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  • English  (4,307)
  • German  (1)
  • 2010-2014  (4,308)
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Year
  • 1
    Monograph available for loan
    Monograph available for loan
    Stuttgart : Schweizerbart Science Publishers ; Volume 1, number 1 (1978)-
    Call number: M 18.91571
    Type of Medium: Monograph available for loan
    Pages: 134 Seiten
    ISSN: 2363-7196
    Series Statement: Global tectonics and metallogeny : special issue Vol. 10/2-4
    Classification:
    Tectonics
    Parallel Title: Erscheint auch als Global tectonics and metallogeny
    Language: English
    Location: Upper compact magazine
    Branch Library: GFZ Library
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  • 2
    Call number: 3/S 07.0034(2016)
    In: Annual report
    Type of Medium: Monograph available for loan
    Pages: 51 Seiten
    ISSN: 1865-6439 , 1865-6447
    Parallel Title: Erscheint auch als Annual report ... / Helmholtz Association of German Research Centres
    Language: English
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  • 3
    Monograph available for loan
    Monograph available for loan
    [Edgecumbe, N.Z.] : A. Muller
    Call number: M 15.89146
    Description / Table of Contents: An account of the results of the 2 March 1987 earthquake in the eastern Bay of Plenty and the aftermath's effects on the people and places on the Rangitaiki Plains
    Type of Medium: Monograph available for loan
    Pages: 223 S., , Ill.
    Language: English
    Branch Library: GFZ Library
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  • 4
    Call number: Z 06.0500
    Type of Medium: Journal available for loan
    Pages: 30 cm
    ISSN: 1824-7741
    Former Title: Vorgänger Geologisch-paläontologische Mitteilungen, Innsbruck
    Language: German , English
    Note: Ersch. unregelmäßig , Beiträge teilweise in Englisch
    Branch Library: GFZ Library
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  • 5
    Monograph available for loan
    Monograph available for loan
    Garmisch-Partenkirchen : Institut für atmosphärische Umweltforschung der Fraunhofer- Gesellschaft
    Call number: MOP 44829 / Mitte
    Type of Medium: Monograph available for loan
    Pages: 25 S. , graph. Darst.
    Language: English
    Location: MOP - must be ordered
    Branch Library: GFZ Library
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  • 6
    Monograph available for loan
    Monograph available for loan
    London : Penguin Books
    Type of Medium: Monograph available for loan
    ISBN: 9780141985206
    Language: English
    Branch Library: RIFS Library
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  • 7
    Journal available for loan
    Journal available for loan
    Tübingen : Mohr Siebeck ; 1.1884 - 48.1931; N.F. 1.1932/33 - 10.1943/44(1945),3; 11.1948/49(1949) -
    Call number: ZS 22.95039
    Type of Medium: Journal available for loan
    Pages: Online-Ressource
    ISSN: 1614-0974 , 0015-2218 , 0015-2218
    Language: German , English
    Note: N.F. entfällt ab 57.2000. - Volltext auch als Teil einer Datenbank verfügbar , Ersch. ab 2000 in engl. Sprache mit dt. Hauptsacht.
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  • 8
    Monograph non-lending collection
    Monograph non-lending collection
    Leiden : Nijhoff ; 1.2009 -
    Call number: IASS 17.92082
    Type of Medium: Monograph non-lending collection
    ISSN: 1876-8814
    Language: English
    Branch Library: RIFS Library
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  • 9
  • 10
    Publication Date: 2020-02-12
    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.
    Language: English
    Type: info:eu-repo/semantics/report
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  • 11
    Publication Date: 2020-02-12
    Language: English
    Type: info:eu-repo/semantics/doctoralThesis
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  • 12
    Publication Date: 2020-02-12
    Language: English
    Type: info:eu-repo/semantics/article
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  • 13
    Publication Date: 2020-02-12
    Language: English
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  • 14
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    International Association of Geodesy (IAG)
    In:  IAG Annual Report
    Publication Date: 2020-02-12
    Language: English
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  • 15
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    Deutsches GeoForschungsZentrum GFZ
    In:  Scientific Technical Report STR - Data
    Publication Date: 2020-02-12
    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.
    Language: English
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  • 16
    Publication Date: 2020-02-12
    Language: English
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  • 17
    Publication Date: 2020-02-12
    Language: English
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  • 18
    Publication Date: 2020-04-20
    Description: This paper presents the first published 3D geomechanical modelling study of the CO2CRC Otway Project, located in the state of Victoria, Australia. The results of this work contribute to one of the main objectives of the CO2CRC, which is to demonstrate the feasibility of CO2 storage in a depleted gas reservoir. With this aim in mind, a one-way coupled flow and geomechanics model is presented, with the capability of predicting changes to the in situ stress field caused by changes in reservoir pressure owing to CO2 production and injection. A parametric study investigating the pore pressures required to reactivate key, reservoir-bounding faults has been conducted, and the results from the numerical simulation and analytical analysis are compared. The numerical simulation indicates that the critical pore fluid pressure to cause fault reactivation is 1.15 times the original pressure as opposed to 1.5 times for the comparable analytical model. Possible reasons for the differences between the numerical and analytical models can be ascribed to the higher degree of complexity incorporated in the numerical model. Heterogeneity in terms of lateral variations of hydrological and mechanical parameters, effect of topography, presence of faults and interaction between cells are considered to be the main sources for the different estimation of critical pore pressure. The numerical model, which incorporates this greater complexity, is able then to better describe the state of stress that acts in the subsurface compared with a simple 1D analytical model. Moreover, the reactivation pressures depend mainly on the state of stress described; therefore we suggest that numerical models be performed when possible.
    Language: English
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  • 19
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    In:  Geophysical Research Letters
    Publication Date: 2021-03-16
    Description: We investigate the feedbacks between surface processes and tectonics in an extensional setting by coupling a 2‐D geodynamical model with a landscape evolution law. Focusing on the evolution of a single normal fault, we show that surface processes significantly enhance the amount of horizontal extension a fault can accommodate before being abandoned in favor of a new fault. In simulations with very slow erosion rates, a 15 km thick brittle layer extends via a succession of crosscutting short‐lived faults (heave 〈 5 km). By contrast, when erosion rates are comparable to the regional extension velocity, deformation is accommodated on long‐lived faults (heave 〉10 km). Using simple scaling arguments, we quantify the effect of surface mass removal on the force balance acting on a growing normal fault. This leads us to propose that the major range‐bounding normal faults observed in many continental rifts owe their large offsets to erosional and depositional processes.
