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  • Articles  (63)
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  • 1
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    Artificial intelligence in the sorting of municipal waste as an enabler of the circular economy (2021)
    Details
    Publication Date: 2023-05-15
    Description: The recently finalized research project "ZRR for municipal waste" aimed at testing and evaluating the automation of municipal waste sorting plants by supplementing or replacing manual sorting, with sorting by a robot with artificial intelligence (ZRR). The objectives were to increase the current recycling rates and the purity of the recovered materials; to collect additional materials from the current rejected flows; and to improve the working conditions of the workers, who could then concentrate on, among other things, the maintenance of the robots. Based on the empirical results of the project, this paper presents the main results of the training and operation of the robotic sorting system based on artificial intelligence, which, to our knowledge, is the first attempt at an application for the separation of bulky municipal solid waste (MSW) and an installation in a full-scale waste treatment plant. The key questions for the research project included (a) the design of test protocols to assess the quality of the sorting process and (b) the evaluation of the performance quality in the first six months of the training of the underlying artificial intelligence and its database.
    Keywords: ddc:600
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
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  • 2
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    Sustainable smart city : opening a black box (2021)
    Details
    Publication Date: 2023-05-15
    Description: Cities are becoming digital and are aiming to be sustainable. How they are combining the two is not always apparent from the outside. What we need is a look from inside. In recent years, cities have increasingly called themselves Smart City. This can mean different things, but generally includes a look towards new digital technologies and claim that a Smart City has various advantages for its citizens, roughly in line with the demands of sustainable development. A city can be seen as smart in a narrow sense, technology wise, sustainable or smart and sustainable. Current city rankings, which often evaluate and classify cities in terms of the target dimensions 2smart" and "sustainable", certify that some cities are both. In its most established academic definitions, the Smart City also serves both to improve the quality of life of its citizens and to promote sustainable development. Some cities have obviously managed to combine the two. The question that arises is as follows: What are the underlying processes towards a sustainable Smart City and are cities really using smart tools to make themselves sustainable in the sense of the 2015 United Nations Sustainability Goal 11? This question is to be answered by a method that has not yet been applied in research on cities and smart cities: the innovation biography. Based on evolutionary economics, the innovation biography approaches the process towards a Smart City as an innovation process. It will highlight which actors are involved, how knowledge is shared among them, what form citizen participation processes take and whether the use of digital and smart services within a Smart City leads to a more sustainable city. Such a process-oriented method should show, among other things, to what extent and when sustainability-relevant motives play a role and which actors and citizens are involved in the process at all.
    Keywords: ddc:600
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
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  • 3
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    Designing on the basis of recycling-metallurgy possibilities : material-specific rules and standards for "anti-dissipative products" (2021)
    Details
    Publication Date: 2023-05-15
    Description: The demand for metals from the entire periodic table is currently increasing due to the ongoing digitalization. However, their use within electrical and electronic equipment (EEE) poses problems as they cannot be recovered sufficiently in the end-of-life (EoL) phase. In this paper, we address the unleashed dissipation of metals caused by the design of EEE for which no globally established recycling technology exists. We describe the European Union's (EU) plan to strive for a circular economy (CE) as a political response to tackle this challenge. However, there is a lack of feedback from a design perspective. It is still unknown what the implications for products would be if politics were to take the path of a CE at the level of metals. To provide clarification in this respect, a case study for indium is presented and linked to its corresponding recycling-metallurgy of zinc and lead. As a result, a first material-specific rule on the design of so-called "anti-dissipative" products is derived, which actually supports designing EEE with recycling in mind and represents an already achieved CE on the material level. In addition, the design of electrotechnical standardization is being introduced. As a promising tool, it addresses the multi-dimensional problems of recovering metals from urban ores and assists in the challenge of enhancing recycling rates. Extending the focus to other recycling-metallurgy besides zinc and lead in further research would enable the scope for material-specific rules to be widened.
    Keywords: ddc:600
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
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  • 4
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    Getting municipal energy management systems ISO 50001 certified : a study with 28 European municipalities (2021)
    Details
    Publication Date: 2023-05-15
    Description: Managing energy use by municipalities should be an important part of local energy and climate policy. The ISO 50001 standard constitutes an internationally recognized catalogue of requirements for systematic energy management. Currently, this standard is mostly implemented by companies. Our study presents an approach where consultants supported 28 European municipalities in establishing energy management systems. A majority (71%) of these municipalities had achieved ISO 50001 certification by the end of our study. We also conducted two surveys to learn more about motivations and challenges when it comes to establishing municipal energy management systems. We found that organizational challenges and resource constraints were the most important topics in this regard. Based on the experiences in our study we present lessons learned regarding supporting municipalities in establishing energy management systems.
    Keywords: ddc:320
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
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  • 5
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    The potential and limitations of critical raw material recycling : the case of LED lamps (2021)
    Details
    Publication Date: 2023-05-15
    Description: Supply risks and environmental concerns drive the interest in critical raw material recycling in the European Union. Globally, waste electrical and electronic equipment (WEEE) is projected to increase by almost 40% until 2030. This waste stream can be a source of secondary raw materials. The determination of the economic feasibility of recycling and recovering specific materials is a data-intensive, time-consuming, and case-specific task. This study introduced a two-part evaluation scheme consisting of upper continental crust concentrations and raw material prices as a simple tool to indicate the potential and limitations of critical raw material recycling. It was applied to the case of light-emitting diodes (LED) lamps in the EU. A material flow analysis was conducted, and the projected waste amounts were analyzed using the new scheme. Indium, gallium, and the rare earth elements appeared in low concentrations and low absolute masses and showed only a small revenue potential. Precious metals represented the largest revenue share. Future research should confirm the validity and usefulness of the evaluation scheme.
    Keywords: ddc:600
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
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  • 6
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    The other side of the (policy) coin : analyzing exnovation policies for the urban mobility transition in eight cities around the globe (2021)
    Details
    Publication Date: 2023-05-15
    Description: Many cities all over the world highlight the need to transform their urban mobility systems into more sustainable ones, to confront pressing issues such as air and noise pollution, and to deliver on climate change mitigation action. While the support of innovations is high on the agenda of both national and local authorities, consciously phasing-out unsustainable technologies and practices is often neglected. However, this other side of the policy coin, "exnovation", is a crucial element for the mobility transition. We developed a framework to facilitate a more comprehensive assessment of urban mobility transition policies, systematically integrating exnovation policies. It links exnovation functions as identified in transition studies with insights from urban mobility studies and empirical findings from eight city case studies around the world. The findings suggest that most cities use some kinds of exnovation policies to address selective urban mobility issues, e.g., phasing-out diesel buses, restricting the use of polluting motor vehicles in some parts of the city, etc. Still, we found no evidence for a systematic exnovation approach alongside the innovation policies. Our framework specifies exnovation functions for the urban mobility transition by lining out policy levers and concrete measure examples. We hope that the framework inspires future in-depth research, but also political action to advance the urban mobility transition.
    Keywords: ddc:380
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
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  • 7
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    The green hydrogen puzzle : towards a German policy framework for industry (2021)
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    Publication Date: 2023-05-15
    Description: Green hydrogen will play a key role in building a climate-neutral energy-intensive industry, as key technologies for defossilising the production of steel and basic chemicals depend on it. Thus, policy-making needs to support the creation of a market for green hydrogen and its use in industry. However, it is unclear how appropriate policies should be designed, and a number of challenges need to be addressed. Based on an analysis of the ongoing German debate on hydrogen policies, this paper analyses how policy-making for green hydrogen development may support industry defossilisation. For the assessment of policy instruments, a simplified multi-criteria analysis (MCA) is used with an innovative approach that derives criteria from specific challenges. Four challenges and seven relevant policy instruments are identified. The results of the MCA reveal the potential of each of the selected instruments to address the challenges. The paper furthermore outlines how instruments might be combined in a policy package that supports industry defossilisation, creates synergies and avoids trade-offs. The paper's impact may reach beyond the German case, as the challenges are not specific to the country. The results are relevant for policy-makers in other countries with energy-intensive industries aiming to set the course towards a hydrogen future.
    Keywords: ddc:320
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
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  • 8
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    Towards a digital product passport fit for contributing to a circular economy (2021)
    Details
    Publication Date: 2023-05-15
    Description: The Digital Product Passport (DPP) is a concept of a policy instrument particularly pushed by policy circles to contribute to a circular economy. The preliminary design of the DPP is supposed to have product-related information compiled mainly by manufactures and, thus, to provide the basis for more circular products. Given the lack of scientific debate on the DPP, this study seeks to work out design options of the DPP and how these options might benefit stakeholders in a product's value chain. In so doing, we introduce the concept of the DPP and, then, describe the existing regime of regulated and voluntary product information tools focusing on the role of stakeholders. These initial results are reflected in an actor-centered analysis on potential advantages gained through the DPP. Data is generated through desk research and a stakeholder workshop. In particular, by having explored the role the DPP for different actors, we find substantial demand for further research on a variety of issues, for instance, on how to reduce red tape and increase incentives for manufacturers to deliver certain information and on how or through what data collection tool (e.g., database) relevant data can be compiled and how such data is provided to which stakeholder group. We call upon other researchers to close the research gaps explored in this paper also to provide better policy direction on the DPP.
    Keywords: ddc:320
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
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  • 9
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    Making school-based GHG-emissions tangible by student-led carbon footprint assessment program (2021)
    Details
    Publication Date: 2023-05-15
    Description: Schools play an important role in achieving climate protection goals, because they lay the foundation of knowledge for a responsible next generation. Therefore, schools as institutions have a special role model function. Enabling schools to become aware of their own carbon footprint (CF) is an important prerequisite for being able to tap the substantial CO2 reduction potential. Aiming at the direct involvement of students in the assessment process, a new assessment tool was developed within the Schools4Future project that gives students the opportunity to determine their own school's CF. With this instrument the CO2 emissions caused by mobility, heating and electricity consumption as well as for food in the school canteen and for consumables (paper) can be recorded. It also takes into account existing renewable energy sources. Through the development of the tool, not only a monitoring instrument was established but also a concrete starting point from which students could take actions to reduce Greenhouse Gas (GHG) emissions. This paper presents the tool and its methods used to calculate the CF and compares it with existing approaches. A comparative case study of four pilot schools in Germany demonstrates the practicability of the tool and reveals fundamental differences between the GHG emissions.
