ALBERT

Description: The ability of any satellite gravity mission concept to monitor mass transport processes in the Earth system is typically tested well ahead of its implementation by means of various simulation studies. Those studies often extend from the simulation of realistic orbits and instrumental data all the way down to the retrieval of global gravity field solution time-series. Basic requirement for all these simulations are realistic representations of the spatio-temporal mass variability in the different sub-systems of the Earth, as a source model for the orbit computations. For such simulations, a suitable source model is required to represent (i) high-frequency (i.e., subdaily to weekly) mass variability in the atmosphere and oceans, in order to realistically include the effects of temporal aliasing due to non-tidal high-frequency mass variability into the retrieved gravity fields. In parallel, (ii) low-frequency (i.e., monthly to interannual) variability needs to be modelled with realistic amplitudes, particularly at small spatial scales, in order to assess to what extent a new mission concept might provide further insight into physical processes currently not observable. The new source model documented here attempts to fulfil both requirements: Based on ECMWF’s recent atmospheric reanalysis ERA-Interim and corresponding simulations from numerical models of the other Earth system components, it offers spherical harmonic coefficients of the time-variable global gravity field due to mass variability in atmosphere, oceans, the terrestrial hydrosphere including the ice-sheets and glaciers, as well as the solid Earth. Simulated features range from sub-daily to multiyear periods with a spatial resolution of spherical harmonics degree and order 180 over a period of 12 years. In addition to the source model, a de-aliasing model for atmospheric and oceanic high-frequency variability with augmented systematic and random noise is required for a realistic simulation of the gravity field retrieval process, whose necessary error characteristics are discussed. The documentation of the updated ESA Earth System Model (updated ESM) for gravity mission simulation studies is organized as follows: The characteristics of the updated ESM along with some basic validation is presented in Volume 1. A detailed comparison to the original ESA ESM (Gruber et al., 2011) is provided in Volume 2, while Volume 3 contains the description of a strategy to derive realistic errors for the de-aliasing model of high-frequency mass variability in atmosphere and ocean.

Description: The integrated plate boundary in Chile (IPOC) combines 15 broadband stations with strong-motion sensors, GPS, strain sensors and magneto-telluric stations. The Chilean subduction zone setting provides a high background rate of seismicity (crustal, intermediate depth, and plate interface) in a region with exceptionally low ambient noise, particularly at higher frequencies. We have deployed seismic mini-arrays in the vicinity of IPOC stations PB02 and PB07, and installed a third array to the east of these stations near the village of Quillagua, such that all three arrays form a triangle. Each array has 10 elements and an aperture in the km range. The study area lies just to the north of the northern boundary of the rupture area of the Tocopilla earthquake of 2007 Mw=7.7) and just above or slightly to the east of the downdip limit of plate interface seismicity. Installing the mini-arrays in the area of the existing IPOC has the following advantages: • Independent knowledge of background structure and seismicity from existing and ongoing studies. • Should any transients or other unusual signals be found in the array data, we can look for anomalous signals in geodetic and MT recordings, which will help to narrow down possible underlying mechanisms.

Description: The 9th TRACE conference (Tree Rings in Archaeology, Climatology and Ecology) was organized by the Institute for Forest Growth, University of Freiburg, on April 22nd – 25th 2010 in Freiburg, Germany. [...] This volume of TRACE Proceedings contains 26 short papers and gives an overview of the wide spectrum of fields in tree-ring research.

Description: Passive continental margins offer the unique opportunity to study the processes involved in continental extension and break up as well as the role of hot-spot related magmatism. We conducted combined on- and offshore seismic experiments in Northern Namibia designed to characterize the Southern African passive margin at the interaction with the Walvis Ridge, to assess the interaction of the presumed plume with continental lithosphere and to determine the deep structure of the transition from the coastal fold belt to the stable craton, where the Walvis Ridge hits the African continent. The seismic project integrated three experiments, (A) an onshore, coast-parallel refraction seismic profile, (B) two onshore-offshore wide-angle seismic transects, and (C) a combined on- and offshore seismic experiment to image the sub-Moho velocity (Pn tomography) at the ocean-continent transition (Fig. 1). The knowledge of the lithospheric structure of the margin together with results from other geoscientific studies (e.g., conducted within the SPPSAMPLE, DFG Priority Program 1375, South Atlantic Margin Processes and Links with onshore Evolution) will help to address fundamental questions such as, how continental crust and plume head interact, what the extent and volumes of magmatic underplating is, and how and which inherited (continental) structures might have been involved and utilized in the break-up process.