    Language: English
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  • 20
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    In:  Geophysical Research AbstractsVol. 16, EGU2014-6725-1, 2014
    Publication Date: 2021-02-26
    Description: With the upcoming launch of the next generation of hyperspectral satellites that will routinely deliver high spectral resolution images for the entire globe (e.g. EnMAP, HISUI, HyspIRI, HypXIM, PRISMA), an increasing demand for the availability/accessibility of hyperspectral soil products is coming from the geoscience community. Indeed, many robust methods for the prediction of soil properties based on imaging spectroscopy already exist and have been successfully used for a wide range of soil mapping airborne applications. Nevertheless, these methods require expert know-how and fine-tuning, which makes them used sparingly. More developments are needed toward easy-to-access soil toolboxes as a major step toward the operational use of hyperspectral soil products for Earth's surface processes monitoring and modelling, to allow non-experienced users to obtain new information based on non-expensive software packages where repeatability of the results is an important prerequisite. In this frame, based on the EU-FP7 EUFAR (European Facility for Airborne Research) project and EnMAP satellite science program, higher performing soil algorithms were developed at the GFZ German Research Center for Geosciences as demonstrators for end-to-end processing chains with harmonized quality measures. The algorithms were built-in into the HYSOMA (Hyperspectral SOil MApper) software interface, providing an experimental platform for soil mapping applications of hyperspectral imagery that gives the choice of multiple algorithms for each soil parameter. The software interface focuses on fully automatic generation of semi-quantitative soil maps such as soil moisture, soil organic matter, iron oxide, clay content, and carbonate content. Additionally, a field calibration option calculates fully quantitative soil maps provided ground truth soil data are available. Implemented soil algorithms have been tested and validated using extensive in-situ ground truth data sets. The source of the HYSOMA code was developed as standalone IDL software to allow easy implementation in the hyperspectral and non-hyperspectral communities. Indeed, within the hyperspectral community, IDL language is very widely used, and for non-expert users that do not have an ENVI license, such software can be executed as a binary version using the free IDL virtual machine under various operating systems. Based on the growing interest of users in the software interface, the experimental software was adapted for public release version in 2012, and since then ~80 users of hyperspectral soil products downloaded the soil algorithms at www.gfz-potsdam.de/hysoma. The software interface was distributed for free as IDL plug-ins under the IDL-virtual machine. Up-to-now distribution of HYSOMA was based on a close source license model, for non-commercial and educational purposes. Currently, the HYSOMA is being under further development in the context of the EnMAP satellite mission, for extension and implementation in the EnMAP Box as EnSoMAP (EnMAP SOil MAPper). The EnMAP Box is a freely available, platform-independent software distributed under an open source license. In the presentation we will focus on an update of the HYSOMA software interface status and upcoming implementation in the EnMAP Box. Scientific software validation, associated publication record and users responses as well as software management and transition to open source will be discussed.
    Language: English
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  • 21
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    In:  New Manual of Seismological Observatory Practice 2 (NMSOP-2)
    Publication Date: 2020-02-12
    Language: English
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  • 22
    Publication Date: 2020-02-12
    Description: Splay faults, large thrust faults emerging from the plate boundary to the seafloor in subduction zones, are considered to enhance tsunami generation by transferring slip from the very shallow dip of the megathrust onto steeper faults, thus increasing vertical displacement of the seafloor. These structures are predominantly found offshore, and are therefore difficult to detect in seismicity studies, as most seismometer stations are located onshore. The Mw (moment magnitude) 8.8 Maule earthquake on 27 February 2010 affected ~500 km of the central Chilean margin. In response to this event, a network of 30 ocean-bottom seismometers was deployed for a 3 month period north of the main shock where the highest coseismic slip rates were detected, and combined with land station data providing onshore as well as offshore coverage of the northern part of the rupture area. The aftershock seismicity in the northern part of the survey area reveals, for the first time, a well-resolved seismically active splay fault in the submarine forearc. Application of critical taper theory analysis suggests that in the northernmost part of the rupture zone, coseismic slip likely propagated along the splay fault and not the subduction thrust fault, while in the southern part it propagated along the subduction thrust fault and not the splay fault. The possibility of splay faults being activated in some segments of the rupture zone but not others should be considered when modeling slip distributions.
    Language: English
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  • 23
    Publication Date: 2020-02-12
    Description: Generating data catalogue pages from ISO19139, GMCD-DIF and Datacite metadata
    Language: English
    Type: info:eu-repo/semantics/other
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  • 24
    Publication Date: 2020-02-12
    Description: Due to its remoteness, the CO2 Lab close to the town of Longyearbyen on Svalbard presents a unique opportunity to demonstrate the entire CO2 value chain based on its closed energy system. The formation considered as potential CO2 storage unit consists of mixed sandstone and shale beds, presenting itself as a fractured, low-permeability reservoir. A geophone network surrounding the injection well has been installed to locate microseismic events during injection tests and to estimate background seismicity. During the first water injection in 2010, a microseismic event (M ∼ 1) was recorded and located close to the injection well, followed by a series of aftershocks. Later injection tests did not generate any detectable microseismic events; nevertheless, pressure and flow rate showed a pattern characteristic for fracture opening potentially indicating “aseismic” fracture propagation. Records of ambient seismic noise are analysed by a cross-correlation method in order to reconstruct the impulse functions between sensors. The daily cross-correlations are dominated by tube wave signals originating from the bottom of the well showing a sudden increase of activity. We also demonstrate a noise cancellation method exhibiting great potential towards cancellation of electromagnetic and cultural noise. Albeit several difficulties that were approached at the CO2 Lab, new knowledge and guidelines for best practice containment monitoring using seismic methods in the Arctic could be developed.
    Language: English
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  • 25
    Publication Date: 2020-02-12
    Language: English
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  • 26
    Publication Date: 2020-02-12
    Language: English
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  • 27
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    IUGG Secretariat, GFZ German Research Centre for Geosciences
    In:  IUGG Publications
    Publication Date: 2021-04-23
    Language: French , English
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  • 28
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    In:  New Manual of Seismological Observatory Practice 2 (NMSOP 2)
    Publication Date: 2020-02-12
    Language: English
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  • 29
    Publication Date: 2020-02-12
    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.
    Language: English
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  • 30
    Publication Date: 2020-02-12
    Description: A joint earthquake source inversion technique is presented that uses InSAR and long-period teleseismic data, and, for the first time, takes 3-D Earth structure into account when modelling seismic surface and body waves. Ten average source parameters (Moment, latitude, longitude, depth, strike, dip, rake, length, width and slip) are estimated; hence, the technique is potentially useful for rapid source inversions of moderate magnitude earthquakes using multiple data sets. Unwrapped interferograms and long-period seismic data are jointly inverted for the location, fault geometry and seismic moment, using a hybrid downhill Powell–Monte Carlo algorithm. While the InSAR data are modelled assuming a rectangular dislocation in a homogeneous half-space, seismic data are modelled using the spectral element method for a 3-D earth model. The effect of noise and lateral heterogeneity on the inversions is investigated by carrying out realistic synthetic tests for various earthquakes with different faulting mechanisms and magnitude (Mw 6.0–6.6). Synthetic tests highlight the improvement in the constraint of fault geometry (strike, dip and rake) and moment when InSAR and seismic data are combined. Tests comparing the effect of using a 1-D or 3-D earth model show that long-period surface waves are more sensitive than long-period body waves to the change in earth model. Incorrect source parameters, particularly incorrect fault dip angles, can compensate for systematic errors in the assumed Earth structure, leading to an acceptable data fit despite large discrepancies in source parameters. Three real earthquakes are also investigated: Eureka Valley, California (1993 May 17, Mw 6.0), Aiquile, Bolivia (1998 February 22, Mw 6.6) and Zarand, Iran (2005 May 22, Mw 6.5). These events are located in different tectonic environments and show large discrepancies between InSAR and seismically determined source models. Despite the 40–50 km discrepancies in location between previous geodetic and seismic estimates for the Eureka Valley and Aiquile earthquakes, the seismic data are found to be compatible with the InSAR location. A 30° difference in strike between InSAR and seismic-derived source models is also resolved when taking 3-D Earth structure into account in the analysis of the Eureka Valley earthquake. The combination of both InSAR and seismic data further constrains the dip for the Zarand earthquake, and in all cases the seismic moment is more robustly constrained in the joint inversions than in the individual data set inversions. Unmodelled lateral heterogeneities in Earth and the models could partly explain some of the observed source parameter discrepancies related to the seismic data.