    Keywords: ddc:300
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
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  • 10
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    Success factors for the foundation of municipal utilities in Germany (2021)
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    Publication Date: 2023-05-15
    Description: More than 150 municipal utilities (so-called Stadtwerke) were established in Germany from the beginning of the millennium, bringing the total number of Stadtwerke currently established within the country to approximately 900. With responsibility for more than half of the supply of electricity, gas and heat in Germany, these Stadtwerke play a central role in the transformation of the energy sector, or Energiewende. In addition, due to their local and regional ties, Stadtwerke have a particular role to play in energy politics, the economy and across society. This article focuses on the motives behind, and grounds for, the current wave of newly established Stadtwerke. Further, it discusses the factors that were critical to the successful formation of new Stadtwerke in recent years. The results of our survey indicate that the establishment of municipal Stadtwerke is a suitable measure to implement the energy transition at the local level, whereby the concept of public value has a high level of importance for the local decision-makers. Collaboration and cooperation, as well as a resilience-oriented strategy, are important success factors for new Stadtwerke.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
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  • 11
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    The circular business framework for building, developing and steering businesses in the circular economy (2021)
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    Publication Date: 2023-05-15
    Description: The need for a transition towards a circular economy (CE) is evident, as the current economic model is based on the exploitation of far more resources than the planet can replenish sustainably. A significant part of this economic transition is the inception of new, CE-oriented startups and business activities. While business model frameworks (BMF), such as the Business Model Canvas (BMC), were at the center of discussions about structuring business ideas in the beginning of the millennium, the conversation must now shift towards circular BMFs (CBMF). This paper follows the Design Research Methodology (DRM) for an empirical approach to devising a novel CBMF, including expert interviews as well as a first application of the framework with a startup. Throughout this process, a new and innovative tool called Circular Business Framework (CBF) was created and tested based on CE principles.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
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  • 12
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    Holistic evaluation of digital applications in the energy sector : evaluation framework development and application to the use case smart meter roll-out (2021)
    Details
    Publication Date: 2023-05-15
    Description: The development of digital technologies is accelerating, enabling increasingly profound changes in increasingly short time periods. The changes affect almost all areas of the economy as well as society. The energy sector has already seen some effects of digitalization, but more drastic changes are expected in the next decades. Besides the very positive impacts on costs, system stability, and environmental effects, potential obstacles and risks need to be addressed to ensure that advantages can be exploited while adverse effects are avoided. A good understanding of available and future digital applications from different stakeholders' perspectives is necessary. This study proposes a framework for the holistic evaluation of digital applications in the energy sector. The framework consists of a combination of well-established methods, namely the multi-criteria analysis (MCA), the life cycle assessment (LCA), and expert interviews. The objective is to create transparency on benefits, obstacles, and risks as a basis for societal and political discussions and to supply the necessary information for the sustainable development and implementation of digital applications. The novelty of the proposed framework is the specific combination of the three methods and its setup to enable sound applicability to the wide variety of digital applications in the energy sector. The framework is tested subsequently on the example of the German smart meter roll-out. The results reveal that, on the one hand, the smart meter roll-out clearly offers the potential to increase the system stability and decrease the carbon emission intensity of the energy system. Therefore, the overall evaluation from an environmental perspective is positive. However, on the other hand, close attention needs to be paid to the required implementation and operational effort, the IT (information technology) and data security, the added value for the user, the social acceptance, and the realization of energy savings. Therefore, the energy utility perspective in particular results in an overall negative evaluation. Several areas with a need for action are identified. Overall, the proposed framework proves to be suitable for the holistic evaluation of this digital application.
    Keywords: ddc:600
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
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  • 13
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    Sustainable transformation of Jordan's energy system : development of a phase model (2021)
    Amman : Friedrich-Ebert-Stiftung
    Details
    Publication Date: 2024-01-18
    Description: A clear understanding of socio-technical interdependencies and a structured vision are prerequisites for fostering and steering a transition to a fully renewables-based energy system. To facilitate such understanding, a phase model for the renewable energy (RE) transition in the Middle East and North Africa (MENA) countries has been developed and applied to the country case of Jordan. It is designed to support the strategy development and to serve as a guide for decision-makers. The analysis shows that Jordan has taken essential steps towards a RE transition. According to the MENA energy transition phase model, Jordan can be classified as being in a transitional stage between the first phase, "Take-Off Renewables", and the second phase, "System Integration". However, fossil fuels continue to play a dominant role in the Jordanian energy sector, and the fluctuating world market prices for fossil fuels impact the economy. The expansion of domestically produced RE could significantly contribute to reducing Jordan's high imports of fossil fuels. This simultaneously increases energy security and reduces the trade deficit. To move towards a sustainable energy system, Jordan needs to embrace comprehensive flexibility measures. These include developing storage options, improving load management, upgrading the existing grid infrastructure, enhancing energy efficiency, exploring the electrification of end use sectors, and creating strong cooperation between stakeholders.
    Keywords: ddc:600
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
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  • 14
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    High-Resolution Crustal S-wave Velocity Model and Moho Geometry Beneath the Southeastern Alps: New Insights From the SWATH-D Experiment (2021)
    In:  Frontiers in Earth Science
    Details
    Publication Date: 2023-01-10
    Description: We compiled a dataset of continuous recordings from the temporary and permanent seismic networks to compute the high-resolution 3D S-wave velocity model of the Southeastern Alps, the western part of the external Dinarides, and the Friuli and Venetian plains through ambient noise tomography. Part of the dataset is recorded by the SWATH-D temporary network and permanent networks in Italy, Austria, Slovenia and Croatia between October 2017 and July 2018. We computed 4050 vertical component cross-correlations to obtain the empirical Rayleigh wave Green’s functions. The dataset is complemented by adopting 1804 high-quality correlograms from other studies. The fast-marching method for 2D surface wave tomography is applied to the phase velocity dispersion curves in the 2–30 s period band. The resulting local dispersion curves are inverted for 1D S-wave velocity profiles using the non-perturbational and perturbational inversion methods. We assembled the 1D S-wave velocity profiles into a pseudo-3D S-wave velocity model from the surface down to 60 km depth. A range of iso-velocities, representing the crystalline basement depth and the crustal thickness, are determined. We found the average depth over the 2.8–3.0 and 4.1–4.3 km/s iso-velocity ranges to be reasonable representations of the crystalline basement and Moho depths, respectively. The basement depth map shows that the shallower crystalline basement beneath the Schio-Vicenza fault highlights the boundary between the deeper Venetian and Friuli plains to the east and the Po-plain to the west. The estimated Moho depth map displays a thickened crust along the boundary between the Friuli plain and the external Dinarides. It also reveals a N-S narrow corridor of crustal thinning to the east of the junction of Giudicarie and Periadriatic lines, which was not reported by other seismic imaging studies. This corridor of shallower Moho is located beneath the surface outcrop of the Permian magmatic rocks and seems to be connected to the continuation of the Permian magmatism to the deep-seated crust. We compared the shallow crustal velocities and the hypocentral location of the earthquakes in the Southern foothills of the Alps. It revealed that the seismicity mainly occurs in the S-wave velocity range between ∼3.1 and ∼3.6 km/s.
    Language: English
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  • 15
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    Fantastic PIDs and how they help you to find things (2021)
    Details
    Publication Date: 2023-01-21
    Language: English
    Type: info:eu-repo/semantics/lecture
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  • 16
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    Organic matter characteristics using lipid biomarker analysis of a rapidly eroding permafrost cliff (2021)
    PANGAEA
    Details
    Publication Date: 2023-01-27
    Description: Organic carbon (OC) stored in Arctic permafrost represents one of Earth's largest and most vulnerable terrestrial carbon pools. Amplified climate warming across the Arctic results in widespread permafrost thaw. Permafrost deposits exposed at river cliffs and coasts are particularly susceptible to thawing processes. Accelerating erosion of terrestrial permafrost along shorelines leads to increased transfer of organic matter (OM) to nearshore waters. However, the amount of terrestrial permafrost carbon and nitrogen as well as the OM quality in these deposits are still poorly quantified. Here, we characterise the sources and the quality of OM supplied to the Lena River at a rapidly eroding permafrost river shoreline cliff in the eastern part of the delta (Sobo-Sise Island). Our multi-proxy approach captures bulk elemental, molecular geochemical and carbon isotopic analyses of late Pleistocene Yedoma permafrost and Holocene cover deposits, discontinuously spanning the last ~52 ka. We show that the ancient permafrost exposed in the Sobo-Sise cliff has a high organic carbon content (mean of about 5 wt%).We found that the OM quality, which we define as the intrinsic potential to further transformation, decomposition, and mineralization, is also high as inferred by the lipid biomarker inventory. The oldest sediments stem from Marine Isotope Stage (MIS) 3 interstadial deposits (dated to 52 to 28 cal kyr BP) and is overlaid by Last Glacial MIS 2 (dated to 28 to 15 cal ka BP) and Holocene MIS 1 (dated to 7–0 cal ka BP) deposits. The relatively high average chain length (ACL) index of n-alkanes along the cliff profile indicates a predominant contribution of vascular plants to the OM composition. The elevated ratio of iso and anteiso-branched FAs relative to long chain (C ≥ 20) n-FAs in the interstadial MIS 3 and the interglacial MIS 1 deposits, suggests stronger microbial activity and consequently higher input of bacterial biomass during these climatically warmer periods. The overall high carbon preference index (CPI) and higher plant fatty acid (HPFA) values as well as high C / N ratios point to a good quality of the preserved OM and thus to a high potential of the OM for decomposition upon thaw. A decrease of HPFA values downwards along the profile probably indicates a relatively stronger OM decomposition in the oldest (MIS 3) deposits of the cliff.
    Language: English
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  • 17
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    Seismicity catalog, focal mechanism catalog and P-wave velocity structure between Pamir and Tarim (2021)
    GFZ Data Services
    Details
    Publication Date: 2023-01-28
    Description: The Pamir plateau protrudes ~300 km between the Tajik- and Tarim-basinlithosphere of Central Asia. We present a new local-seismicity catalog, a focal-mechanism catalog, and a P-wave velocity model of the of the collision system between the Pamir plateau and the Tarim basin. The data suggest a south-dipping Asian slab that overturns in its easternmost segment. The largest principal stress at depth acts normal on the slab and is orientated parallel to the plate convergence direction. In front (south) of the Asian slab, a volume of mantle with elevated velocities and lined by weak seismicity constitutes the postulated Indian mantle indenter. The data set consists of an earthquake catalog, an earthquake focal mechanism catalog and a subsurface P-wave velocity model of the central and eastern Pamir plateau and the adjacent north-western Tarim basin; between 36.8–40.0 °N and 72.2–78.0 °E. It was collected to identify the deep tectonic structures that determine the lithospheric architecture of the Pamir plateau. Earthquakes were recorded by two temporary seismic deployments. Earthquakes that occurred between 1st August 2008 and 6th June 2010 were primarily recorded by the TIPAGE network (Yuan et al., 2008); those, between 3rd August 2015 and 23rd June 2017 by the East Pamir and Sarez aftershock networks (Yuan et al., 2018a, b). The earthquake catalog contains 1,493 seismic events at depth 〉50 km. They were localized in the present 3-D velocity model. Some events were re-located with hypoDD. The focal mechanism catalog consists of double-couple fault-slip parameters for 38 events, 29 of which are newly determined using the HASH algorithm and 9 are moment tensors from Kufner et al. (2016). The P wave-velocity model has been determined using simulps from 2,264 seismic events with well-constrained P- and S-wave arrivals. It is parameterized as velocity gradients between nodes with a horizontal and vertical spacing of 40 and 15 km, respectively. Unresolved nodes were masked using a checkerboard resolution test. The full description of the methods is provided in the data description file.
