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: 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 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: 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: 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: 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: 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: The striking improvements in long- to medium-wavelengths gravity field recovery achieved with GPS-CHAMP and GPS-GRACE high-low and GRACE K-band range low-low satellite-to-satellite tracking prompted us to combine the satellite data with surface data from altimetry over the oceans and gravimetry over the continents to generate a new, high resolution global gravity field model: EIGEN-CG01C. The model is complete to degree/order 360 in terms of spherical harmonics and resolves half-wavelengths of 55 km in the geoid and gravity anomaly fields. A special band-limited combination method has been applied in order to preserve the high accuracy from the satellite data in the lower frequency band of the geopotential and to allow for a smooth transition to the high-frequency band, dominated by the surface data. Compared to pre-CHAMP/GRACE global high-resolution gravity field models, the accuracy was improved by one order of magnitude to 4 cm and 0.5 mgal in terms of geoid heights and gravity anomalies, respectively, at a spatial resolution of 200 km half-wavelength. The overall accuracy at degree/order 360 is estimated to be 20 cm and 5 mgal, respectively, and benefits significantly from recently released new gravity anomaly compilations over the polar regions. In general, the accuracy over the oceans is better than over the continents reflecting the higher quality of the available surface data.

Description: This thesis focuses on the seismic structure of the lithosphere and upper mantle beneath the western Eger Rift area with the aim of investigating deep-lying possible causes of the phenomena observed at surface. For the investigation, data of the international passive seismic experiment BOHEMA carried out in 2002/2003 was used. The BOHEMA network consisted of 61 permanent and 84 temporary stations and was centred on the western Eger Rift. The resulting large data set allowed a high resolution P and S receiver function study using P-to-S and S-to-P converted waves, respectively, to map seismic discontinuities in the lithosphere and upper mantle. Data from an earlier passive seismic experiment was additionally used to complement the BOHEMA data set. The results of the analysis are described in this thesis ‘from top to bottom’. [...] Furthermore, the first map of average crustal vp/vs ratios is presented for the investigated area.

Description: In der vorliegenden Arbeit werden der Einfluss seismischer Anisotropie auf wahre oder scheinbar auftretende tensile Quellanteile untersucht und Erdbebenmechanismen unter Berücksichtigung seismischer Anisotropie bestimmt. Es wird gezeigt, dass der Momententensor und die Abstrahlmuster eines Scherbruches im anisotropen Medium denen eines tensilen Bruches im isotropen Medium ähneln können. Umgekehrt treten Ähnlichkeiten tensiler Beben in anisotropen Gesteinen mit Scherbrüchen in isotropen Medien auf. Damit existieren Mehrdeutigkeiten beobachteter tensiler Quellanteile. Die Effekte von Anisotropie hängen von der Orientierung des Bruches und vom Grad der Anisotropie ab. Außerdem beeinflusst Anisotropie das Moment eines Bebens. [...] Mit dieser Arbeit werden erstmals zeitliche und räumliche Veränderungen tensiler Quellanteile und Spannungszustände im Vogtland für Erdbeben im Jahr 2000 beob- achtet. Diese haben auch dann Bestand, wenn seismische Anisotropie berücksichtigt wird. Sie können durch Fluide erklärt werden, die in die Bruchflächen eindringen.