    Language: English
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  • 31
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    Deutsches GeoForschungsZentrum GFZ
    In:  Scientific Technical Report
    Publication Date: 2020-02-12
    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.
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  • 32
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    IUGG Secretariat, GFZ German Research Centre for Geosciences
    Publication Date: 2020-02-12
    Language: English
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  • 33
    Publication Date: 2020-02-12
    Language: English
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  • 34
    Publication Date: 2020-02-12
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  • 35
    Publication Date: 2020-02-12
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  • 36
    Publication Date: 2020-02-12
    Description: Cross-correlation of continuous broadband records allows the retrieval of body waves at teleseismic distances. These continuous records mainly contain low-amplitude background noise that comes from ocean–crust interactions, although there are also many transient events of different magnitudes and their coda associated with reverberation and/or scattering. We present an analysis at the global scale of these different contributions in the context of body-wave retrieval using the cross-correlation technique. Specifically, we compare the correlation of long codas after strong earthquakes with those of the quietest days. In the long period range (25–100 s), several phases that propagate in the deep Earth are observed in the correlations of the signals recorded after earthquakes, with some of these phases showing non-physical polarization. At the same time, the global section of correlations shows a series of spurious branches. These features are reproduced with synthetic correlations. A stack of the quietest days of the year shows that body waves are still present, with relative amplitudes that are closer to those expected for the actual Earth response. When considering shorter periods (5–10 s), the reconstruction of the deep phases is not affected by the earthquake coda, due to the dominance of scattering over reverberation.
    Language: English
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  • 37
    Publication Date: 2020-02-12
    Description: Reassessment of travel time data from an exceptionally dense, amphibious, temporary seismic network on- and offshore Central and Eastern Java (MERAMEX) confirms the accretionary nature of the crust in this segment of the Sunda subduction zone (109.5–111.5E). Traveltime data of P- and S-waves of 244 local earthquakes were tomographically inverted, following a staggered inversion approach. The resolution of the inversion was inspected by utilizing synthetic recovery tests and analyzing the model resolution matrix. The resulting images show a highly asymmetrical crustal structure. The images can be interpreted to show a continental fragment of presumably Gondwana origin in the coastal area (east of 110E), which has been accreted to the Sundaland margin. An interlaced anomaly of high seismic velocities indicating mafic material can be interpreted to be the mantle part of the continental fragment, or part of obducted oceanic lithosphere. Lower than average crustal velocities of the Java crust are likely to reflect ophiolitic and metamorphic rocks of a subduction melange.
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  • 38
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    Deutsches GeoForschungsZentrum GFZ
    In:  Scientific Technical Report
    Publication Date: 2020-02-12
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  • 39
    Publication Date: 2020-02-12
    Description: The Lorca 2011 seismic series was recorded by an unprecedented set of high quality on scale broadband seismograms and strong motion accelerograms. The waveforms from permanent and temporary broadband seismic networks deployed in the region by different institutions allowed to invert regional moment tensor for the fore, main and largest aftershock of the complete seismic sequence. Using double-difference algorithm we have performed a precise relocation of the seismic series, where body wave travel times from strong ground motion accelerograms were included in the data set. Regional moment tensor inversion for the three main events show similar oblique-reverse faulting regime with a northeast-southwest fault orientation. The scalar seismic moment, moment magnitude and focal depth retrieved from the inversion yield the following values for each event: Mo=6.5×1016 Nm (Mw = 5.2) for the mainshock, Mo=9.6×1015 Nm (Mw = 4.6) for the foreshock and Mo=7.3×1014 Nm (Mw = 3.9) for the large aftershock. The centroid depths range between 4 and 6 km. The double-difference relocation of the seismic series shows significant epicentral differences with the preliminary routine location. The epicentral solutions given by this relocation show a seismic sequence distributed following a NE–SW strike, subparallel to the Alhama de Murcia fault and compatible with the faulting parameters inverted from the moment tensor analysis. The hypocenters of the series generate a subvertical trend in depth distribution, being concentrated between 2 and 6 km. The depth distribution of the main events, which range from 4.6 to 5.5 km, is in good relationship with the faulting and depth parameters deduced from the moment tensor inversion technique. The regional moment tensor solutions for the three largest earthquakes, the epicentral distribution and the focal depths show good relationship with the surface geometry and tectonic regime of the Alhama de Murcia fault. The stress drop deduced for the mainshock gives a value ranging between 58 and 85 bars, which does not support the idea of a high stress drop release as a main factor contributing to the high ground acceleration recorded at Lorca. The PGA values observed at Lorca, which contributed to the high damage independently of structural deficiencies, could be generated mainly by shallowness and proximity to the seismic source together with a directivity effect in the seismic radiation.
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  • 40
    Publication Date: 2020-02-12
    Language: German , English
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  • 41
    Publication Date: 2020-02-12
    Language: English
    Type: info:eu-repo/semantics/lecture
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  • 42
    Publication Date: 2020-02-12
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  • 43
    Publication Date: 2020-02-12
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  • 44
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    In:  Proceedings of the Royal Society B : Biological Sciences
    Publication Date: 2020-02-12
    Description: Retreating ice fronts (as a result of a warming climate) expose large expanses of deglaciated forefield, which become colonized by microbes and plants. There has been increasing interest in characterizing the biogeochemical development of these ecosystems using a chronosequence approach. Prior to the establishment of plants, microbes use autochthonously produced and allochthonously delivered nutrients for growth. The microbial community composition is largely made up of heterotrophic microbes (both bacteria and fungi), autotrophic microbes and nitrogen-fixing diazotrophs. Microbial activity is thought to be responsible for the initial build-up of labile nutrient pools, facilitating the growth of higher order plant life in developed soils. However, it is unclear to what extent these ecosystems rely on external sources of nutrients such as ancient carbon pools and periodic nitrogen deposition. Furthermore, the seasonal variation of chronosequence dynamics and the effect of winter are largely unexplored. Modelling this ecosystem will provide a quantitative evaluation of the key processes and could guide the focus of future research. Year-round datasets combined with novel metagenomic techniques will help answer some of the pressing questions in this relatively new but rapidly expanding field, which is of growing interest in the context of future large-scale ice retreat.
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  • 45
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    Publication Date: 2020-02-12
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  • 46
    Publication Date: 2020-02-12
    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.