    Language: English
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  • 18
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    Back‐arc extension of the Central Bransfield Basin induced by ridge–trench collision: Implications from ambient noise tomography and stress field inversion (2021)
    In:  Geophysical Research Letters
    Details
    Publication Date: 2023-01-28
    Description: The Bransfield Basin is a young (∼4 Ma) back-arc basin related to the remnant subduction of the Phoenix Plate that once existed along the entire Pacific margin of the Antarctic Peninsula. Based on a recently deployed amphibious seismic network, we use ambient noise tomography to obtain the S-wave velocity structure in the Central Bransfield Basin (CBB). Combining with the stress-field inverted from focal mechanisms, our images reveal that the CBB suffers a significant extension in the northwest-southeast direction. The extension is strongest in the northeastern CBB with associated mantle exhumation and weakens to the southwest with decoupled deformations between the upper crust and lithospheric mantle. Such an along-strike variation of extension can be explained by slab window formation and forearc rotation, which are associated with the Phoenix Plate detachment during the ridge–trench collisions at the southwest of the Hero Fracture Zone.
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  • 19
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    A Performance Assessment of Polarimetric GNSS-R Sea Level Monitoring in the Presence of Sea Surface Roughness (2021)
    In:  Proceedings
    Details
    Publication Date: 2023-07-24
    Description: Monitoring coastal sea level has gained a large socioeconomic and environmental significance. Ground-based Global Navigation Satellite System Reflectometry (GNSS-R) offers various geophysical parameters including sea surface height. We investigate a one-year dataset from January to December 2016 to evaluate the performance of GNSS-R coastal sea levels during different sea states. Our experiment setup uses three types of antenna in terms of polarization and orientation. A zenith-looking antenna tracks Right-Handed Circular Polarization (RHCP) direct signals and two sea-looking antennas capture both Left-Handed Circular Polarization (LHCP) and RHCP reflections. The Singular Spectrum Analysis (SSA) is used for extracting interferometric frequency from the data and calculating the heights. The results indicate that the height estimates from the sea-looking antennas have better accuracy compared to the zenith-looking orientation. The LHCP antenna delivers the best performance. The yearly Root Mean Square Errors (RMSE) of 5-min GNSS-R L1 water levels compared to the nearest tide gauge are 2.8 and 3.9 cm for the sea-looking antennas and 4.7 cm for the zenith-looking antenna with correlations of 97.63, 95.02, 95.35 percent, respectively. Our analysis shows that the roughness can introduce a bias to the measurements.
    Language: English
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    Source position differences between Gaia and VLBI (2021)
    In:  Proceedings
    Details
    Publication Date: 2023-04-18
    Language: English
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    IUGG Electronic Journal Vol. 21 (2021)
    IUGG Secretariat, GFZ German Research Centre for Geosciences
    Details
    Publication Date: 2023-03-03
    Description: These short, informal newsletters, issued every month on approximately the first day of the month, are intended to keep IUGG Member National Committees informed about the activities of the IUGG Associations and actions of the IUGG Secretariat. Special issues are sometimes distributed mid-month as deemed appropriate. The content usually includes a synopsis of scientific meetings during the following three months in order to illustrate the disciplinary and geographical diversity of IUGG interests. E-Journals may be forwarded to those who will benefit from the information.
    Language: English
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    Mitigation of injection-induced seismicity on undrained faults in granite using cyclic fluid injection: A laboratory study (2021)
    In:  International Journal of Rock Mechanics and Mining Sciences
    Details
    Publication Date: 2023-02-17
    Description: Cyclic fluid injection has been demonstrated as a plausibly effective and controllable strategy to mitigate the seismic risks during hydraulic stimulation. The mechanism involved remains largely unconstrained, and our ability to control the activation of critically stressed, locally undrained faults is still limited. Injection-induced activation of these faults can be one of the most threatening scenarios as they likely perturb the stability of nearby faults beyond the stimulation volume. Here, we perform a series of laboratory fluid injection tests on critically stressed, locally undrained faults in low-permeability granite to offer insights into cyclic fluid injection as a possible solution for seismic risk mitigation. Our results show that cyclic fluid injection promotes fluid pressure diffusion on the faults, but a reduction in seismic moment release depends on several cycle-related factors, such as the critical injection pressure and injection frequency. Particularly, cyclic fluid injection could be inefficient for fluid pressure diffusion if the critical injection pressure is very close to the predicted pressure at fault failure, or over-reduced to cause excess fluid injection and long-term frictional healing. A proper design of injection parameters is thus essential to balance the energy budget between the seismic energy and hydraulic energy. Our study reveals that the effectiveness of cyclic fluid injection is also dependent on fault drainage conditions, stimulation requirements, as well as dynamic responses of faulted reservoirs, which could guide the future development of cyclic fluid injection.
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    Uranium migration through the Swiss Opalinus Clay varies on the metre scale in response to differences of the stability constant of the aqueous, ternary uranyl complex Ca2UO2CO33 (2021)
    In:  Advances in Geosciences
    Details
    Publication Date: 2023-03-15
    Description: The simulation of uranium migration through the Swiss Opalinus Clay is used as an example to quantify the influence of varying values of a stability constant in the underlying thermodynamic database on the migration lengths for the repository scale. Values for the stability constant of the neutral, ternary uranyl complex Ca2UO2(CO3)3 differ in literature by up to one order of magnitude. Within the studied geochemical system, either the neutral or the anionic complex CaUO2(CO3)2−3 is the predominant one, depending on the chosen value for the neutral complex. This leads to a changed interaction with the diffuse double layers (DDL) enveloping the clay minerals and thus can potentially influence the diffusive transport of uranium. Hence, two identical scenarios only differing in the value for the stability constant of the Ca2UO2(CO3)3 complex were applied in order to quantify and compare the migration lengths of uranium on the host rock scale (50 m) after a simulation time of one million years. We ran multi-component diffusion simulations for the shaly and sandy facies in the Opalinus Clay. A difference in the stability constant of 1.33 log units changes the migration lengths by 5 to 7 m for the sandy and shaly facies, respectively. The deviation is caused by the anion exclusion effect. However, with a maximum diffusion distance of 22 m, the influence of the stability constant of the Ca2UO2(CO3)3 complex on uranium migration in the Opalinus Clay is negligible on the host rock scale.
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    IUGG Annual Report 2020 (2021)
    IUGG Secretariat, GFZ German Research Centre for Geosciences
    In:  IUGG Annual Report
    Details
    Publication Date: 2023-03-01
    Language: English
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    Does a stability constant decide on a repository permit? (2021)
    In:  Abstracts
    Details
    Publication Date: 2023-01-19
    Description: Safety of a nuclear waste repository is based to a large extent on the isolation of the radioactive waste within a suitable host rock. Clay rocks provide an option due to their very low hydraulic conductivity only allowing diffusive transport. Diffusion processes in clay formations are complex due to the diffuse double layers (DDL) enveloping the clay minerals to compensate their net surface charge and the associated different migration behaviour for cationic, anionic and neutral species. Therefore, determination of the speciation of an element in the porewater is essential to quantify migration lengths precisely. Safety assessments are based on numerical simulations to cover time periods of up to one million years and thus the predominant species of a radionuclide, dependent on the stability constants within the law of mass action, might be signififcant. In the present study, we use uranium, one of the main components in spent fuel, as an example for the diffusion in the Swiss Opalinus Clay, a potential host rock for the storage of nuclear waste. In the geochemical system, uranium is mainly present as U(VI) in ternary uranyl complexes with calcium and carbonate, whereby speciation depends on the selected thermodynamic data (Hennig et al., 2020). For instance, the stability constants for the neutral uranyl complex Ca2UO2(CO3)3 differ slightly in literature. Depending on the selected one, either the neutral or the anionic complex CaUO2(CO3)32- is the predominant species in the system with an associated varying interaction with the DDL of the clay minerals. With our one-dimensional, multi-component diffusion models we quantified the effect of the selected stability constant on the diffusion length for the host rock scale. The chemistry in the porewater of the three facies of the Opalinus Clay, shaly, sandy and carbonate-rich, plays a key role for the sorption processes (Hennig et al., 2020) as well as for the composition and thickness of the DDL and therewith the diffusive transport. Based on our results, we show, that the influence of the predominant uranium species on the migration lengths varies between the individual facies, but is overall negligible for the host rock scale. Consequently, a stability constant is not decisive for the required thickness of the host rock as geological barrier.
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    sandbox - an R tool for creating and analysing synthetic sediment sections (2021)
    GFZ Data Services
    Details
    Publication Date: 2023-01-19
    Description: sandbox is an R-tool for probabilistic numerical modelling of sediment properties. A flexible framework for definition and application of time/depth- based rules for sets of parameters for single grains that can be used to create artificial sediment profiles. Such profiles can be used for virtual sample preparation and synthetic, for instance, luminescence measurements.
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    Surrogate Model for Multi-Component Diffusion of Uranium through Opalinus Clay on the Host Rock Scale (2021)
    In:  Applied Sciences
    Details
    Publication Date: 2023-01-19
    Description: Multi-component (MC) diffusion simulations enable a process based and more preciseapproach to calculate transport and sorption compared to the commonly used single-component(SC) models following Fick’s law. The MC approach takes into account the interaction of chemicalspecies in the porewater with the diffuse double layer (DDL) adhering clay mineral surfaces. Westudied the shaly, sandy and carbonate-rich facies of the Opalinus Clay. High clay contents dominatediffusion and sorption of uranium. The MC simulations show shorter diffusion lengths than the SCmodels due to anion exclusion from the DDL. This hampers diffusion of the predominant speciesCaUO2(CO3)2−3. On the one side, species concentrations and ionic strengths of the porewater andon the other side surface charge of the clay minerals control the composition and behaviour ofthe DDL. For some instances, it amplifies the diffusion of uranium. We developed a workflow totransfer computationally intensive MC simulations to SC models via calibrated effective diffusionand distribution coefficients. Simulations for one million years depict maximum uranium diffusionlengths between 10 and 35 m. With respect to the minimum requirement of a thickness of 100 m, theOpalinus Clay seems to be a suitable host rock for nuclear waste repositories.