Description: Das Veranstaltungsthema „Innovation und Zukunft der Steine- und Erden-Industrie in Mitteleuropa“ wurde gewählt, um die seit 30 Jahren verpasste Gelegenheit ins Bewusstsein zu rufen, dass eine moderne Industrie heimische Rohstoffe benötigt. Wie sich aus den Einzelbeiträgen und den Tabellen entnehmen lässt, ist die Bundesrepublik Deutschland hinsichtlich der Steine und Erden ein rohstoffreiches Land und ein wesentlicher Wirtschaftsfaktor. Dieses Bewusstsein scheint bei der überbordenden ‚Ökologie’-diskussion erst seit kurzer Zeit in den Fokus zu geraten, wurde doch bei allen Diskussionen der Naturschutzgesetzgebung etc. fast völlig vergessen, dass Rohstoffabbau nur möglich ist, wenn Vorrang- oder Schutzzonen mindestens für die nächsten 50 Jahre ausgewiesen werden, wobei das eine Daueraufgabe in der Zeit ist. Diese Aufgabe ist eigentlich eine Hoheitsaufgabe und setzt auch die geologisch / bodenkundliche Basiskartierung der Bundesrepublik Deutschland auf neuesten Stand flächendeckend voraus, um flexibel mit neuen Konzepten auf neueste industrielle Herausforderungen antworten zu können. NEGENDANK (2005) hat einige statistische Daten zusammengetragen, aus denen die Bedeutung im Überblick hervorgeht (Tab. S. 3). Die hier vorgelegten Beiträge erlauben einen vertiefenden Einblick in die Situation der Steine- und Erdenindustrie, ihres Innovationspotentials sowie ihrer Zukunft.

Description: Based on the physical processes governing the motion and dynamics of poly-thermal ice sheets, we distinguish two regions; the cold region, where the ice temperature is below the melting point, and the temperate region, where the ice temperature is exactly equal to the melting point, leading to the presence of a water fraction. This work focuses on the analysis and description of the temperate zone on the basis of rational thermo-dynamics of reacting mixtures. The balance laws for the ice-water mixture, that is the mass balance, balance of linear and angular momenta, energy and entropy, are discussed. A physical model for a polythermal ice sheet is then established, including appropriate boundary and transition conditions. The resulting formulation is convenient for numerical implementation. Numerical examples are carried out for a stationary 2-D case and the results of the present and traditional formulations are compared.

Description: This work describes the results of seismological field campaigns and experiments using combined seismic networks of varying geometries such as a combined seismic downhole and surface network or a combined temporary local and permanent regional network. The networks were deployed in different tectonic environments, i.e. in a stable intraplate surrounding, at a plate boundary along a major transform fault zone and in forearc and backarc settings of a subduction zone to record different types of seismicity (induced earthquakes, aftershocks, subduction-related seismicity). Recording periods are typically several months. The basic ideas behind all the different experiments and studies presented here can be described as follows: In a first step, a state of the art seismic network is designed and deployed in a selected area to record local (micro)seismic activity at low magnitude detection threshold. The acquired data base is then evaluated using standard processing techniques to generate a proper hypocenter catalog for the area of investigation during the observational period. This period might be extended (at higher magnitude detection threshold) through re-evaluating and calibrating earlier hypocenter catalogs gained from records of regional permanent networks. This new catalog for the selected region then forms the base for further evaluation using different approaches one of which is the determination of fault plane solutions in order to determine the local stress field orientation and relate it to the WSM data or information on regional displacement fields determined from GPS recordings.

Description: Die tiefe Geothermie in Deutschland erschließt Reservoirs in 3 bis 5 km Tiefe mit Temperaturen von 100 °C bis 200°C. Für die Wandlung dieser Niedertemperaturwärme in elektrische Energie kommen voraussichtlich nur Kraftwerke mit Sekundärkreislauf in Frage. Die zwei zur Zeit verfügbaren Systeme, der Organic Rankine Cycle (ORC) und der Kalina-Prozess werden analysiert und bewertet. Die aus den Wasserdampfprozessen bekannten Methoden zur Verbesserung des Wirkungsgrades werden hinsichtlich ihrer Übertragbarkeit geprüft, alternative Möglichkeiten der Verbesserung untersucht und daraus praktikable Vorgehensweisen beim Entwurf der Prozesse entwickelt.