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  • 47
    Publication Date: 2020-02-12
    Language: English
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  • 48
    Publication Date: 2020-02-12
    Description: The ratio of seismic P- to S-wave velocities (the Vp/Vs ratio) of a given rock volume is a sensitive proxy for the detection of fluids and melts. In subduction regimes it has often been inferred from seismic tomography and been used, e.g., to detect pathways of ascending melt above the seismogenic zone, where tomographic methods have their highest resolution. We present Vp/Vs ratios that were computed using only seismic arrival time observations following the approach of Lin and Shearer (2007). This approach has its highest sensitivity in the source volume of a set of nearby seismic events and is hence particularly well suited to directly probe the plate interface. We present data from a temporary local network of short period seismometers that was in operation in the forearc of the Central Andean subduction zone at 21 ◦ S between 2005 and 2012. From this database we were able to localize 3253 seismic events (Ml ∼ 0.5–4) with high precision, yielding a detailed image of the seismicity distribution in this region. Seismicity is pervasive within the entire crust of the South American continental plate and exhibits three distinct bands in the subducting slab, the lowermost one being located in the lithospheric mantle of the subducting plate. The highest concentration of seismic events is found in the contact zone between the continental and the oceanic lithosphere at depths between 30 and 50 km. We group seismic events into approximately 100 subsets of nearby events that origin from the same geo- logical structure. For about half of these subsets we are able to extract a reliable local Vp/Vs ratio. In the middle continental crust, Vp/Vs ratios show slightly enhanced values ( ∼ 1.75). In the lower continental crust towards the plate interface they tend to increase from this value updip and decrease downdip. At the plate interface itself, we observe higher Vp/Vs ratios (〉1.8) at shallower depths (between 20 and 40 km). Downdip (40–60 km depth) Vp/Vs ratios decrease to rather typical values ( ∼ 1.75). The same trend is observed in the lowermost band of mantle seismicity in the subducting slab. Below 80 km depth, where mineral transitions toward the eclogite facies are expected to occur, Vp/Vs ratios tend to be low (〈1.75). The consistently high Vp/Vs ratios in the shallow part of the subducting slab hint at the presence of fluids in the porespace of the subducting lithosphere there. In the deeper part, downdip variations of Vp/Vs may be attributed to mineral phase transitions due to the changing P-T-conditions along the subduction pathway.
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  • 49
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    DCE – Danish Centre for Environment and Energy, Aarhus Univ.
    Publication Date: 2020-02-12
    Description: This book is about management of arctic and northern alpine research stations. It has been produced by a group of station managers participating in the EU 7th Framework Programme Infrastructure project called INTERACT. With this book we want to share the knowledge and experiences we have gained from managing very different research stations in very different environmental and climatic settings. The target audience for the book is mainly managers of research stations in arctic and alpine areas, but we hope that it will also be useful for others involved in science coordination and logistics, e.g. research institutions, chief scientists and expedition planners. The book has been produced mainly based on input from practising station managers being part of ‘INTERACT Station Managers’ Forum (SMF), a forum established to provide a platform for exchange of information between station managers and other participants within INTERACT, and to collect and disseminate knowledge embedded within the network. The scope of this book is to identify and describe best practices and key considerations of relevance to station management under arctic and alpine conditions. As research stations operate under very different legal regimes, financial conditions, environmental and climatic conditions, as well as remoteness, it is not possible to identify specific best practices that fit all stations. Instead, we have described key issues that should be considered and addressed by station management, and supplemented this with examples of good practices from stations operating under different conditions (e.g. different climate, remoteness or size).
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  • 50
    Publication Date: 2020-02-12
    Description: Based on a 2 year seismic record from a local network, we characterize the deformation of the seismogenic crust of the Pamir in the northwestern part of the India‐Asia collision zone. We located more than 6000 upper crustal earthquakes in a regional 3‐D velocity model. For 132 of these events, we determined source mechanisms, mostly through full waveform moment tensor inversion of locally and regionally recorded seismograms. We also produced a new and comprehensive neotectonic map of the Pamir, which we relate to the seismic deformation. Along Pamir's northern margin, where GPS measurements show significant shortening, we find thrust and dextral strike‐slip faulting along west to northwest trending planes, indicating slip partitioning between northward thrusting and westward extrusion. An active, north‐northeast trending, sinistral transtensional fault system dissects the Pamir's interior, connecting the lakes Karakul and Sarez, and extends by distributed faulting into the Hindu Kush of Afghanistan. East of this lineament, the Pamir moves northward en bloc, showing little seismicity and internal deformation. The western Pamir exhibits a higher amount of seismic deformation; sinistral strike‐slip faulting on northeast trending or conjugate planes and normal faulting indicate east‐west extension and north‐south shortening. We explain this deformation pattern by the gravitational collapse of the western Pamir Plateau margin and the lateral extrusion of Pamir rocks into the Tajik‐Afghan depression, where it causes thin‐skinned shortening of basin sediments above an evaporitic décollement. Superposition of Pamir's bulk northward movement and collapse and westward extrusion of its western flank causes the gradual change of surface velocity orientations from north‐northwest to due west observed by GPS geodesy. The distributed shear deformation of the western Pamir and the activation of the Sarez‐Karakul fault system may ultimately be caused by the northeastward propagation of India's western transform margin into Asia, thereby linking deformation in the Pamir all the way to the Chaman fault in the south in Afghanistan.
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  • 51
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    Deutsches GeoForschungsZentrum GFZ
    In:  Scientific Technical Report
    Publication Date: 2020-02-12
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  • 52
    Publication Date: 2020-02-12
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  • 53
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    GFZ Data Services
    Publication Date: 2020-02-12
    Description: Dataset
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  • 54
    Publication Date: 2020-02-12
    Description: To obtain a precise record of the foreshock sequence before the 2014 Iquique, Chile Mw 8.1 earthquake, we applied a matched filter technique to continuous seismograms recorded near the source region. We newly detected about 10 times the number of seismic events listed in the routinely constructed earthquake catalog and identified multiple sequences of earthquake migrations at speeds of 2–10 km/d, both along strike and downdip on the fault plane, updip of the main shock area. In addition, we found out repeating earthquakes from the newly detected events, likely indicating aseismic slip along the plate boundary fault during the foreshock sequence. These observations suggest the occurrence of multiple slow-slip events updip of the main shock area. The final slow-slip event migrated toward the main shock nucleation point. We interpret that several parts of the plate boundary fault perhaps experienced slow slip, causing stress loading on the prospective largest slip patch of the main shock rupture.
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  • 55
    Publication Date: 2020-02-12
    Description: Two devastating earthquakes with moment magnitudes of 7.2 and 5.6 occurred on October 23, 2011 (Van-Erciş earthquake) and November 9, 2011 (Van-Edremit earthquake), respectively, in the Van Province of the eastern Turkey. The Van-Erciş and Van-Edremit earthquakes caused 604 and 38 fatalities, respectively, and heavy damage to buildings and other structures, particularly in Erciş town and Van City. In this study, characteristics of both main shocks and their geotechnical aspects, such as local site conditions, liquefaction phenomena and associated ground deformations and slope failures are evaluated. The failures of slopes and embankments and rock falls and ground liquefaction may also be indications of diluted ground deformation caused by the earthquake fault. It seems that a wedge-like body bounded by two fault planes was uplifted. As a result of this movement, the northern shoreline of Van Lake uplifted. The November 9, 2011 Van-Edremit earthquake was triggered due to the variation of crustal stresses induced by the October 23, 2011 earthquake. The effects of local site conditions have contributed to the damage of some parts of Erciş city and its vicinity; however, the ground liquefaction was not observed in the city as anticipated. With a magnitude of 5.6, the Van-Edremit earthquake is probably the smallest magnitude earthquake to cause liquefaction in Turkey so far.