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    Potential Uranium Migration within the Geochemical Gradient of the Opalinus Clay System at the Mont Terri (2021)
    In:  Minerals
    Details
    Publication Date: 2023-01-19
    Description: Transport properties of potential host rocks for nuclear waste disposal are typically determined in laboratory or in-situ experiments under geochemically controlled and constant conditions. Such a homogeneous assumption is no longer applicable on the host rock scale as can be seen from the pore water profiles of the potential host rock Opalinus Clay at Mont Terri (Switzerland). The embedding aquifers are the hydro-geological boundaries, that established gradients in the 210 m thick low permeable section through diffusive exchange over millions of years. Present-day pore water profiles were confirmed by a data-driven as well as by a conceptual scenario. Based on the modelled profiles, the influence of the geochemical gradient on uranium migration was quantified by comparing the distances after one million years with results of common homogeneous models. Considering the heterogeneous system, uranium migrated up to 24 m farther through the formation depending on the source term position within the gradient and on the partial pressure of carbon dioxide pCO2 of the system. Migration lengths were almost equal for single- and multicomponent diffusion. Differences can predominantly be attributed to changes in the sorption capacity, whereby pCO2 governs how strong uranium migration is affected by the geochemical gradient. Thus, the governing parameters for uranium migration in the Opalinus Clay can be ordered in descending priority: pCO2, geochemical gradients, mineralogical heterogeneity.
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    The Mediterranean Sea we want (2021)
    In:  Ocean and Coastal Research
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    Publication Date: 2023-01-26
    Description: This paper presents major gaps and challenges for implementing the UN Decade of Ocean Science for Sustainable Development (2021-2030) in the Mediterranean region. The authors make recommendations on the scientific knowledge needs and co-design actions identified during two consultations, part of the Decade preparatory-phase, framing them in the Mediterranean Sea’s unique environmental and socio-economic perspectives. According to the ‘Mediterranean State of the Environment and Development Report 2020’ by the United Nations Environment Programme Mediterranean Action Plan and despite notable progress, the Mediterranean region is not on track to achieve and fully implement the Sustainable Development Goals of Agenda 2030. Key factors are the cumulative effect of multiple human-induced pressures that threaten the ecosystem resources and services in the global change scenario. The basin, identified as a climate change vulnerability hotspot, is exposed to pollution and rising impacts of climate change. This affects mainly the coastal zones, at increasing risk of extreme events and their negative effects of unsustainable management of key economic assets. Transitioning to a sustainable blue economy is the key for the marine environment’s health and the nourishment of future generations. This challenging context, offering the opportunity of enhancing the knowledge to define science-based measures as well as narrowing the gaps between the Northen and Southern shores, calls for a joint (re)action. The paper reviews the state of the art of Mediterranean Sea science knowledge, sets of trends, capacity development needs, specific challenges, and recommendations for each Decade’s societal outcome. In the conclusions, the proposal for a Mediterranean regional programme in the framework of the Ocean Decade is addressed. The core objective relies on integrating and improving the existing ocean-knowledge, Ocean Literacy, and ocean observing capacities building on international cooperation to reach the “Mediterranean Sea that we want
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    Preliminary analysis and evaluation of BDS-2/BDS-3 precise point positioning (2021)
    In:  Advances in Space Research
    Details
    Publication Date: 2023-10-02
    Description: Precise point positioning (PPP) is a very important function of satellite navigation system. In this contribution, the combination of BDS-2 and BDS-3 PPP is researched. To begin with, the frequency and application of BDS-2 and BDS-3 are introduced. Then, the principle of BDS-2 and BDS-3 combined PPP, the generation and estimation method of inter-system bias (ISB) are elaborated. Finally, the global satellite visibility of BDS-2 and BDS-3, the global Position Dilution of Precision (PDOP) value and the results of BDS-2/BDS-3 PPP are analyzed based on the 51-day data of 30 stations from multi-GNSS experiment (MGEX) network in 2020. The experimental results show that: (1) The number of visible satellites of BDS-2 in Asia Pacific region is 8–15, while the number of visible satellites in most parts of the western hemisphere is less than 4; the number of visible satellites of BDS-3 in the eastern hemisphere is 8–14, while the number of visible satellites in the western hemisphere is 7–11; BDS-3 is more evenly distributed in the world than BDS-2, but the number of satellites in the eastern hemisphere is also slightly more than that in the western hemisphere. (2) The root mean square (RMS) of BDS-2/BDS-3 static PPP in the East (E), North (N) and Up (U) directions are 1.0 cm, 0.6 cm and 1.7 cm respectively; the positioning accuracy of BDS-2/BDS-3 PPP in the E, N and U directions are improved by 16.7%, 14.3% and 10.5% respectively compared with BDS-3 PPP. The RMS of BDS-2/BDS-3 kinematic PPP in the E, N and U directions are 2.0 cm, 1.3 cm and 4.1 cm respectively; the positioning accuracy of BDS-2/BDS-3 PPP in the E, N and U directions are improved by 33.3%, 38.1% and 29.3% respectively compared with BDS-3 PPP. (3) Compared with BDS-3 static PPP, the convergence time of BDS-2/BDS-3 are shortened by 6.1%, 11.5%, 10.1% and 10.3% in the E, N, U and three dimensional (3D) directions respectively. Compared with BDS-2, the convergence time of BDS-3 is shortened by more than 50%. The convergence time of BDS-2/BDS-3 kinematic PPP in the E, N, U and 3D directions is shorter than BDS-3 by 31.1%, 43.8%, 38.1% and 34.6% respectively; the convergence time of BDS-3 is shorter than BDS-2 by 61.1%, 59.7%, 60.9% and 57.1% respectively. In brief, the success of BDS-3 global networking has greatly promoted the positioning performance of the entire BDS system.
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    The versatility of GNSS observations in hydrological studies (2021)
    In:  GPS and GNSS Technology in Geosciences
    Details
    Publication Date: 2023-10-02
    Description: The Gravity Recovery and Climate Experiment (GRACE) mission makes it possible to infer the land water storage, albeit at a scale of ~300 km. Land water storage can also be inverted from the Global Navigation Satellite System (GNSS) at the cost of a dense network, which is feasible for wealthier nations. Here, the concept of a single GNSS site as a hydrometeorological sensor is explored. Specifically, the crustal displacements and the integrated water vapor (IWV) are used to characterize the 2014–15 drought that jeopardized Southeast Brazil. The crustal displacements as drought indicator confirm the drought persistence during the study period, which agree with GRACE-based values (correlation coefficient [CC] ). The IWV and precipitation series are strongly correlated (CC ), whereas during months with daily IWV below approximately 20 mm, there are simultaneities with the absence of rainfall. Furthermore, GNSS-predicted land water storage agrees with GRACE results with normalized root-mean-square differences .
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    Feasibility of ERA5 integrated water vapor trends for climate change analysis in continental Europe: An evaluation with GPS (1994–2019) by considering statistical significance (2021)
    In:  Remote Sensing of Environment
    Details
    Publication Date: 2023-10-02
    Description: Although the statistical significances for the trends of integrated water vapor (IWV) are essential for a correct interpretation of climate change signals, obtaining accurate IWV trend estimates with realistic uncertainties remains a challenge. This study evaluates the feasibility of the IWV trends derived from the newly released fifth generation European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalysis (ERA5) for climate change analysis in continental Europe. This is achieved by comparing the trends derived from in-situ ground-based Global Positioning System (GPS)’s daily IWV series from 1994 to 2019 at 109 stations. The realistic uncertainties and statistical significances of the IWV trends are evaluated with the time series analysis on their noise characteristics and proper noise models. Results show that autoregressive moving average ARMA(1,1) noise model is preferred rather than the commonly assumed white noise (WN) or first-order autoregressive AR(1) noise for about 68% of the ERA5 and GPS IWV series. An improper noise model would misevaluate the trend uncertainty of an IWV time series, compared with its specific preferred noise model. For example, ARMA(1,1) may misevaluate the standard deviations of their trend estimates (0.1–0.3 kg m−2 decade−1) by 10%. Nevertheless, ARMA(1,1) is recommended as the default noise model for the ERA5 and GPS IWV series. However, the preferred noise model for each ERA5 minus GPS (E-G) IWV series should be specifically determined, because the AR(1)-related models can result in an underestimation on its trend uncertainty by 90%. In contrast, power-law (PL) model can lead to an overestimation by up to nine times. The E-G IWV trends are within −0.2–0.4 kg m−2 decade−1, indicating that the ERA5 is a potential data source of IWV trends for climate change analysis in continental Europe. The ERA5 and GPS IWV trends are consistent in their magnitudes and geographical patterns, lower in Northwest Europe (0–0.4 kg m−2 decade−1) but higher around the Mediterranean Sea (0.6–1.4 kg m−2 decade−1).
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    Test structure in some pioneer multichambered Paleozoic foraminifera (2021)
    In:  Proceedings of the National Academy of Sciences of the United States of America (PNAS)
    Details
    Publication Date: 2023-11-13
    Description: Foraminiferal wall microstructures, consistent with the molecular-based high-rank classification, are critical to understanding foraminiferal evolution and advanced taxonomic relationships. Although test structures are well documented for recent, Cenozoic, and some Mesozoic foraminifera, the diagnostic characteristics of Paleozoic taxa are largely unexplored. The majority of calcareous Paleozoic foraminifera have been assigned to the Fusulinata based on questionable homogeneously “microgranular” test wall microstructures, which have never been sufficiently documented for most taxa. We investigated the test structures of exceptionally well-preserved Devonian (Eifelian) Semitextularia thomasi, representing the first calcareous true multichambered (serial) foraminifera, and compared this species with a large fusiform Permian representative of “true” fusulinids (Neoschwagerinidae). The tests of Semitextularia thomasi display lamellar structures that are not observed in any other fossil or recent foraminiferal group. The Paleozoic foraminifera, traditionally referred to one taxon (the class Fusulinata), possess at least three contrasting test wall microstructures, representing separate high-rank taxonomic groups. Fusulinata is most likely a highly polyphyletic group that is in need of taxonomic revision. The term Fusulinata, defined as including all Paleozoic calcareous forms except Miliolida and Lagenata, is not phylogenetically meaningful and should no longer be used or should be restricted to true complex fusulinids with microgranular test structures, which appeared in the Carboniferous.