Description: A set of 59 seismological stations was deployed in the Central Andes region at 21°S (Chile-Bolivia) along a profile ~600 km long and were operated between 2002 and 2004. The teleseismic tomographic images (from P- and S- waves) show low-velocity anomalies that are interpreted as the effects of melting or fluids at both flanks of the Altiplano plateau. Beneath the Central Volcanic Zone (CVZ) a low-velocity anomaly is interpreted to be caused by fluids that are the origin of the volcanic material from the CVZ. A low-velocity anomaly in the upper crust is interpreted as the Altiplano Low-Velocity Zone that appears to extend as far to the east as the Eastern Cordillera. A high-velocity body between 100 km and 150 km depth is interpreted as being part of the old cold lithosphere that detached from the base of the crust. The Brazilian Shield is thought to be responsible for the strong high-velocity anomaly on the eastern side of the Central Andes. In addition, another set of 19 stations was deployed in the southern Argentine Puna along a profile ~200 km long and were run over the same period of time (2002-2004). The intention was to study the crustal thickness at 25.5°S, where delamination of the lithosphere was proposed to explain the higher elevation of the Puna plateau. Beneath the plateau a negative velocity anomaly is observed and interpreted here as being the location of fluid transfer between the deeper and shallower portions of the crust, that emanate from the Benioff zone at depths of ~200 km. This anomaly clearly divides in two branches: one to the west towards the volcanic arc (CVZ) and the other to the east where the back-arc volcanoes are located. On their way to lower depths, the fluid paths are probably influenced by the presence of nearby isotherms. The bifurcation of the ascending path could be related to the presence of the lithosphere-asthenosphere boundary (LAB) at ~100-130 km. Based on our observations, the type and form of the anomaly, it is possible to propose the presence of a return-flow type model for fluid ascent in contraposition to the assumed corner-flow model usually proposed for the Andes. The fluids that cause the seismic anomalies beneath the Puna plateau are generated at deeper levels in the asthenosphere and ascend parallel to the oceanic slab in the manner of a return-flow. In the crust and beneath the Salar de Antofalla (SA), a high-velocity block with seismic activity is interpreted as part of the old and cold Palaeozoic magmatic arc (Faja Eruptiva de la Puna Occidental). The presence of this block is may be responsible for the distribution of volcanic activity localized at both sides of this anomaly. Eastern of the SA, it is possible to recognize a zone with low-velocities beneath the Galan volcano. A sharp limit imposed by high velocities, probably related to metamorphic rocks from the Paleozoic basement (Tacuil and Luracatao ranges) can be detected on the east of the profile. A high-velocity block with seismic activity is located in the crust beneath the Salar de Antofalla (SA) and interpreted as part of the old and cold Palaeozoic magmatic arc (Faja Eruptiva de la Puna Occidental). This block might be responsible for the distribution of volcanic activity localized at both sides of this anomaly. Beneath the Galan volcano and east of the SA, a zone with low-velocities can be recognized. A sharp limit towards high-velocities can be observed on the east of the profile, probably related to metamorphic rocks from the Palaeozoic basement (Tacuil and Luracatao ranges).

Description: The purpose of this study is to refine the probabilistic seismic hazard assessment for Vanuatu. The analysis is complicated by inconsistencies of the global and local data for the investigated region and systematic inadequacies of the attenuation relation available. An additional aspect in the field of which more research would be desirable is the de-clustering algorithm for the identification of dependent earthquakes. In order to quantify the inevitable uncertainties associated with our results, we used a Logic Tree approach. The report is subdivided into seven chapters. Chapter 2 summarises the geology and tectonic setting of the Vanuatu island arc. Prior scientific investigations will be sketched briefly and to the degree to which they are relevant for our further considerations. The consecutive Chapter 3 describes the different data sources used for the calculations. Together, the local earthquake catalogue provided by the IRD (Institut de Recherche pour le D´eveloppement) and the global catalogues constitute a comprehensive data base for the region. The homogenisation of different catalogues required the conversion of magnitudes through maximum likelihood regressions. Chapter 4 gives a brief overview over the methodological concept applied. The implementation of the Cornell methodology involves two key steps: The first step is to construct a seismicity model (Chapter 5) including the definition of source zones and seismicity parameters characterising the level and type of activity in the respective zone. The second step is to determine an appropriate attenuation relation for the earthquake-generated ground motion in dependence of magnitude and distance. Chapter 6 compares several attenuation relations from the recent geophysical literature. We argue that the modeling of attenuation is the weakest link in this analysis and the major source of uncertainty. The new seismic hazard maps are presented and discussed in Chapter 7. The map that we consider to be the most relevant is also shown on the inner title page of this report. Our findings indicate that the seismic hazard in Vanuatu has been underestimated by prior assessments such as the Global Seismic Hazard Assessment Programme GSHAP (cf. Fig. 1.1).