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  • 56
    Publication Date: 2020-02-12
    Description: Paleozoic siliciclastic rocks from the Schwarzburg area of the German Saxo-Thuringian Zone encompass a 250 Ma peri-Gondwanan sedimentary record from the Cadomian to the Variscan orogenies. The sediments were deposited in environments that changed through time from terrestrial to shallow marine, deep marine, and eventually with the onset of the Variscan orogeny back to shallow marine and terrestrial again. Even for rocks of only minor major-element variability, the isotopic compositions of Li and B may encompass a range of more than 20 δ-units, depending on the weathering history of their source, the environment of deposition (terrestrial, lacustrine, marine), and post-depositional alteration. In particular, the relative contributions of structure-bound and exchangeable Li and B has a major effect on the isotopic composition of the bulk sample and may result in a decoupling of the Li and B isotopic compositions in sedimentary rocks. The Li isotopic composition shows little variation, except for deeply weathered Permian shales that were deposited in a terrestrial environment (slightly lower δ7Li values) and deeply weathered early Ordovician deposits that have been redeposited in a marine environment and have very high δ7Li values due to high contributions of exchangeable Li. The B isotopic composition shows for early Paleozoic sedimentary rocks a systematic increase in δ11B from − 24.0‰ to − 4.2‰ that in part reflects the change from terrestrial to open marine deposition and in part is due to mineralogical variation. The δ11B values of post-Hirnantian (late Ordovician) sedimentary rocks range from − 15‰ to − 5.2‰. There is no significant effect of the sediment source or protolith nature on the Li isotopic composition of the siliciclastic sedimentary rocks. Instead, major variations in the Li and B isotopic composition are controlled by depositional environment (terrestrial vs. marine) as the content of exchangeable Li and B is mineralogically controlled. The highest δ7Li and δ11B values are found in marine illite-rich samples and marine chlorite-rich samples, respectively.
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  • 57
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    International Association of Meteorology and Atmospheric Sciences (IAMAS)
    In:  IAMAS Annual Report
    Publication Date: 2020-02-12
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  • 58
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    In:  Izvestiya - Physics of the Solid Earth
    Publication Date: 2020-02-12
    Description: The coherent behavior of four parameters characterizing the global field of low-frequency (periods from 2 to 500 min) seismic noise is studied. These parameters include logarithmic variance, kurtosis (coefficient of excess), width of support of multifractal singularity spectrum, and minimal normalized entropy of the distribution of the squared orthogonal wavelet coefficients. The analy)sis is based on the data from 229 broadband stations of GSN, GEOSCOPE, and GEOFON networks for a 16-year period from the beginning of 1997 to the end of 2012. The entire set of stations is subdivided into eight groups, which, taken together, provide full coverage of the Earth. The daily median values of the studied noise parameters are calculated in each group. This procedure yields four 8-dimensional time series with a time step of 1 day with a length of 5844 samples in each scalar component. For each of the four 8-dimensional time series, the frequency-time diagram of the evolution of the spectral measure of coherence (based on canonical coherences) is constructed in the moving time window with a length of 365 days. Besides, for each parameter, the maximum-frequency values of the coherence measure and their mean over the four analyzed noise parameters are calculated as a measure of synchronization that depends on time only. Based on the conducted analysis, it is concluded that the increase in the intensity of the strongest (M ≥ 8.5) earthquakes after the mega-earthquake on Sumatra on December 26, 2004 was preceded by the enhancement of synchronization between the parameters of global seismic noise over the entire time interval of observations since the beginning of 1997. This synchronization continues growing up to the end of the studied period (2012), which can be interpreted as a probable precursor of the further increase in the intensity of the strongest earthquakes all over the world.
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  • 59
    Publication Date: 2020-02-12
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  • 60
    Publication Date: 2020-02-12
    Description: We present results from microseismic monitoring and geomechanical analysis obtained at the industrial-scale CO2 sequestration site at the In Salah gas development project in Algeria. More than 5000 microseismic events have been detected at a pilot monitoring well using a master event cross-correlation method. The microseismic activity occurs in four distinct clusters and thereof three clearly correlate with injection rates and wellhead pressures. These event clusters are consistent with a location within the reservoir interval. However, due to insufficient network geometry there are large uncertainties on event location. We estimate a fracture pressure of 155 bar (at the wellhead) from the comparison of injection pressure and injection rate and conclude that reservoir fracture pressure of the injection horizon has most likely been exceeded occasionally, accompanied by increased microseismic activity. Our analysis of 3-D ray tracing for direct and converted phases suggests that one of the event clusters is located at a shallower depth than the reservoir injection interval. However, this event cluster is most likely unrelated to changes in the injection activity at a single well, as the event times do not correlate with the wellhead pressures. Furthermore, this event cluster shows b-values close to one, indicating re-activated natural or tectonic seismicity on pre-existing weakness zones rather than injection induced seismicity. Analysis of event azimuths and significant shear wave splitting of up to 5 per cent provide further valuable insight into fluid migration and fracture orientation at the reservoir level. Although only one geophone was available during the critical injection period, the microseismic monitoring of CO2 injection at In Salah is capable of addressing some of the most relevant questions about fluid migration and reservoir integrity. An improved monitoring array with larger aperture and higher sensitivity is highly recommended, as it could greatly enhance the value of this technique. As such, real-time microseismic monitoring can be used to guide the injection pressure below fracture pressure, thus providing a tool to mitigate the risk of inducing felt seismicity and compromising seal integrity.
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  • 61
    Publication Date: 2020-02-12
    Description: In this study, SKS and local S phases are analyzed to investigate variations of shear-wave splitting parameters along two dense seismic profiles across the central Andean Altiplano and Puna plateaus. In contrast to previous observations, the vast majority of the measurements reveal fast polarizations sub-parallel to the subduction direction of the Nazca plate with delay times between 0.3 and 1.2 s. Local phases show larger variations of fast polarizations and exhibit delay times ranging between 0.1 and 1.1 s. Two 70 km and 100 km wide sections along the Altiplano profile exhibit larger delay times and are characterized by fast polarizations oriented sub-parallel to major fault zones. Based on finite-difference wavefield calculations for anisotropic subduction zone models we demonstrate that the observations are best explained by fossil slab anisotropy with fast symmetry axes oriented sub-parallel to the slab movement in combination with a significant component of crustal anisotropy of nearly trench-parallel fast-axis orientation. From the modeling we exclude a sub-lithospheric origin of the observed strong anomalies due to the short-scale variations of the fast polarizations. Instead, our results indicate that anisotropy in the Central Andes generally reflects the direction of plate motion while the observed trench-parallel fast polarizations likely originate in the continental crust above the subducting slab.