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    Stable isotopes and predation marks shed new light on ammonoid habitat depth preferences (2021)
    In:  Scientific Reports
    Details
    Publication Date: 2023-11-13
    Description: Ammonoids are extinct cephalopods with external shells which predominated in many late Paleozoic and Mesozoic marine ecosystems. Stable isotope data from ammonoid shells constitute primary tools for understanding their palaeohabitats. However, in most sedimentary successions globally the aragonitic shells of ammonoids are dissolved during fossilisation process and therefore not available for geochemical studies. We overcome this taphonomic bias by analysing the better preservable calcitic elements of the ammonoid jaws (aptychi). We study moulds and aptychi of two successive members, temporal subspecies in our interpretation, of a scaphitid evolutionary lineage from a Late Cretaceous chalk succession in Poland. In order to reconstruct their habitat depth preferences, we apply the powerful combination of stable isotope data from aptychi and co-occurring benthic and planktic foraminifera with an analysis of predation marks preserved on scaphitid specimens. On this basis we conclude that the populations of the older subspecies led a nektic, and those of the younger subspecies, a nektobenthic lifestyle. The shift in habitat depth preferences took place probably as a response of local populations to the shallowing of the sea. Previous studies largely assumed stable depth preferences for ammonoid species, genera and even higher clades. Our study casts doubts over such generalizations by pointing out that ammonoids could have been more flexible in their depth-related behaviour than anticipated.
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    Erratum toNear-Real-Time Damage Estimation for Buildings Based on Strong-Motion Recordings: An Application to Target Areas in Northeastern Italy (2021)
    In:  Seismological Research Letters
    Details
    Publication Date: 2024-01-05
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    Near-Real-Time Damage Estimation for Buildings Based on Strong-Motion Recordings: An Application to Target Areas in Northeastern Italy (2021)
    In:  Seismological Research Letters
    Details
    Publication Date: 2024-01-05
    Description: The rapid estimation of expected impacts in case of an earthquake is extremely important for emergency managers and first responders. Current near-real-time damage assessment methods rely on ground-motion estimates and exposure or fragility datasets, in some cases integrating the shaking recorded at the site (e.g., from strong-motion monitoring networks). We propose a method that estimates the expected damages on buildings based on strong-motion recordings of a seismic event. The damage assessment is based on themaximumdrift (interstory) or the displacement, which is estimated by considering in a first approximation the behavior of a specific building typology as a single-degree-offreedom oscillator. The oscillator is characterized based on the analysis of the building stock and a large number of ambient vibration measurements performed in buildings. A specific damage state occurs when the interstory drift or displacement limits available in the literature for the specific building typology are exceeded. The method, here applied to a case study in northeastern Italy, can be applied to other seismic areas worldwide to provide quick, first-level estimates of expected damages.
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    Rock Deformation Monitoring Using Monte Carlo Waveform Inversion (2021)
    In:  Journal of Geophysical Research: Solid Earth
    Details
    Publication Date: 2024-01-05
    Description: We estimate elastic and anelastic parameters and their evolution during laboratory rock deformation experiments, while developing a Monte Carlo waveform inversion. The transducer-totransducer one-source one-station active seismic data of dry and water-saturated samples are obtained from Zaima and Katayama (2018), https://doi.org/10.1029/2018JB016377. We first performed a trial-anderror estimate of the boundary conditions in order to suppress its influence on waveforms. The synthetic seismic data were generated using equivalent homogeneous models with different combinations of elastic and anelastic parameters with the aid of spectral element method. We compared them with the laboratory experimental data. Based on the comparisons, we obtained the time-lapse variations of seismic velocities and attenuation of rock samples during deformation experiments, which we interpreted as crack developments. Our simultaneous estimation of elastic and anelastic parameters allowed us to detail the dynamics prior to the rock failure.
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    Biotic and Isotopic Vestiges of Oligotrophy on Continental Shelves During Oceanic Anoxic Event 2 (2021)
    In:  Global Biogeochemical Cycles
    Details
    Publication Date: 2023-11-10
    Description: The widespread expansion of the oxygen minimum zone onto shelves has been commonly regarded as a primary cause of benthos extinction in epicratonic sea ecosystems during the Cenomanian–Turonian boundary event (CTBE). However, neither lithology, geochemical proxies, nor micropaleontological data support this hypothesis. Instead, our integrated foraminiferal and dinoflagellate cyst study, corroborated by δ13Corg and δ15Norg data, indicate that the biota were impacted by an abrupt shift to well oxygenated oligotrophic conditions and a collapse of primary productivity in the epicontinental Central European Basin. Because the event was concurrent with the development of extensive and extreme oceanic bottom water anoxia that reached the photic zone in oceanic settings, we infer that the biotic crisis in the shelf seas during Oceanic Anoxic Event 2 (OAE2), and possibly during other OAEs, was triggered by this anomalous nutrient cycling in Earth's oceans. This phenomenon was presumably associated with intensive denitrification combined with anammox activity in the deep “ammonium oceans,” which caused a significant loss of biologically reactive nitrogen from the ocean system. Impingement of ammonium-rich anoxic waters on the photic zone resulted in primary productivity based primarily on ammonium assimilation, as recorded by strongly 15N-depleted organic matter deposited in the oceans during the CTBE. We propose that, unlike in the oceanic settings, productivity in the well-oxygenated, oligotrophic epicontinental seas was nitrate-based, as evidenced by strongly 15N-enriched organic matter deposited in the contemporaneous epicontinental sea. These very high δ15Norg values (〉+5‰) were related to the spreading of shallow oceanic waters carrying 15N-enriched nitrate onto epicontinental settings.
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    Effect of centimetric freezing of the near subsurface on Rayleigh and Love wave velocity in ambient seismic noise correlations (2021)
    In:  Geophysical Journal International
    Details
    Publication Date: 2024-01-16
    Description: About a decade ago, noise-based monitoring became a key tool in seismology. One of the tools is passive image interferometry (PII), which uses noise correlation functions (NCF) to retrieve seismic velocity variations. Most studies apply PII to vertical components recording oceanic low-frequent ambient noise ( 〈 1 Hz). In this work, PII is applied to high-frequent urban ambient noise ( 〉 1 Hz) on three three-component sensors. With environmental sensors inside the subsurface and in the air, we are able to connect observed velocity variations with environmental parameters. Temperatures below 0 °C correlate well with strong shear wave velocity increases. The temperature sensors inside the ground suggest that a frozen layer of less than 5 cm thickness causes apparent velocity increases above 2  % , depending on the channel pair. The observations indicate that the different velocity variation retrieved from the different channel pairs are due to different surface wave responses inherent in the channel pairs. With dispersion curve modelling in a 1-D medium we can verify that surfaces waves of several tens of metres wavelength experience a velocity increase of several percent due to a centimetres thick frozen layer. Moreover, the model verifies that Love waves show larger velocity increases than Rayleigh waves. The findings of this study provide new insights for monitoring with PII. A few days with temperature below 0 °C can already mask other potential targets (e.g. faults or storage sites). Here, we suggest to use vertical components, which is less sensitive to the frozen layer at the surface. If the target is the seasonal freezing, like in permafrost studies, we suggest to use three-component sensors in order to retrieve the Love wave response. This opens the possibility to study other small-scale processes at the shallow subsurface with surface wave responses.
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    Assessing recently improved precession-nutation models (2021)
    In:  Abstracts
    Details
    Publication Date: 2023-12-21
    Description: In 2020 new estimations of nutation amplitudes or precession parameters have been published or presented at main meetings. The derivation of corrections to improve the current precession-nutation models was encouraged by Resolution 5 of the 2019 General Assembly of the International Association of Geodesy (IAG). Besides, the GGOS/IERS Unified Analysis Workshop held in October 2019 recommended that effort to be prioritized among the tasks of the current IAU/IAG Joint Working Group on Improving Theories and Models of the Earth’s rotation (JWG ITMER). This presentation is intended to present comparisons of some of those new semi-empirical and semi-theorical precession-nutation models developed by different authors from either VLBI solutions of individual analysis centers or combinations of them. The models recently introduced by the authors that were reported at the AGU 2020 Fall Meeting are included in this assessment.
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    Estimating the effective spatio-temporal resolution of integrated water vapor trends based on VLBI, GNSS, and weather model data (2021)
    In:  Abstracts
    Details
    Publication Date: 2023-12-20
    Description: How far apart can two space geodetic sites be located to consider the integrated water vapor (hereinafter IWV) trends as equal, from a statistical viewpoint? How to do efficient feature selection with a given IWV time series? To address these questions, we utilize spatio-temporal variations of long-term IWV trends that were estimated employing very long baseline interferometry (VLBI), Global Navigation Satellite Systems (GNSS), and numerical weather prediction data (ERA5 reanalysis). We estimate coefficients for several spatial covariance functions; Hirvonen's model proves to be the most precise for our area of interest, Greater Europe. We find that the effective spatial resolution is around 56 km (for error level (p) 〈 0.05). Our investigations indicate that among else, altitude and proximity to the ocean are key factors affecting the IWV trend decorrelation lengths. We find good agreement between the spatially varying decorrelation lengths and established climate classification systems such as the latest Köppen-Geiger model. Moreover, the IWV trend variation as a function of data span and temporal resolution has been investigated. We find that varying the temporal resolution from one hour up to 30 days does not yield a statistically significant difference (p 〈 0.05) in the IWV trend and its uncertainty, provided the inherent autocorrelation is factored in and the data span remains. We also find that given the IWV time series length, the spread calculated from the estimated trends varying the start point of the time series, follows an exponential decrease σ(Δt) = 22Δt -1.7 + 0.008.
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    The GGOS Bureau of Products and Standards (2021)
    In:  Abstracts
    Details
    Publication Date: 2023-12-20
    Description: This presentation gives a summary of the role and the activities of the Bureau of Products and Standards (BPS) to support IAG’s Global Geodetic Observing System (GGOS) in its goal to provide observations and consistent geodetic products needed to monitor, map and understand changes in the Earth’s shape, rotation and mass distribution. In its present structure, the two Committees “Earth System Modeling” and “Essential Geodetic Variables” as well as the Working Group “Towards a consistent set of parameters for the definition of a new GRS” are associated with the BPS. A key objective of the BPS is to keep track and to foster homogenization of adopted geodetic standards and conventions across all IAG components as a fundamental basis for the generation of consistent geometric and gravimetric products. Towards this aim, an updated 2nd version of the BPS inventory of standards and conventions used for the generation of IAG products has been published in the Geodesist’s Handbook 2020. In the framework of the renewing of the GGOS website, the BPS supports the GGOS Coordinating Office in particular regarding the representation of geodetic products. Furthermore, the BPS contributes to the rewriting of the IERS Conventions as Chapter Expert for Chapter 1 “General definitions and numerical standards” and interacts with external stakeholders regarding standards and conventions, such as ISO, IAU, BIPM, CODATA and the UN GGIM Subcommittee on Geodesy, including its Working Group “Data Sharing and Development of Geodetic Standards”.