Description: This thesis summarizes the results of the WSM project’s second phase (1996‐2008). In particular it presents the major achievements that have been accomplished with the WSM 2008 database release that has been compiled under the guidance of the author. Furthermore, the thesis briefly presents three of the author’s numerical models that aim at quantification the temporal changes of the crustal stress field.

Description: This publication is a result of the 12th TRACE conference (Tree Rings in Archaeology, Climatology and Ecology) organized by the Department of Agriculture, Forests, Nature and Energy (DAFNE) of the Università della Tuscia (Viterbo, Italy) on May 08th – 11th 2013 in Viterbo, Italy. [...] A total of 20 manuscripts were submitted. After review 19 short papers are published in this volume, giving an overview of the wide spectrum of fields in tree-ring research.

Description: [...] In context of this work, a new damage mechanism is proposed: the mechanically induced fracture face skin. This new mechanism results from mechanical interactions between the proppants and the reservoir rock, due to the increasing stress on the rock-proppant system during production. Proppant embedment into the fracture face and proppant crushing leads to fines production and can impair the fracture performance. In order to achieve sustainable, longterm productivity from a reservoir, it is indispensable to understand the hydraulic and mechanical interactions in the rock-proppant system. In order to analyse the hydraulic and mechanical interactions, laboratory experiments using three different flow cells were conducted. These flow cells were used to localise and quantify the mechanical damage at the fracture face, as well as to investigate the long-term stability of a rock-proppant system under in-situ reservoir conditions. [...]

Description: This short report describes the first attempt at obtaining a preliminary cross-border risk model for Central Asia starting from datasets that were already available at the beginning of the EMCA Project.

Description: The ability of any satellite gravity mission concept to monitor mass transport processes in the Earth system is typically tested well ahead of its implementation by means of various simulation studies. Those studies often extend from the simulation of realistic orbits and instrumental data all the way down to the retrieval of global gravity field solution time-series. Basic requirement for all these simulations are realistic representations of the spatio-temporal mass variability in the different sub-systems of the Earth, as a source model for the orbit computations. For such simulations, a suitable source model is required to represent (i) high-frequency (i.e., sub-daily to weekly) mass variability in the atmosphere and oceans, in order to realistically include the effects of temporal aliasing due to non-tidal high-frequency mass variability into the retrieved gravity fields. In parallel, (ii) low-frequency (i.e., monthly to interannual) variability needs to be modelled with realistic amplitudes, particularly at small spatial scales, in order to assess to what extent a new mission concept might provide further insight into physical processes currently not observable. The new source model documented here attempts to fulfil both requirements: Based on ECMWF’s recent atmospheric reanalysis ERA-Interim and corresponding simulations from numerical models of the other Earth system components, it offers spherical harmonic coefficients of the time-variable global gravity field due to mass variability in atmosphere, oceans, the terrestrial hydrosphere including the ice-sheets and glaciers, as well as the solid Earth. Simulated features range from sub-daily to multiyear periods with a spatial resolution of spherical harmonics degree and order 180 over a period of 12 years. In addition to the source model, a de-aliasing model for atmospheric and oceanic high-frequency variability with augmented systematic and random noise is required for a realistic simulation of the gravity field retrieval process, whose necessary error characteristics are discussed. The documentation is organized as follows: The characteristics of the updated ESM along with some basic validation are presented in Volume 1 of this report (Dobslaw et al., 2014). A detailed comparison to the original ESA ESM (Gruber et al., 2011) is provided in Volume 2 (Bergmann-Wolf et al., 2014), while Volume 3 (Forootan et al., 2014) contains a description of the strategy to derive a realistically noisy de-aliasing model for the high-frequency mass variability in atmosphere and oceans. The files of the updated ESA Earth System Model for gravity mission simulation studies are accessible at DOI:10.5880/GFZ.1.3.2014.001.