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  • 62
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    Deutsches GeoForschungsZentrum GFZ
    In:  Scientific Technical Report
    Publication Date: 2020-02-12
    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.
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  • 63
    Publication Date: 2020-02-12
    Language: English
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  • 64
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    In:  Journal of Physics : Conference Series
    Publication Date: 2020-02-12
    Description: The problem of monitoring of different types of seismic events – geoacoustic precursors of earthquakes, industrial and field explosions, places fragments fall of separating parts of rockets-carriers, etc. is one of the key in the modern ecology of the environment. The peculiarity of this kind of monitoring is that it is mobile seismic groups, which should be based in the proposed area of occurrence of events. One of the most important steps for solving the problems connected with the detection and identification of recorded data from passive sensors in mobile seismic array (MSA). The task of determining the nature of the source and its' coordinates lies in the basis of direction, referred to as the geoacoustic location. Using a new approach (not by location but by neural classification of waveform "portraits") usability of algorithm which based on quantitative parameters of signal will be demonstrated.
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  • 65
    Publication Date: 2020-02-12
    Description: After more than 4.5 years in orbit, the Gravity field and steady-state Ocean Circulation Explorer (GOCE) mission ended with the reentry of the satellite on 11 November 2013. This publication serves as a reference for the fifth gravity field model based on the time-wise approach (EGM_TIM_RL05), a global model only determined from GOCE observations. Due to its independence of any other gravity data, a consistent and homogeneous set of spherical harmonic coefficients up to degree and order 280 (corresponding to spatial resolution of 71.5km on ground) is provided including a full covariance matrix characterizing the uncertainties of the model. The associated covariance matrix realistically describes the model quality. It is the first model which is purely based on GOCE including all observations collected during the entire mission. The achieved mean global accuracy is 2.4cm in terms of geoid heights and 0.7mGal for gravity anomalies at a spatial resolution of 100km.
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  • 66
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    In:  New Manual of Seismological Observatory Practice 2 (NMSOP-2)
    Publication Date: 2020-02-12
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  • 67
    Publication Date: 2020-02-12
    Description: The Cyprean arc is considered to be a convergent boundary in the Eastern Mediterranean where the African plate is being subducted beneath the Anatolian plate. Mapping the lateral variations of seismic anisotropy parameters can provide essential hints to mantle dynamics and flow patterns in relation to the geometry and style of deformation developed under different pressure, temperature conditions around the subducting African lithosphere. In this study, seismic anisotropy parameters, fast polarization directions (ϕ) and delay times (δt) beneath the Cyprean arc and NE Mediterranean Sea are inferred from the shear wave splitting analysis performed on core-mantle refracted teleseismic shear waves (SKS phases). Earthquake data used in the present work are extracted from the continuous recordings of 8 broad-band seismic stations located in the study region for a time period during 1999 and 2012. The overall results exhibits clear evidences of mantle anisotropy with relatively uniform NE–SW aligned fast polarization directions. No abrupt changes in fast polarization directions (ϕ) are observed. However, near the Dead Sea Transform Fault, ϕ values tend to rotate from NE–SW to N–S and NW–SE in accordance with Pn anisotropy observations. Delay times (δt) vary between 0.61 s ± 0.10 s and 1.90 s ± 0.13 s. The range of delay times are generally consistent with those observed in the mantle rather than implying a crustal anisotropy. A predominant pattern of NNE–SSW fast polarization directions that is coherent with earlier SKS splitting measurements observed beneath north, central and East Anatolia suggests a SW directed asthenospheric flow caused by slab rollback process along the Hellenic and Cyprean arcs. Furthermore, apparent splitting parameters did not exhibit any significant directional dependence which may imply possibility of the presence of anisotropic models with two-layer anisotropy or dipping axis of symmetry beneath the northeast Mediterranean Sea and Cyprean arc. Consequently, a simple, single-layered and sub-horizontal anisotropy model is tentatively suggested for the study region.
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  • 68
    Publication Date: 2020-02-12
    Description: We study acoustic emissions (AEs) associated with shear and tensile failures around a horizontal borehole in a sandstone sample subjected to triaxial stress. The aim is to relate the AE event rate to macroscopic observations of sample deformation and the percentage of isotropic and deviatoric components of the seismic moment tensors to the expected failure mechanisms. The horizontal hole interferes with the applied load and forms a strongly spatially dependent anisotropic stress field, focusing the crack initiation into both shear and tensile failures. The recorded AEs follows reasonably well existing damage models, but the elastic solution of hoop stress does not represent the onset of failure around the borehole. The focal mechanisms correlate with the orientation of macroscopic fractures in the sample. Events close to the borehole show a higher fraction of isotropic percentage in moment tensors compared to events occurring in the macroscopic fracture featuring higher double-couple percentages. The inhomogeneous stress field due to the borehole and the stress induced damage is strongly affecting the axial and radial velocities which in turn affect the waveforms of the recorded AEs and the resulting moment tensors. The VP/VS ratio obtained from the ratio of isotropic to compensated linear vector dipole components of the moment tensors is close to that obtained from ultrasonic velocity measurements.
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  • 69
    Publication Date: 2020-02-12
    Description: The Tarutung Basin is located at a right step-over in the northern central segment of the dextral strike-slip Sumatran Fault System (SFS). Details of the fault structure along the Tarutung Basin are derived from the relocations of seismicity as well as from focal mechanism and structural geology. The seismicity distribution derived by a 3D inversion for hypocenter relocation is clustered according to a fault-like seismicity distribution. The seismicity is relocated with a double-difference technique (HYPODD) involving the waveform cross-correlations. We used 46,904 and 3191 arrival differences obtained from catalogue data and cross-correlation analysis, respectively. Focal mechanisms of events were analyzed by applying a grid search method (HASH code). Although there is no significant shift of the hypocenters (10.8 m in average) and centroids (167 m in average), the application of the double difference relocation sharpens the earthquake distribution. The earthquake lineation reflects the fault system, the extensional duplex fault system, and the negative flower structure within the Tarutung Basin. The focal mechanisms of events at the edge of the basin are dominantly of strike-slip type representing the dextral strike-slip Sumatran Fault System. The almost north–south striking normal fault events along extensional zones beneath the basin correlate with the maximum principal stress direction which is the direction of the Indo-Australian plate motion. The extensional zones form an en-echelon pattern indicated by the presence of strike-slip faults striking NE–SW to NW–SE events. The detailed characteristics of the fault system derived from the seismological study are also corroborated by structural geology at the surface.