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    A First Assessment of the interconnection between celestial pole offset and geomagnetic field variations (2021)
    In:  Abstracts
    Details
    Publication Date: 2023-12-20
    Description: The Global Geodetic Observing System (GGOS) of the International Association of Geodesy (IAG) provides the geodetic infrastructure needed to monitor the Earth system.. The understanding of forced temporal variations of celestial pole motion (CPM) could bring us significantly closer to meeting the GGOS goals (i.e. 1 mm accuracy and 0.1 mm/year stability on global scales in terms of the ITRF defining parameters). Besides astronomical forcing, CPM excitation depends on the processes in the fluid core and the core-mantle boundary. The same processes are responsible for the variations of the geomagnetic field (GMF). This study investigates the interconnection between the celestial pole offset (CPO) and effective geophysical processes that contribute to the Earth's rotational variation. We use the CPO time series obtained from very long baseline interferometry (VLBI) observations together with the latest GMF data such as geomagnetic jerk and magnetic dipole moment, and a state-of-the-art geomagnetic field model to explore the correlation between CPM and GMF. Our results confirm the findings of previous studies, revealing that substantial free core nutation (FCN) disturbance occurred at the epochs close to the GMJ events. The results also reveal some common features in the FCN and GMF variation, which show the potential to improve knowledge regarding the GMF's contribution to the Earth's rotation.
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    Earth Orientation Parameter Estimation by Integrating VLBI and GNSS on the Observation Level (2021)
    In:  Abstracts
    Details
    Publication Date: 2023-12-20
    Description: The terrestrial and celestial reference frames are linked by the Earth Orientation Parameters (EOP), which describe the irregularities of the Earth's rotation and are determined by the space geodetic techniques, namely, Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR), Global Navigation Satellite Systems (GNSS), and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS). The satellite geodetic techniques (SLR, GNSS, and DORIS) cannot determine the UT1-UTC or celestial pole offsets (CPO), rendering VLBI the only technique capable of determining full EOP set. On the other hand, the GNSS technique provides precise polar motion estimates due to the continuous observations from a globally distributed network. Integrating VLBI and GNSS provides the full set of EOP and guarantees a superior accuracy than any single-technique solution. In this study we focus on the integrated estimation of the full EOP set from GNSS and VLBI. Using five VLBI continuous observing campaigns (CONT05–CONT17), the GNSS and VLBI observations are processed concurrently in a common least-squares estimator. The impact of applying global ties (EOP), local ties, and tropospheric ties, and combinations thereof is investigated. The polar motion estimates in integrated solution are dominated by the huge GNSS observations, and the accuracy in terms of weighted root mean squares (WRMS) is ~40 μas compared to the IERS 14 C04 product, which is much better than that of the VLBI-only solution. The UT1-UTC and CPO in the integrated solution also show slight improvement compared to the VLBI-only solution. Moreover, the CPO agreement between the two networks in CONT17, i.e., the VLBA and IVS networks, shows an improvement of 20% to 40% in the integrated solution with different types of ties applied.
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    A ground motion based procedure to identify the earthquakes that are the most relevant for probabilistic seismic hazard analysis (2021)
    In:  Earthquake Spectra
    Details
    Publication Date: 2024-01-23
    Description: A method is proposed to identify within seismic catalogs those earthquakes that are most relevant to the seismic hazard. The approach contrasts with the classical approach to decluster the seismic catalog with the expectation that the remaining main shocks will be the relevant events for the seismic hazard analysis. We apply a time window like in the window declustering approach of Gardner and Knopoff, but the time window is motivated by relevance to engineering. A ground motion criterion replaces the spatial window. An event in the time window is included in the “Maximum Shaking Earthquake Catalog (MSEQ catalog)” if the median ground motion at its epicenter exceeds the predicted median ground motion there from the main shock, using a locally appropriate ground motion prediction equation. Ground motion can be measured by any parameter that is estimated by a ground motion prediction equation. We consider peak acceleration and spectral amplitude (SA) at periods of 0.2, 1.0, and 3.0 s. The longer period parameters systematically remove more small events. The purpose is not to produce a declustered catalog, in which each group of physically related earthquakes is represented by its largest event. Statistical properties of the MSEQ catalog somewhat resemble the corresponding declustered catalog in three tested regions, but the MSEQ catalogs all retain more large-magnitude earthquakes. The MSEQ catalog may better represent the potential hazard in a region, and thus might be considered as an alternative to a declustered catalog in developing the seismicity model for probabilistic seismic hazard analysis.
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    Probabilistic framework for regional loss assessment due to earthquake-induced liquefaction including epistemic uncertainty (2021)
    In:  Soil Dynamics and Earthquake Engineering
    Details
    Publication Date: 2024-01-30
    Description: For seismic risk assessments, ground shaking is generally considered the primary cause of building damage. However, earthquake-induced liquefaction can also create significant structural damage and losses. Predicting the expected degree of damage in structures exposed to ground failure due to liquefaction is thus essential for seismic risk assessment. There are well-established tools and methods to evaluate the seismic risk due to ground shaking. However, despite the large number of studies related to liquefaction assessments, modelling ground failure due to an earthquake is far less mature. The incorporation of liquefaction into a seismic loss estimation framework presents several challenges. The use of simplified procedures requires a multitude of assumptions, which increase the uncertainty in the loss assessment, whilst detailed approaches based on in-situ data are resource-demanding and impractical for large-scale risk analysis. To address these shortcomings, a fully probabilistic hazard and risk assessment due to liquefaction has been employed using the OpenQuake-engine and demonstrated through a case study applied to mainland Portugal. The liquefaction hazard and risk assessment framework followed in this study allows for the incorporation of both aleatory and epistemic uncertainties, which are herein explored through a sensitivity analysis.
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    Cyclic Water Injection Potentially Mitigates Seismic Risks by Promoting Slow and Stable Slip of a Natural Fracture in Granite (2021)
    In:  Rock Mechanics and Rock Engineering
    Details
    Publication Date: 2024-01-30
    Description: Induced seismicity associated with fluid injection has raised serious concerns for the safety and efficiency of geo-energy systems. Cyclic injection has recently been proposed as an alternative injection scheme to reduce the large magnitude injection-induced seismicity. However, the influence of cyclic injection on the activation of natural fractures in granite and the resulting seismic risk is not yet clear. This study investigates the injection-induced activation of a critically stressed natural fracture in a granite core sample, particularly focusing on the comparison between monotonic and cyclic water injection under pressure-controlled and volume-controlled conditions. Experimental results show that the acceleration and deceleration of fracture slip are modulated by the shear stress imbalance between the fixed shear stress and the evolving frictional strength of the fracture. Fracture slip affects the fluid pressure distribution on the fracture, which in turn regulates the frictional strength of the fracture. At a small total shear displacement (i.e., ~ 0.9 mm in this study), cyclic injection with a restricted peak injection pressure results in aseismic fracture slip at much smaller peak slip rates compared to that during the monotonic injection. On the one hand, the more uniform reduction in effective normal stress caused by cyclic injection encourages slow and stable fracture slip, characterized by the smaller peak slip rates. On the other hand, the flowback of injected fluid or suspension of injection could prevent the occurrence of fast-accelerated fracture slip during cyclic injection. However, the fracture can become unstable when it has experienced a considerable amount of total shear displacement (larger than ~ 0.9 mm in this study), and likely gained a significantly enhanced permeability. Continued injection after the unstable shut-in stage, signified by an unusual increase in slip rate and an accelerated drop in injection pressure, could result in rapid and unstable fracture slip.
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    The RAMONES Service for Rapid Assessment of Seismic Moment and Radiated Energy in Central Italy: Concepts, Capabilities, and Future Perspectives (2021)
    In:  Seismological Research Letters
    Details
    Publication Date: 2024-01-30
    Description: We present Rapid Assessment of MOmeNt and Energy Service (RAMONES), a service for disseminating through a web interface, the estimates of seismic moment (M0) and radiated energy (ER) for earthquakes occurring in central Italy with local magnitudes above 1.7. The service is based on a fully-automatic procedure developed for downloading and processing open seismological data from the European Integrated Data Archive, Italian Civil Protection repository, and Incorporated Research Institutions for Seismology (IRIS). In its actual configuration, RAMONES uses the seismic catalog generated through the event webservice of the Italian Institute of Geophysics and Volcanology (compliant with International Federation of Digital Seismograph Networks standards) to guide the data download. The concept of RAMONES is to estimate M0 and ER from features extracted directly from recordings, namely the S-wave peak displacement (PDS) and the integral of the squared velocity (IV2S) evaluated over the S-wave window at local distances. A data set composed of 6515 earthquakes recorded in central Italy between 2008 and 2018 was used to calibrate the attenuation models relating M0 to PDS and ER to IV2S, including station corrections. The calibration values for M0 and ER were extracted from the source spectra obtained by applying a decomposition approach to the Fourier amplitude spectra known as the generalized inversion technique. To test the capabilities of RAMONES, we validate the attenuation models by performing residual analysis over about 60 earthquakes occurring in 2019 that were used for the spectral decomposition analysis but not considered in the calibration phase. Since January 2020, a testing operational phase has been running, and RAMONES has analyzed about 800 earthquakes by September 2020. The distribution of the source parameters and their relevant scaling relationships are automatically computed and disseminated in the form of maps, parametric tables, figures, and reports available through the RAMONES web interface.
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    Laboratory hydraulic fracturing experiments on crystalline rock for geothermal purposes (2021)
    In:  Earth-Science Reviews
    Details
    Publication Date: 2024-01-30
    Description: This article reviews laboratory experimental studies on hydraulic fracturing under triaxial and true triaxial stress conditions in crystalline rock for geothermal purposes, and places particular focus on the stimulation of Enhanced Geothermal Systems. First, parameters that influence hydraulic fracture initiation and propagation and breakdown pressure are reviewed and discussed. The parameters including micro-structure, fluid viscosity, injection rate, and fluid infiltration, and stress conditions are identified as the key controlling factors in hydraulic fracture growth in hard rock. Second, innovative injection schemes, such as cyclic and fatigue hydraulic fracturing, are reviewed because they show advantages both in fracture network creation in granite and in mitigating and controlling induced seismicity via fluid injection. Third, this review includes fracture-inspection techniques, non-destructive methods of acoustic emission (AE) monitoring and X-ray computed tomography (CT), and microscopic observations used for quantifying the efficiency of injection protocols. In addition to AE parameters, such as AE event rate and source location, we emphasize the importance of in-depth AE analysis on the failure mode and radiated seismic energy. X-ray CT and microscopic observation enable fractures in the rock volume to be quantified, and thereby lead to a better understanding the mechanism behind hydraulic fracturing. Combined measurements of AE and CT yield insights into the complex process of hydraulic fracture and permeability enhancement. The discussion section is enriched with diagrams that connect the injection rate and the resulting fluid infiltration zone and fracture process zone, granite-specific hydraulic fracturing behavior, and practical upscaling elements for potential field applications in geothermal fields.