Description: The magnetic field of the Earth varies in space and time. Geomagnetism as research area that aims to describe and understand the sources of these variations is supported by two pillars: first, regular high-precision measurements in the global network of magnetic observatories and repeat stations are necessary to register the field and its variations at all. Second, mathematical methods are required in order to extract magnetic field models from this large data set. Methods applied to data offer insights in the mechanisms generating the magnetic field. This thesis covers both subjects. In a first part, following the description of the state of the art in observatory instrumentation, I explain in detail two instruments that have the potential to streamline the classical procedures: The Geomagnetic AUtomated SyStem GAUSS paves the way to automated absolute measurements, up to now only possible manually. The newly developed DI3 technique improves and simplies the standard manual measurements signicantly and thus reduces the requirements placed on observers. The second part deals with the mathematical tools available for geomagnetic field modelling. I focus on harmonic splines that can be derived from the classical approach of spherical harmonics. These base functions are interpolatory and have a localised shape while satisfying Laplaces equation. Hence, they are applicable to fit data regionally or globally. The harmonic splines are used with a data set made of repeat station and observatory measurements from Southern Africa. This region is of special interest because the field intensity is very low and and both spatial and temporal field gradients exist. Subdivided into an analysis of ancient (years 1961-2001) and recent (2005-2009) data, two continuous regional field models SAMS and X-SAMS are derived. From the analysis of the field models, a better understanding of the field behaviour is gained. Finally, the harmonic splines are used in a case study on globally distributed secular variation data. Rotating the data set in a system of coordinates aligned with the dipole axis and modelling it with the harmonic splines reveals the external origin of observed fast variations.

Description: [...] In this thesis, data from seismic and infrasound stations were analyzed in order to see effects of tsunamis of the great Sumatra-Andaman 2004 and Tohuku-Oki 2011 earthquakes. Data used are from seismic stations of the Global Seismic Network (GSN) around the Indian and Pacific oceans and from infrasound stations of the International Monitoring System of the Comprehensive Test Ban Treaty Organization (IMS/CTBTO). In both data sets, seismic and infrasound, tsunami signals are observed in the period range of 500to2000s. These data may add to two new very useful observables for tsunami early warning systems. [...]

Description: Beneath the Pamir and Hindu Kush mountains an earthquake zone is observed in 80 to 300 km depth. It resembles in form and intensity the intermediate depth seismicity in subduction zones, here lithosphere is recycled in the Earth’s mantle. The fundamental tectonic concept of subduction is well established for convergent margins including an oceanic plate. The Pamir, however, is situated in an intra-continental setting and is formed during a continent-continent collision. This thesis aims to contribute to the investigation of the active tectonic process underlying the local occurrence of the seismicity in upper mantle depths. The field experiment for this study was performed in the framework of the multidisciplinary TIPAGE project from 2008 to 2010 and included large parts of the Pamir, the adjacent Tajik Depression and the Southern Tien Shan. The receiver function technique was applied to detect and locate seismic discontinuities in the subsurface in order to perform seismic imaging. The results clearly attest to an intra-continental subduction. Beneath the Pamir, the subducting plate is of Eurasian provenance. A southerly dipping 10 to 15 km thick low velocity zone could be resolved along a north-south profile in the eastern Pamir framing the earthquake zone in the upper mantle. This low velocity zone appears to be connected to the lower crust north of the seismic zone indicating subduction of crustal material in north to south direction. West of this north-south profile the zone of intermediate depth seismicity describes an arc changing its strike from east-west beneath the eastern Pamir to north-south beneath the western Pamir. Thereby the dipping direction of the slab changes from due south to due east. The geometry of this slab is confirmed by various receiver function cross sections. Towards western direction the subducted slab is connected to the crust of the Tajik Depression, indicating that the slab is the western extension of the Tajik Depression plate. Since the crustal thickness of the Tajik Depression is determined to at least 40 km, a continental composition for the crust of the Tajik Depression is inferred even though its underlying mantle lithosphere appears to be thin. The crustal thickness is mapped for the whole region. The resulting Moho map shows a 65 to 75 km thick crust in the Pamir and a 40 to 45 km thick crust in the surrounding basins. The arcuate subduction of the Tajik Depression plate and its eastern extension is reflected by characteristic Moho depth anomalies along the arc.