Description: Die vorliegende Untersuchung befaßt sich mit dem Einfluß des durch die letzte pleistozänen Enteisung hervorgerufenen glazial-isostatischen Ausgleichs auf die rezente Meeresspiegeländerung. Diese Änderung kann sowohl durch Satellitenaltimetrie als auch durch Pegelmessungen bestimmt werden.

Description: Bivergent wedges result from the interaction between deformation, flexure and surface processes. Based on 2D sandbox simulations in conjunction with PIV, this study investigates the influence of these processes on the spatio-temporal evolution of strain-partitioning within, and the associated surface uplift of, bivergent wedges. To facilitate interpretation and to successfully communicate results, two new display types, i.e., the surface uplift and the evolution of deformation map are introduced.

Description: Following work is embedded in the multidisciplinary study DESERT (DEad SEa Rift Transect) that has been carried out in the Middle East since the beginning of the year 2000. It focuses on the structure of the southern Dead Sea Transform (DST), the transform plate boundary between Africa (Sinai) and the Arabian microplate. In this work a short description of the seismic reflection method and the various processing steps is followed by a geological interpretation of the seismic data, taking into account relevant information from other studies.

Description: This thesis work describes a new experimental method for the determination of Mode II (shear) fracture toughness, KIIC, of rock and compares the outcome to results from Mode I (tensile) fracture toughness, KIC, testing using the International Society of Rock Mechanics (ISRM) Chevron-Bend (CB-) method. The fracture toughness describes the resistance of rock to fracturing. This parameter is therefore important when estimating the failure of rock and rock structures using rock fracture mechanics principles.

Description: The main objective of this thesis is an investigation and description of the secular variation of the Earth's magnetic field between 1980 and 2000. In particular, in the first part of this study the phenomenon of geomagnetic jerks are investigated by means of a deterministic model, which basically gives a description of the secular variation as a parameterization of typical periodicities of the external field. I argue that the conclusion drawn from this approach is not valid for explaining jerks as caused by external events and not valid to describe the global secular variation. In the second part a time--dependent model of the secular variation between 1980 and 2000 is developed. The endpoints of the time interval were chosen, because of the availability of high quality field models from satellite data for these epochs. The Gauss coefficients are expanded in time as function of cubic B--splines. This model is forced to fit field models from high quality vector measurements from MAGSAT in 1980 and OERSTED in 2000. The methodology is new. The model is a valuable extension of the hitherto existing time--dependent description of the secular variation, the GUFM which was valid until 1990. Unlike GUFM the model is based on observatory monthly means, and the knot spacing of the cubic B--Splines tighter than GUFM. Therefore it reveals a short term secular variation on subdecadal time scale, which was not as yet resolved. The model is also valuable to test the frozen flux hypothesis and to link some of the morphology of the radial field at the core--mantle boundary to the geodynamo. The third part of this thesis deals with the inversion of the time--dependent field and secular variation model for different kinds of core surface flow. These flows allow prediction of the decadal change of the length of the day, an observable which is independent to geomagnetic data. The prediction of some of the flows have the right tendency, but differ in slope from the observed change of the length of the day.