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    Impact of partially non-ergodic site-specific probabilistic seismic hazard on risk assessment of single buildings (2021)
    In:  Earthquake Spectra
    Details
    Publication Date: 2024-01-30
    Description: The growth of global ground-motion databases has allowed generation of nonergodic ground-motion prediction equations (GMPEs) based on specific on-site recordings. Several studies have investigated the differences between the hazard estimates from ergodic versus non-ergodic GMPEs. Here instead we focus on the impact of non-ergodic PSHA estimates on the seismic risk of nonlinear single-degree-of-freedom systems representing ductile structures and compare it with the traditional risk estimates obtained using ergodic GMPEs. The structure-and-site-specific risk estimates depend not only on the difference in the hazard estimates but also on the different hazard-consistent ground-motion record selection that informs the response calculation. The more accurate structure-and-site-specific non-ergodic risk estimates show that traditional ones may be biased in a way impossible to predict a priori. Hence, the use of the non-ergodic approach is recommended, whenever possible. However, further advancements of non-ergodic GMPEs are necessary before being routinely utilized in real-life risk assessment applications.
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    Regional Calibration of Hybrid Ground-Motion Simulations in Moderate Seismicity Areas: Application to the Upper Rhine Graben (2021)
    In:  Bulletin of the Seismological Society of America
    Details
    Publication Date: 2024-01-30
    Description: This study presents the coupling of the spectral decomposition results for anelastic attenuation, stress drop, and site effects with the Graves-Pitarka (GP) hybrid ground-motion simulation methodology, as implemented on the Southern California Earthquake Center (SCEC) broadband platform (BBP). It is targeted to applications in the Upper Rhine graben (URG), which is among the seismically active areas in western Europe, yet a moderate seismicity area. Our development consists of three main steps: (1) calibration of regional highfrequency (HF) attenuation properties; (2) modification of the hybrid approach to add compressional waves in the HF computation and examine various strategies to evaluate site amplification factors in the Fourier domain (e.g., VS30-based or site-specific factors); (3) testing of the simulations using earthquake records from the URG (3:7 〈 Mw 〈 5). The validation process of the simulated time histories is performed first on rock sites, and, then subsequently at all stations, whatever their site conditions. The performance of the simulations for rock sites is assessed through the standard validation technique in the BBP (comparison of the waveforms, intensity measures, and estimation of the response spectra model bias). We additionally compare the Fourier amplitude spectrum of the simulations and observations, and compute their corresponding bias. The results show that the simulated ground motions match the general characteristics of the recorded motions, and that the model bias generally fluctuates around zero across the broadband frequency range. Hence, the hybrid ground-motion methodology implemented in the SCEC BBP can be successfully applied outside high-seismicity areas and outside those areas for which it had been generally calibrated. Our results also show that HF modification and calibration were necessary to improve the fits with the observation, and demonstrate the potential benefits of using site-specific amplification factors compared to VS30-based amplification factors.
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    Chemical and boron isotope composition of tourmaline from pegmatites and their host rocks, Sierra de San Luis, Argentina (2021)
    In:  Canadian Mineralogist
    Details
    Publication Date: 2023-12-11
    Description: We report chemical and B-isotope analyses of tourmaline from Ordovician S-type granites, an aplite, LCT-type (lithium-cesium-tantalum) pegmatites, and metamorphic rocks of the Conlara Metamorphic Complex (CMC) in Sierra de San Luis, Argentina. For comparison, tourmaline from three LCT pegmatites in the adjacent Pringles Metamorphic Complex was also studied. Metamorphic tourmaline from the CMC has intermediate schorl–dravite compositions, with variable Fe# [100 * Fe/(Fe + Mg)] from 32 to 79. The δ11B values range from –14.8 to –8.9‰, which are typical values for continental metasediments and granites, ruling out a marine origin for the tourmalinite protoliths. Tourmaline from the S-type granites and aplite is more homogeneous, with Fe# from 48 to 60. The δ11B range (–14 to –9.8‰) of granitic tourmaline is within that of the metamorphic tourmaline, supporting the idea of boron recycling in the CMC during partial melting to form the granites. Tourmaline from CMC-hosted pegmatites is compositionally diverse and we distinguished three groups based on Fe#: Group 1: 42 to 50, Group 2: 50 to 62, and Group 3: 62 to 93. Regardless of strong variations in Fe#, tourmaline from all pegmatites in the CMC has δ11B values from –10.3 to –7.8‰. These values overlap with the range of related granites but are about 2 permil higher, which we attribute to crystallization of 10B-enriched minerals (mica and tourmaline) in the evolved magma from which the pegmatites formed. Pegmatites from the Pringles Metamorphic Complex contain tourmaline with a similar overall range of Fe# (45 to 84) as in the CMC but lower δ11B values (–13.2 to –11.2‰).
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    A multisource approach helps to detect a forest as a reference site in an intensively used rural landscape (Uckermark, NE Germany) (2021)
    In:  IForest-Biogeosciences and Forestry
    Details
    Publication Date: 2023-12-18
    Description: Background The sharp decline in near-natural areas worldwide is undisputed, but the consequences of this decline, apart from the loss of biodiversity, cannot be fully assessed. Biotic components of a landscape are usually more easily assessed than the abiotic components, since biotic components are often more easily detectable. A forest of (semi)natural stocking was selected in the northeastern part of Brandenburg (northeast Germany) to check whether it can serve as reference site for near-natural conditions or not. Analyses of archival sources and historic maps as well as field investigations were combined to reconstruct the dynamics of vegetation and soil as far back in time as possible. Results Palynological data from nearby sites provide evidence that the investigated area has been forested for several thousands of years and has hardly been structurally influenced by humans in the last 450 years. This evidence together with historical maps of tree species composition allows us to infer that the specific forest has been very close to a natural state for at least 250 years. Soil investigations support this conclusion, since a soil inventory, field studies on two catenas and corings at selected depressions rarely show signs of anthropogenic erosion and related colluviation. Parts of the area were cleared in prehistory, but near-natural soils have been preserved in other parts. Conclusions The area with these undisturbed parts is regarded as an ideal reference site. With this study, we show that using a multi-source approach it is possible to find potential reference sites and that such an approach is applicable in other regions. KEYWORDS ancient forest, geo-bioarchives, historic maps, land use legacy, pollen analysis, refer
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    Diamond formation in an electric field under deep Earth conditions (2021)
    In:  Science Advances
    Details
    Publication Date: 2023-12-18
    Description: Most natural diamonds are formed in Earth’s lithospheric mantle; however, the exact mechanisms behind their genesis remain debated. Given the occurrence of electrochemical processes in Earth’s mantle and the high electrical conductivity of mantle melts and fluids, we have developed a model whereby localized electric fields play a central role in diamond formation. Here, we experimentally demonstrate a diamond crystallization mechanism that operates under lithospheric mantle pressure-temperature conditions (6.3 and 7.5 gigapascals; 1300° to 1600°C) through the action of an electric potential applied across carbonate or carbonate-silicate melts. In this process, the carbonate-rich melt acts as both the carbon source and the crystallization medium for diamond, which forms in assemblage with mantle minerals near the cathode. Our results clearly demonstrate that electric fields should be considered a key additional factor influencing diamond crystallization, mantle mineral–forming processes, carbon isotope fractionation, and the global carbon cycle.
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    Accessing European Strong-Motion Data: An Update on ORFEUS Coordinated Services (2021)
    In:  Seismological Research Letters
    Details
    Publication Date: 2023-09-22
    Description: Strong groundmotion records and free open access to strong-motion data repositories are fundamental inputs to seismology, engineering seismology, soil dynamics, and earthquake engineering science and practice. This article presents the current status and outlook of the Observatories and Research Facilities for European Seismology (ORFEUS) coordinated strong-motion seismology services, namely the rapid raw strong-motion (RRSM) and the engineering strong-motion (ESM) databases and associated web interfaces andwebservices.We compare and discuss the role and use of these two systems using theMw 6.5 Norcia (Central Italy) earthquake that occurred on 30 October 2016 as an example of a well-recorded earthquake that triggered major interest in the seismological and earthquake engineering communities. The RRSM is a fully automated system for rapid dissemination of earthquake shaking information, whereas the ESM provides qualitychecked, manually processed waveforms and reviewed earthquake information. The RRSM uses only data from the European Integrated Waveform Data Archive, whereas the ESM also includes offline data from other sources, such as the ITalian ACcelerometric Archive (ITACA). Advanced software tools are also included in the ESM to allow users to process strong-motion data and to select ground-motion waveform sets for seismic structural analyses. The RRSM and ESM are complementary services designed for a variety of possible stakeholders, ranging fromscientists to the educated general public. The RRSM and ESM are developed, organized, and reviewed by selected members of the seismological community in Europe, including strong-motion data providers and expert users. Global access and usage of the data is encouraged. The ESM is presently the reference database for harmonized seismic hazard and risk studies in Europe. ORFEUS strong-motion data are open, “Findable, Accessible, Interoperable, and Reusable,” and accompanied by licensing information. The users are encouraged to properly cite the data providers, using the digital object identifiers of the seismic networks.
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    Seismic site response estimation for microzonation studies promoting the resilience of urban centers (2021)
    In:  Engineering Geology
    Details
    Publication Date: 2023-09-22
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    Volcanic Tremor Extraction and Earthquake Detection Using Music Information Retrieval Algorithms (2021)
    In:  Seismological Research Letters
    Details
    Publication Date: 2023-09-22
    Description: Volcanic tremor signals are usually observed before or during volcanic eruptions andmust be monitored to evaluate the volcanic activity. A challenge in studying seismic signals of volcanic origin is the coexistence of transient signal swarms and long-lasting volcanic tremor signals. Separating transient events fromvolcanic tremors can, therefore, contribute to improving upon our understanding of the underlying physical processes. Exploiting the idea of harmonic–percussive separation in musical signal processing, we develop a method to extract the harmonic volcanic tremor signals and to detect transient events from seismic recordings. Based on the similarity properties of spectrogram frames in the time–frequency domain, we decompose the signal into two separate spectrograms representing repeating (harmonic) and nonrepeating (transient) patterns, which correspond to volcanic tremor signals and earthquake signals, respectively. We reconstruct the harmonic tremor signal in the time domain from the complex spectrogram of the repeating pattern by only considering the phase components for the frequency range in which the tremor amplitude spectrum is significantly contributing to the energy of the signal. The reconstructed signal is, therefore, clean tremor signal without transient events. Furthermore, we derive a characteristic function suitable for the detection of transient events (e.g., earthquakes) by integrating amplitudes of the nonrepeating spectrogram over frequency at each time frame. Considering transient events like earthquakes, 78% of the events are detected for signal-to-noise ratio = 0.1 in our semisynthetic tests. In addition, we compared the number of detected earthquakes using our method for one month of continuous data recorded during the Holuhraun 2014–2015 eruption in Iceland with the bulletin presented in Ágústsdóttir et al. (2019). Our single station event detection algorithm identified 84% of the bulletin events. Moreover, we detected a total of 12,619 events, which is more than twice the number of the bulletin events.