Description: The present work tries to condense the state‐of‐the‐art for the exploration and exploitation of geothermal energy. Although a lot of experiences from different sites worldwide are integrated in this study, some sections do reflect the German experience. For example, the German Renewable Energy Sources Act (EEG, see page 78) enables also a specific promotion and growth of the geothermal sector in Germany by guaranteeing special feed‐in tariffs for a 20‐years period. During the last years, several countries worldwide have introduced similar renewable energy promotion policies (some of them restricted to certain energy sources only or requiring a certain renewable energy quote), supporting investigations also in geothermal applications. Thus, the experiences in Germany may be of some value. Dependent on the political‐economical framework, the geothermal exploration and exploitation of deeper reservoirs represents an excellent option to extend geothermal applications also in areas where shallow geothermal reservoirs may not be able to match the local energy demand. Therefore, also challenges related to the exploration and exploitation of deep low‐permeability reservoirs are included in this study.

Description: This Scientific Technical Report presents two so-called “Reference reports” produced during the MATRIX project. These reports were provided to the European Commission asdeliverables, namely D8.4 “MATRIX Results I and Reference Report” and D8.5 “MATRIX Results II and Reference Report”. D8.4 presented a series of specific reports outlining theresults of the project, written in a manner accessible not only to the specialist but with a broader audience in mind. D8.5 deals with the risk governance within a multi-hazard and risk context and has since been published. We therefore divide with document in two, where part1 represented the outcomes presented in D8.4 while D8.5 forms part 2.

Description: [...] In order to construct the 3D structural model of the Norwegian continental margin, all mentioned datasets were compiled and gridded separately for each layer. The gridded data were merged into the 3D structural model and, therefore, all obtained thickness maps and structural depth maps are spatially consistent in 3D.

Description: An integrated geological and geophysical approach was applied to comprehend the tectonic setting and seismic structure of the North Tapanuli district (North Sumatra Indonesia) where several geothermal manifestations are located. For the first time, passive seismic methods are used as a geothermal exploration tool in Indonesia. The specific aims of the seismological study are to provide Vp, Vp/Vs, and seismic attenuation images as well as the detailed fault structure of the region derived from seismicity and focal mechanism analysis. A seismic network of 42 short period instruments was installed in the region covering the Tarutung (in the north) and the Sarulla basin (in the south) for 10 months starting from May 2011. The seismic arrivals were detected by using an optimized automatic earthquake detection approach. The earthquakes were then localized by using HYPO71 with a 1D velocity model. In order to increase the picking accuracy, the seismic onsets were revised manually and the earthquakes were relocated by using the same procedure.

Description: Megacities as challenge for interdisciplinary research: the "Risk Habitat Megacity" research initiative / Dirk Heinrichs, Kerstin Krellenberg. - Mega-urban societies at risk / Frauke Kraas, Carsten Butsch. - Megacity Istanbul: earthquake risk and early warning in a megacity / Stefano Parolai, Jochen Zschau, Claus Milkereit, Matteo Picozzi, Angelo Strollo. - Neapel in der Zange / Thomas Walter

Description: The theme of this thesis is to investigate the sensitivity of several different formations of future satellite gravity missions. The work has three main aspects. The first, and the most important, is the development and testing of a global directional wavelet transformation as a mathematical tool to analyse sensitivity of satellite gravity mission. This is done by propagating full covariance matrices w.r.t. the spherical harmonics functions onto the directional wavelet transform. For the first time, we are able to accurately quantify the stripes that are typical for the error pattern of the GRACE gravity mission. The second aspect is the simulation of a satellite gravity formation, in order to achieve accuracy information in the form of a full covariance matrix. The third aspect involves analyzing results from the GRACE mission, which is already in orbit and has been delivering data since 2002. We compare the simulations of GRACE to the data delivered by the GRACE mission. This way, we are able to establish a relationship between the simulations and real-life data and evaluate the quality of the simulations.