Description: The Central European Basin System is one of the basins where the sedimentary cover is strongly affected by salt tectonics. The most significant stage of salt movement occurred during the Triassic. The largest Triassic subsidence occurred in the different sub-basins surrounding the Ringkoebing-Fyn High such as the Horn Graben, the Danish Basin and the Glueckstadt Graben. Furthermore, the thickest Triassic succession is observed in the Glueckstadt Graben where it reaches more than 9000 m. In the present study, the structure and the Permian to recent evolution of the Glueckstadt Graben are investigated by use of borehole data, seismic lines and 3D structural modelling. The evaluation of the diverse deformation patterns of the sedimentary cover and their relations to salt structures show that the strongest salt movements occurred at the beginning of the Keuper when the Gluckstadt Graben was affected by extension. The onlap patterns of the Jurassic sediments onto the top of the Keuper succession indicate essential changes of the sedimentation style during the Jurassic. Thick Jurassic sediments are only observed around salt structures and are thinning away from salt walls or salt stocks. The Upper Cretaceous strata have an approximately constant thickness and the parallel reflections patterns indicate a quiet tectonic setting with very minor salt movements in the Late Cretaceous. Renewed salt flow during the Paleogene-Neogene caused rapid subsidence along the marginal parts of the Central Triassic Graben in the Westholstein, the Eastholstein and the Hamburger troughs. The thick Paleogene-Neogene strata within the marginal troughs may also be related to a regional component of tectonic subsidence in the area, contemporary with rapid subsidence in the North Sea. The 3D modelling approach has been used to determine salt distribution at certain paleo-levels in response to unloading due to sequential removing of the stratigraphic layers. The modelling approach was also aimed to reconstruct the original Permian salt distribution immediately after deposition. The initial salt thickness varies from 1300 m at the flanks of the basin up to 3000 m within the central part and demonstrates a clear NNE-SSW trend of the basin. The regional trend of the restored salt distribution points to a westward continuation of the Permian salt basin. The formation of the deep Central Triassic Graben and the subsequent Jurassic- Cenozoic marginal troughs was strongly controlled by the development of salt structures through time. It is shown that the depocentre of sedimentation was moving away from the central part of the of the original Graben structure towards its margins. The evaluation of the available data and results of the 3D reverse modelling demonstrate that a greater amount of subsidence occurred close to the active salt structures, and may have resulted in gradual depletion of Permian salt. Thus, this study indicates that the source of such long-term subsidence is derived from gradual depletion of the Permian salt, which started within the axial part of the basin and moved towards the basin flanks with time. In this sense, the Glueckstadt Graben was formed at least partially as a “basin-scale rim syncline” during post-Permian times. Therefore, the results show that salt withdrawal may have played an important role during the Meso-Cenozoic evolution and that the effects of salt-driven subsidence during the Meso-Cenozoic can be considered the main reason for the formation of the deep Central Triassic Graben and the subsequent Jurassic-Cenozoic marginal troughs.