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    Impact-related crystallization and modification of small zircons in Apollo 15 and 16 impactites at 4.2 Ga (2021)
    In:  Earth and Planetary Science Letters
    Details
    Publication Date: 2023-10-05
    Description: Because of their robustness against resetting, in situU-Pb ages of zircons in lunar impactites have the potential to provide constraints on the lunar bombardment history that may complement the more common K-Ar ages. Most previous work has focused on relatively large zircons that show growth zoning and ages were mostly interpreted as early igneous crystallization ages. Here we combine high-resolution mineralogical imaging and in situU-Pb dating by ion microprobe to identify, characterize and date 〈20μm size zircons in thin sections of lunar impact breccias. Several tens of grains of zircons of this size range were identified in thin sections of impactites from the Apollo 15 and 16 landing sites. Small zircons are more abundant in both noritic and evolved clinopyroxene, SiO2or K-feldspar bearing lithologies compared to anorthositic bulk compositions. Both granular zircon aggregates and overgrowth on existing zircon or baddeleyite (in breccias 15455 and 67915) are interpreted to reflect high-temperature recrystallization of zircons or its high-temperature-pressure precursor phases, following shock heating events by impact. In contrast, conchoidal or poikilitic zircons 〈10μm in Fe-Ni metal bearing noritic clasts or matrix (67915, 67955) crystallized in situfrom impact melt. Most U-Pb ages of the 24 analyzed grains are either concordant or reverse discordant with 207Pb-206Pb ages ranging from 4.15 to 4.25 Ga. The small age range, combined with a large textural spectrum and the frequent presence of Fe-Ni metal suggest zircon crystallization from impact melt and recrystallization of pre-existing zirconium-bearing minerals by impact heating. Such ‘impact’ zircons with 4.2 Ga ages have now been reported from most Apollo landing sites, suggesting widespread formation and modification of zircons by basin-forming impacts at this time. The contrast between U-Pb zircon (predominantly 4.2 Ga) and K-Ar feldspar ages (predominantly 3.9 Ga) likely reflects resetting of the latter chronometer by impact heating.
    Language: English
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    Stress Drop Derived from Spectral Analysis Considering the Hypocentral Depth in the Attenuation Model: Application to the Ridgecrest Region, California (2021)
    In:  Bulletin of the Seismological Society of America
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    Publication Date: 2024-01-25
    Description: We investigate the impact of considering a depth-dependent attenuation model on source parameters assessed through a spectral decomposition. In particular, we evaluate the effect of considering the hypocentral depth as an additional variable for the attenuation model, using as the target the tendency of the average stress drop to increase with depth, as observed in recent studies. Weanalyze the Fourier spectra of S-wave windows for about 1900 earthquakes with a magnitude above 2.5 recorded in the Ridgecrest region, southern California. Two different parameterizations of the attenuation term are implemented in the spectral decomposition, either as a function of the hypocentral distance alone or as a function of both epicentral distance and depth. The comparison of the spectral attenuation curves shows that, although the hypocentral model describes, on average, the range of values spanned by the attenuation curve for different depths, systematic differences with distance, depth, and frequency are observed. These differences are transferred to the source spectra and, in turn, to the source parameters extracted from the best-fitting ω−2 models. In particular, stress drops for events deeper than 7 km are, on average, almost double even when depth is introduced explicitly in the attenuation model. The increase of stress drop with depth is confirmed also after accounting for the increase of the shear velocity with depth, which absorbs about 30%–40% of the total increase. Moreover, a qualitative comparison with a model for the gradient of the effective normal stress confirms the reliability of the observed trend. Finally, the coherent spatial patterns shown by a simplified 2D tomographic representation of the spectral residuals highlights the impact on ground-shaking variability of the lateral variability of the crustal attenuation properties in the region.
    Language: English
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    An open-source site database of strong-motion stations in Japan: K-NET and KiK-net (v1.0.0) (2021)
    In:  Earthquake Spectra
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    Publication Date: 2024-01-25
    Description: This article describes an open-source site database for a total number of 1742 earthquake recording sites in the K-NET (Kyoshin network) and KiK-net (Kiban Kyoshin network) networks in Japan. This database contains site characterization parameters directly derived from available velocity profiles, including average wave velocities, bedrock depths, and velocity contrast. Meanwhile, it also consists of earthquake horizontal-to-vertical spectral ratio (HVSR) and peak parameters, for example, peak frequency, amplitude, width, and prominence. In addition, the site database also comprises topographic and geological proxies inferred from regional models or maps. Each parameter is derived in a consistent manner for all sites. This site database can benefit the application of machine learning techniques in studies on site amplification. Besides, it can facilitate, for instances, the search of the optimal site parameter(s) for the prediction of site amplification, the development and testing of ground-motion models or methodologies, as well as investigations on spatial or regional variability in site response. All resources (the site database, earthquake HVSR data at all sites, and the MATLAB script for peak identification) can be freely accessed via: https://doi.org/10.5880/GFZ.2.1.2020.006
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    Exploring the Dimensionality of Ground-Motion Data by Applying Autoencoder Techniques (2021)
    In:  Bulletin of the Seismological Society of America
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    Publication Date: 2024-01-25
    Description: In this article, we address the question of how observed ground-motion data can most effectively be modeled for engineering seismological purposes. Toward this goal, we use a data-driven method, based on a deep-learning autoencoder with a variable number of nodes in the bottleneck layer, to determine how many parameters are needed to reconstruct synthetic and observed ground-motion data in terms of their median values and scatter. The reconstruction error as a function of the number of nodes in the bottleneck is used as an indicator of the underlying dimensionality of ground-motion data, that is, the minimum number of predictor variables needed in a ground-motion model. Two synthetic and one observed datasets are studied to prove the performance of the proposed method. We find that mapping ground-motion data to a 2D manifold primarily captures magnitude and distance information and is suited for an approximate data reconstruction. The data reconstruction improves with an increasing number of bottleneck nodes of up to three and four, but it saturates if more nodes are added to the bottleneck.
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    Geological controls on geothermal resources for power generation (2021)
    In:  Nature Reviews Earth & Environment
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    Publication Date: 2024-01-25
    Description: Threats posed by the climate crisis have created an urgent need for sustainable green energy. Geothermal resources have the potential to provide up to 150 GWe of sustainable energy by 2050. However, the key challenge in successfully locating and drilling geothermal wells is to understand how the heterogeneous structure of the subsurface controls the existence of exploitable fluid reservoirs. In this Review, we discuss how key geological factors contribute to the profitable utilization of intermediate-temperature to high-temperature geothermal resources for power generation. The main driver of geothermal activity is elevated crustal heat flow, which is focused in regions of active magmatism and/or crustal thinning. Permeable structures such as faults exercise a primary control on local fluid flow patterns, with most upflow zones residing in complex fault interaction zones. Major risks in geothermal resource assessment and operation include locating sufficient permeability for fluid extraction, in addition to declining reservoir pressure and the potential of induced seismicity. Advanced computational methods permit effective integration of multiple datasets and, thus, can reduce potential risks. Future innovations involve engineered geothermal systems as well as supercritical and offshore geothermal resources, which could greatly expand the global application of geothermal energy but require detailed knowledge of the respective geological conditions.
    Language: English
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    The interplay of a fault zone and a volcanic reservoir from 3D elasto-plastic models: Rheological conditions for mutual trigger based on a field case from the Andean Southern Volcanic Zone (2021)
    In:  Journal of Volcanology and Geothermal Research
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    Publication Date: 2024-01-25
    Description: The Southern Andes margin hosts active and fossil volcanic, geothermal, and mineralized systems documenting intense geofluid migration through the crust. Fluid flow is also spatially associated with crustal faults that accommodate the bulk deformation arising from oblique plate convergence. Although recognized, the precise local mechanical interaction between faults and crustal reservoirs is yet to be better understood. Here we present 3D numerical models of a magmatic reservoir and a fault zone set about 4 km apart, inspired by the Tatara-San Pedro volcanic complex in the Southern Volcanic Zone (~36°S), which displays a geothermal field and a margin-parallel dextral active fault zone constrained by published magnetotelluric profiles and crustal seismicity respectively. We investigate elasto-plastic deformation and stress patterns in the intermediate bedrock space between the reservoir and the fault zone and test how shear stress, volumetric strain, and plastic strain develop. We also test the potential of enabling brittle failure of their counterpart by imposing either (1) a strike-slip displacement along the fault zone, or (2) a magmatic overpressure at the cavity walls. Parametric tests of Young's modulus and frictional strength provide the conditions for macro-scale brittle failure and show the development of diffuse domains of dilational strain of the order of 10−5 –10−3 in the intervening bedrock. This dilation is a proxy to the opening of voids or volumetric cracking in the bedrock, which tends to increase porosity and permeability allowing over-pressurized geofluids to migrate within these domains. Our results show that a minimum of 60 m of fault displacement is required to trigger brittle failure of an upper crustal cavity if the bedrock is stiff, whereas, for a more compliant bedrock, more than 100 m of localized slip motion is required. This implies that it is rather the accumulated effect of repeated crustal fault displacement that potentially favors fluid pathways upwards, rather than a single seismic event. On the other hand, a minimum of 7.5 MPa of fluid overpressure is required for a mid-crustal cavity (15 km depth) to trigger brittle failure of the fault zone. This threshold overpressure increases up to 50 MPa when the cavity is shallower (6 km depth). Our results show that in general, shallow reservoirs must be very close to fault zones (less than 1–2 km apart) to reactivate them. The models show that localized strike-slip tectonics and magma intrusions build a dilational stress field at the scale of several kilometers, that promotes fluid pathways to the surface. Further combining this interaction with the regional transpressional stress field may explain observations of transient fluid pathways on seemingly independent timescales along the Andean margin.
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