicating the strong performance of the CFMM and HIIA methods. In addition, we describe and verify a scenario for determining the number of necessary geometrical parameters for the HIIA and examine the case study of the Wenchuan earthquake, which occurred on a complex listric fault surface. During the iteration process of the HIIA, both the fault geometry and slip distribution of the Beichuan and Pengguan faults converge to optimal values, indicating a Beichuan fault (BCF) model with a continuous listric shape and gradual steepening from the southwest to the northeast, which is highly consistent with geological survey results. Both the synthetic and real-world case studies show that the HIIA and the CMFF are superior to the conventional fault modelling method based on rectangular planes and that these models have the potential for use in more integrated research involving inversion studies, such as joint slip/curved-fault-geometry inversions that take into account data resolving power.
    Keywords: Gravity, Geodesy and Tides
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    Globally gridded terrestrial water storage variations from GRACE satellite gravimetry for hydrometeorological applications (2016)
    Oxford University Press
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    Publication Date: 2016-05-22
    Description: Globally gridded estimates of monthly-mean anomalies of terrestrial water storage (TWS) are estimated from the most recent GRACE release 05a of GFZ Potsdam in order to provide non-geodetic users a convenient access to state-of-the-art GRACE monitoring data. We use an ensemble of five global land model simulations with different physics and different atmospheric forcing to obtain reliable gridded scaling factors required to correct for spatial leakage introduced during data processing. To allow for the application of this data-set for large-scale monitoring tasks, model validation efforts, and subsequently also data assimilation experiments, globally gridded estimates of TWS uncertainties that include (i) measurement, (ii) leakage and (iii) re-scaling errors are provided as well. The results are generally consistent with the gridded data provided by Tellus, but deviate in some basins which are largely affected by the uncertainties of the model information required for re-scaling, where the approach based on the median of a small ensemble of global land models introduced in this paper leads to more robust results.
    Keywords: Gravity, Geodesy and Tides
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    Topics: Geosciences
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    Regional recovery of the disturbing gravitational potential by inverting satellite gravitational gradients (2016)
    Oxford University Press
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    Publication Date: 2016-02-10
    Description: Regional recovery of the disturbing gravitational potential in the area of Central Europe from satellite gravitational gradients data is discussed in this contribution. The disturbing gravitational potential is obtained by inverting surface integral formulas which transform the disturbing gravitational potential onto disturbing gravitational gradients in the spherical local north-oriented frame. Two numerical approaches that solve the inverse problem are considered. In the first approach, the integral formulas are rigorously decomposed into two parts, that is, the effects of the gradient data within near and distant zones. While the effect of the near zone data is sought as an inverse problem, the effect of the distant zone data is synthesized from the global gravitational model GGM05S using spectral weights given by truncation error coefficients up to the degree 150. In the second approach, a reference gravitational field up to the degree 180 is applied to reduce and smooth measured gravitational gradients. In both cases we recovered the disturbing gravitational potential from each of the four well-measured gravitational gradients of the GOCE satellite separately as well as from their combination. Obtained results are compared with the EGM2008, DIR-r2, TIM-r2 and SPW-r2 global gravitational models. The best fit was achieved for EGM2008 and the second approach combining all four well-measured gravitational gradients with rms of 1.231 m 2  s –2 .
    Keywords: Gravity, Geodesy and Tides
    Print ISSN: 0956-540X
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    Topics: Geosciences
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    Efficient modelling of gravity effects due to topographic masses using the Gauss-FFT method (2016)
    Oxford University Press
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    Publication Date: 2016-02-12
    Description: We present efficient Fourier-domain algorithms for modelling gravity effects due to topographic masses. The well-known Parker's formula originally based on the standard fast Fourier transform (FFT) algorithm is modified by applying the Gauss–FFT method instead. Numerical precision of the forward and inverse Fourier transforms embedded in Parker's formula and its extended forms are significantly improved by the Gauss–FFT method. The topographic model is composed of two major aspects, the geometry and the density. Versatile geometric representations, including the mass line model, the mass prism model, the polyhedron model and smoother topographic models interpolated from discrete data sets using high-order splines or pre-defined by analytical functions, in combination with density distributions that vary both laterally and vertically in rather arbitrary ways following exponential or general polynomial functions, now can be treated in a consistent framework by applying the Gauss–FFT method. The method presented has been numerically checked by space-domain analytical and hybrid analytical/numerical solutions already established in the literature. Synthetic and real model tests show that both the Gauss–FFT method and the standard FFT method run much faster than space-domain solutions, with the Gauss–FFT method being superior in numerical accuracy. When truncation errors are negligible, the Gauss–FFT method can provide forward results almost identical to space-domain analytical or semi-numerical solutions in much less time.
    Keywords: Gravity, Geodesy and Tides
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    Inversion of gravity gradient tensor data: does it provide better resolution? (2016)
    Oxford University Press
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    Publication Date: 2016-02-14
    Description: The gravity gradient tensor (GGT) has been increasingly used in practical applications, but the advantages and the disadvantages of the analysis of GGT components versus the analysis of the vertical component of the gravity field are still debated. We analyse the performance of joint inversion of GGT components versus separate inversion of the gravity field alone, or of one tensor component. We perform our analysis by inspection of the Picard Plot, a Singular Value Decomposition tool, and analyse both synthetic data and gradiometer measurements carried out at the Vredefort structure, South Africa. We show that the main factors controlling the reliability of the inversion are algebraic ambiguity (the difference between the number of unknowns and the number of available data points) and signal-to-noise ratio. Provided that algebraic ambiguity is kept low and the noise level is small enough so that a sufficient number of SVD components can be included in the regularized solution, we find that: (i) the choice of tensor components involved in the inversion is not crucial to the overall reliability of the reconstructions; (ii) GGT inversion can yield the same resolution as inversion with a denser distribution of gravity data points, but with the advantage of using fewer measurement stations.
    Keywords: Gravity, Geodesy and Tides
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