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  • 70
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    In:  New Manual of Seismological Observatory Practice 2 (NMSOP-2)
    Publication Date: 2020-02-12
    Language: English
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  • 71
    Publication Date: 2020-02-12
    Description: Understanding the dynamics of subduction is critical to our overall understanding of plate tectonics and the solid Earth system. Observations of seismic anisotropy can yield constraints on deformation patterns in the mantle surrounding subducting slabs, providing a tool for studying subduction dynamics. While many observations of seismic anisotropy have been made in subduction systems, our understanding of the mantle beneath subducting slabs remains tenuous due to the difficulty of constraining anisotropy in the sub‐slab region. Recently, the source‐side shear wave splitting technique has been refined and applied to several subduction systems worldwide, making accurate and direct measurements of sub‐slab anisotropy feasible and offering unprecedented spatial and depth coverage in the sub‐slab mantle. Here we present source‐side shear wave splitting measurements for the Central America, Alaska‐Aleutians, Sumatra, Ryukyu, and Izu‐Bonin‐Japan‐Kurile subduction systems. We find that measured fast splitting directions in these regions generally fall into two broad categories, aligning either with the strike of the trench or with the motion of the subducting slab relative to the overriding plate. Trench parallel fast splitting directions dominate beneath the Izu‐Bonin, Japan, and southern Kurile slabs and part of the Sumatra system, while fast directions that parallel the motion of the downgoing plate dominate in the Ryukyu, Central America, northern Kurile, western Sumatra, and Alaska‐Aleutian regions. We find that plate motion parallel fast splitting directions in the sub‐slab mantle are more common than previously thought. We observe a correlation between fast direction and age of the subducting lithosphere; older lithosphere (〉95 Ma) is associated with trench parallel splitting while younger lithosphere (〈95 Ma) is associated with plate motion parallel fast splitting directions. Finally, we observe source‐side splitting for deep earthquakes (transition zone depths) beneath Japan and Sumatra, suggesting the presence of anisotropy at midmantle depths beneath these regions.
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  • 72
    Publication Date: 2020-02-12
    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.
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  • 73
    Publication Date: 2020-02-12
    Description: We present an analysis and characterization of the regional seismicity recorded by a temporary broadband seismic network deployed in the Cape Verde archipelago between November 2007 and September 2008. The detection of earthquakes was based on spectrograms, allowing the discrimination from low-frequency volcanic signals, resulting in 358 events of which 265 were located, the magnitudes usually being smaller than 3. For the location, a new 1-D P-velocity model was derived for the region showing a crust consistent with an oceanic crustal structure. The seismicity is located mostly offshore the westernmost and geologically youngest areas of the archipelago, near the islands of Santo Antão and São Vicente in the NW and Brava and Fogo in the SW. The SW cluster has a lower occurrence rate and corresponds to seismicity concentrated mainly along an alignment between Brava and the Cadamosto seamount presenting normal faulting mechanisms. The existence of the NW cluster, located offshore SW of Santo Antão, was so far unknown and concentrates around a recently recognized submarine cone field; this cluster presents focal depths extending from the crust to the upper mantle and suggests volcanic unrest. No evident temporal behaviour could be perceived, although the events tend to occur in bursts of activity lasting a few days. In this recording period, no significant activity was detected at Fogo volcano, the most active volcanic edifice in Cape Verde. The seismicity characteristics point mainly to a volcanic origin. The correlation of the recorded seismicity with active volcanic structures agrees with the tendency for a westward migration of volcanic activity in the archipelago as indicated by the geologic record.
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  • 74
    Publication Date: 2020-02-12
    Description: We image the lithospheric and upper asthenospheric structure of western continental Yemen with 24 broadband stations to evaluate the role of the Afar plume on the evolution of the continental margin and its extent eastward along the Gulf of Aden. We use teleseismic tomography to compute relative P wave velocity variations in south‐western Yemen down to 300 km depth. Published receiver function analysis suggest a dramatic and localized thinning of the crust in the vicinity of the Red Sea and the Gulf of Aden, consistent with the velocity structure that we retrieve in our model. The mantle part of the model is dominated by the presence of a low‐velocity anomaly in which we infer partial melting just below thick Oligocene flood basalts and recent off‐axis volcanic events (from 15 Ma to present). This low‐velocity anomaly could correspond to an abnormally hot mantle and could be responsible for dynamic topography and recent magmatism in western Yemen. Our new P wave velocity model beneath western Yemen suggests the young rift flank volcanoes beneath margins and on the flanks of the Red Sea rift are caused by focused small‐scale diapiric upwelling from a broad region of hot mantle beneath the area. Our work shows that relatively hot mantle, along with partial melting of the mantle, can persist beneath rifted margins after breakup has occurred.
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  • 75
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    In:  Journal of Geophysical Research
    Publication Date: 2020-02-12
    Description: New findings of the structure of the Dead Sea sedimentary basin and its eastern and western bordering regions are obtained by P and PKP wave relative traveltime residuals of 644 teleseisms, as recorded by the Dead Sea Integrated Research portable seismic network in the Dead Sea basin and its neighboring regions. The Lisan Peninsula is characterized by relatively small teleseismic traveltime residuals of about 0.14 s, in the latitude range of 31.22°–31.37° and at the longitude of 35.50°, slowly decreasing toward the west. The largest teleseismic traveltime residuals are in the southern Dead Sea basin, south of the Lisan Peninsula in the latitude range of 31.05°–31.15° and along longitude 35.45° and continuing southward toward the Amaziahu Fault, reaching values of 0.4–0.5 s. There is a small positive residual at the Amaziahu Fault and a small negative residual south of it probably marking the southern end of the Dead Sea basin. East and west of the Dead Sea basin the mean teleseismic traveltime residuals are negative with overall averages of −0.35 s and −0.45 s, respectively. Using the teleseismic residuals, we estimate the horizontal dimensions of the Lisan salt diapir to be 23 km × 13 km at its widest and a maximal thickness of about 7.2 km. The thickness of the Mount Sodom salt diapir is estimated as 6.2 km.
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  • 76
    Publication Date: 2020-02-12
    Description: The voluminous ash-flow eruptive products in the Central Andes imply that there are major magma bodies; however, how these magma bodies develop and change in time and space are not understood. In this study, we analyse the deformation activity of the Uturuncu Volcano, SW Bolivia, from 2003 to 2009 using a satellite radar interferometry (InSAR) data set. We find that the strength and the pattern of the present deformation can be explained by a pressurized source, such as an inflating flat-topped magma body at ∼22 ± 9 km depth below the surface. Furthermore, we examine the optical remote sensing data to perform a lineament analysis, which shows in a geographic information system (GIS) that a girdle of river streams and faults encircle the volcano at radial distance of approximately 15 km. Using numerical stress models, we locate a magma body beneath the volcano and find that the lineaments are best explained by a deflating flat-topped magma body at approximately 18 ± 2 km depth, which is consistent with the InSAR study. Thus, both the independent analysis of InSAR and lineament data suggest the presence of a horizontally extended, flat-topped magma body beneath Uturuncu. The location depth is in agreement with, or just above, a prominent seismic low velocity zone. Consequently, although the sign of deformation caused by the herein constrained magma body differs, the similar geometry and similar location suggest them to be similar, possibly indicating longevity of a magma storage region.