Description: Das zentraleuropäische Beckensystem ist eines der Becken, in denen die Sedimentdecken stark durch Salztektonik beeinflusst sind. Die stärksten salztektonischen Aktivitäten traten während der Trias auf. Die größte triassische Subsidenz erfolgte in den verschiedenen Unterbecken rund um das Ringköbing-Fünen Hoch (Horn Graben, Dänisches Becken, Glückstadt Graben). Die mächtigste triassische Abfolge wurde im Glückstadtgraben beobachtet, wo sie mehr als 9000 m Mächtigkeit erreicht. In der vorliegenden Studie wurden die Struktur sowie die Entwicklung des Glückstadt Grabens vom Perm bis heute mit Hilfe von Bohrdaten, seismischen Linien und 3D-Strukturmodellierung untersucht. Die Auswertung der verschiedenen Deformationsmuster der Sedimentdecke und ihr Bezug zu Salzstrukturen zeigen, dass die stärksten Salzbewegungen am Beginn des Keupers, während einer Dehnung des Glückstadt Graben auftraten. Die jurassischen Sedimente zeigen dann eine grundlegende Änderungen der Sedimentationsart während des Jura an. Mächtige jurassische Sedimente treten nur rund um Salzstrukturen auf und dünnen mit zunehmender Entfernung von Salzmauern oder Salzstöcken aus. Die Oberkreideschichten haben eine annähernd konstante Mächtigkeit, und die parallelen Reflektionsmuster weisen auf eine ruhige tektonische Subsidenz mit geringen Salzbewegungen in der Oberkreide hin. Erneute Salzbewegungen während des Paläogens-Neogens verursachten schnelle Subsidenz entlang der Randbereiche des zentraltriassischen Grabens, den Westholstein, Ostholstein und Hamburger Trögen. Die mächtigen paläogen-neogenen Schichten innerhalb der Randtröge sind eventuell auch mit einer regionalen Komponente tektonischer Subsidenz verbunden, zeitgleich mit schneller Subsidenz in der Nordsee. Der 3D- Modellierungsansatz wurde genutzt, um die Salzverteilung für verschiedenen Paläolevels als Reaktion auf Entlastung durch sequentielles Entfernen der stratigraphischen Schichten zu bestimmen. Mit dem Modellierungsansatz wurde auch versucht, die ursprüngliche permische Salzverteilung unmittelbar nach der Ablagerung zu rekonstruieren. Die ursprüngliche Salzmächtigkeit variiert zwischen 1300 m an den Beckenflanken und bis zu 3000 m innerhalb des zentralen Teils und zeigt einen klaren NNO-SSW-Trend innerhalb des Beckens. Die Bildung des tiefen zentraltriassischen Grabens und der nachfolgenden jurassisch- känozoischen Randtröge wurde stark durch die langandauernde Entwicklung von Salzstrukturen kontrolliert. Es wird gezeigt, dass das Sedimentationszentrum sich vom Zentralteil der ursprünglichen Grabenstruktur in Richtung ihrer Ränder verlagerte. Die Auswertung der verfügbaren Daten und die Ergebnisse der 3D-Rückwärtsmodellierung zeigen, dass der größte Teil der Subsidenz nahe aktiver Salzstrukturen auftrat, und eventuell zu einer graduellen Abwanderung permischer Salze führte. Daher zeigt die Studie, dass die Ursache der langzeitigen Subsidenz die graduelle Abwanderung permischen Salzes ist, welche im axialen Teil des Beckens begann und sich im Laufe der Zeit in Richtung der Beckenflanken bewegte. In diesem Sinne wurde der Glückstadtgraben zumindest teilweise in nachpermischer Zeit als basin-scale rim syncline geformt. Daher zeigen die Ergebnisse, dass dieser Salzrückzug während der meso-känozoischen Evolution eine bedeutende Rolle gespielt haben dürfte, und dass die Effekte salzgesteuerter Subsidenz während des Meso-Känozoikums als Hauptursache der Bildung des tiefen zentraltriassischen Grabens und die nachfolgenden jurasso- känozoischen Tröge angesehen werden kann.

Description: Mit der vorliegenden Arbeit werden voneinander unabhängige Experimente zur Untersuchung der elektrischen Leitfähigkeit im Untergrund miteinander verknüpft, mit dem Ziel, das Potenzial der Methode Magnetotellurik für das Abbilden aktiver und fossiler tektonischer Systeme aufzuzeigen. Die Magnetotellurik hat sich in den letzten zehn bis fünfzehn Jahren zunehmend zu einem zuverlässigen und aussagekräftigen Tiefensondierungsverfahren entwickelt. Dieser positive Entwicklungsprozess wird auch durch meine Forschungsergebnisse dokumentiert, die in verschiedenen Projekten während meiner Zeit am GeoForschungsZentrum entstanden sind. Eine Übersicht über die verwendeten Arbeiten befindet sich in Tabelle 1.1. Große geophysikalische Feldexperimente, wie die hier beschriebenen Magnetotellurikprojekte, lassen sich nur im Team durchführen. Im akademischen Bereich bedeutet dies die Integration von Studenten und Doktoranden bei den Feldmessungen und der anschließenden Bearbeitung der Daten. Entsprechend gehen einige der in Tabelle 1.1 aufgeführten Arbeiten auf Diplomarbeiten oder Promotionsschriften zurück, die von mir mitbetreut wurden. Bei anschließender Veröffentlichung der Arbeiten habe ich als Co-Autor mitgewirkt. Die beiliegenden Veröffentlichungen enthalten eine Einführung in die Methode der Magnetotellurik und gegebenenfalls die Beschreibung neu entwickelter Methoden. Eine allgemeine Darstellung der theoretischen Grundlagen der Magnetotellurik findet man z.B. in (Kaufman & Keller, 1981; Nabighian, 1987; Weaver, 1994). Am Ende der Arbeit befindet sich ein Glossar, in dem einige Begriffe und Abkürzungen erklärt werden.