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  • 77
    Publication Date: 2020-02-12
    Language: English
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  • 78
    Publication Date: 2020-02-12
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  • 79
    Publication Date: 2020-02-12
    Description: Earthquake hypocenters recorded in the Andean Southern Puna seismic array (25–28°S, 70–65°W) provide new constraints on the shape of the subducting Nazca plate beneath the Puna plateau, the transition into the Chilean‐Pampean flat slab and the thermal state of the mantle and crust. Some 270 new mantle hypocenters suggest that the subducting slab under the Puna shoals into the flat‐slab segment more abruptly and farther to the north than previously indicated. The revised geometry is consistent with the Central Volcanic Zone Incapillo caldera being the southernmost center with Pleistocene activity until reaching the southern side of the flat‐slab region. Evidence for the revised slab geometry includes three well‐defined hypocenter clusters in the Pipanaco nest (27.5–29°S, 68–66°W), which are interpreted to reflect slab‐bending stresses. A few low‐magnitude earthquakes with strongly attenuated S waves in the long‐recognized Antofalla teleseismic gap (25.5–27.5°S) support a continuous slab under the Southern Puna. The paucity of gap earthquakes and the presence of mafic magmas are consistent with a hot mantle wedge reflecting recent lithospheric delamination. Evidence for a hot overlaying Puna crust comes from new crustal earthquake hypocenters concentrated at depths shallower than 5 km. Two notable short‐duration swarms were recorded under the resurgent dome of the ~2 Ma back‐arc Cerro Galán caldera and the near‐arc Cerro Torta dome. New crustal earthquake focal mechanisms from 17 events in the array along with two existing mechanisms have strike slip, oblique reverse, and oblique normal solutions fitting with regional E‐W compression and N‐S extension.
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  • 80
    Publication Date: 2020-02-12
    Description: Gravity gradient measurements from ESA's satellite mission Gravity field and steady-state Ocean Circulation Explorer (GOCE) contain significant high- and mid-frequency signal components, which are primarily caused by the attraction of the Earth's topographic and isostatic masses. In order to mitigate the resulting numerical instability of a harmonic downward continuation, the observed gradients can be smoothed with respect to topographic-isostatic effects using a remove-compute-restore technique. For this reason, topographic-isostatic reductions are calculated by forward modeling that employs the advanced Rock-Water-Ice methodology. The basis of this approach is a three-layer decomposition of the topography with variable density values and a modified Airy-Heiskanen isostatic concept incorporating a depth model of the MohoroviiA double dagger discontinuity. Moreover, tesseroid bodies are utilized for mass discretization and arranged on an ellipsoidal reference surface. To evaluate the degree of smoothing via topographic-isostatic reduction of GOCE gravity gradients, a wavelet-based assessment is presented in this paper and compared with statistical inferences in the space domain. Using the Morlet wavelet, continuous wavelet transforms are applied to measured GOCE gravity gradients before and after reducing topographic-isostatic signals. By analyzing a representative data set in the Himalayan region, an employment of the reductions leads to significantly smoothed gradients. In addition, smoothing effects that are invisible in the space domain can be detected in wavelet scalograms, making a wavelet-based spectral analysis a powerful tool.
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  • 81
    Publication Date: 2020-02-12
    Language: English
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  • 82
    Publication Date: 2020-02-12
    Description: GeoMod is a biennial conference dedicated to latest results of analogue and numerical modelling of lithospheric and mantle deformation. GeoMod2014 focussed on rheology and deformation at a wide range of temporal and spatial scales: from earthquakes to long-term deformation, from micro-structures to orogens and subduction systems, as well as volcanotectonics and the interaction between tectonics and surface processes. GeoMod2014 took place at the Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences from 31 August to 3 September 2014. The conference was followed by two two-days short courses on different modelling techniques.The scientific programme of GeoMod2014 conference was organized in seven topical sessions over 3 days. The proceedings are composed of extended abstracts from all oral and poster contribution that were presented during the conferenvce. In addition to the full version of the Proceedings, and to provide smaller sized files for download, we also provide sub-volumes for each session. Each sub-volume contains the full table of content and authors index. The names of the sessions are also given in the filenames.
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  • 83
    Publication Date: 2020-02-12
    Description: We present a three-dimensional model of shear wave velocity for the upper mantle of China and the surrounding region by analyzing 50,338 vertical component multi-mode Rayleigh wave seismograms, recorded at 144 permanent and more than 300 temporary broadband stations in and around China. The procedure involves combination of 1-D path average models obtained by modeling each Rayleigh waveform up to the 4th higher mode in a tomographic inversion scheme. The dense station network and the use of multi-mode analysis help to achieve a lateral resolution of a few hundred kilometers down to 400 km depth. The seismic lithosphere, as it is defined by the crust and the high velocity mantle lid, is to the first order thin in east China and thick in the west, with a high velocity lid extending down to about 200 km depth beneath much of the Tibet–Pamir plateau. Beneath India, the thickness of the seismic lithosphere gradually increases from ~ 100 km in south India to more than 150 km in north India, where it underthrusts the Tibetan plateau to approximately the Jinsha River Suture. High velocity lid extending down to 100–150 km depth is also observed in the Tarim basin, Sichuan basin and Ordos block. In the eastern part of the North China craton the seismic lithosphere is probably close to or thinner than 70 km. Adjacent to these areas, the high velocity lid in the eastern Yangtze craton and South China fold system extends down to 70–80 km depth. A large-scale subhorizontal high velocity body is observed at depths of 150–350 km beneath the entire east China cratonic areas. This high velocity body might be the remnant of a delamination process which resulted in the decratonization of the North China and the Yangtze cratons.
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  • 84
    Publication Date: 2020-02-12
    Description: The southern Puna Plateau has been proposed to result from a major Pliocene delamination event that has previously been inferred from geochemical, geological, and some preliminary geophysical data. Seventy-five seismic stations were deployed across the southern Puna Plateau in 2007–2009 by scientists fromthe U.S., Germany, Chile, and Argentina to test the delamination model for the region. The Puna passive seismic stations were located between 25 and 28°S. Using the seismic waveform data collected from the PUNA experiment,we employ attenuation tomography methods to resolve both compressional and shear quality factors (Qp and Qs, respectively) in the crust and uppermost mantle. The images clearly show a high-Q Nazca slab subducting eastward beneath the Puna plateau and another high-Q block with a westward dip beneath the Eastern Cordillera. We suggest that the latter is a piece of delaminated South American lithosphere. A significant low-Q zone lies between the Nazca slab and the South American lithosphere and extends southward from the northernmargin of the seismic array at 25°S before vanishing around 27.5°S. This low-Q zone extends farther west in the crust and uppermost mantle at the southern end of the seismic array. The low-Q zone reaches ~100 km depth beneath the northern part of the array but only ~50 km depth in the south. Lateral variations of the low-Q zone reflect the possible mechanism conversion between mantle upwelling related to delamination and dehydration. The depth of the Nazca slab as defined by Q images decreases from north to south beneath the plateau, which is consistentwith the steep-flat transition of the angle of the subducting slab as defined by previous earthquake studies.
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  • 85
    Publication Date: 2020-02-12
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  • 86
    Publication Date: 2020-02-12
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  • 87
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    Deutsches GeoForschungsZentrum GFZ
    In:  Scientific Technical Report
    Publication Date: 2020-02-12
    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.
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  • 88
    Publication Date: 2020-02-12
    Description: The seismic gap theory1 identifies regions of elevated hazard based on a lack of recent seismicity in comparison with other portions of a fault. It has successfully explained past earthquakes (see, for example, ref. 2) and is useful for qualitatively describing where large earthquakes might occur. A large earthquake had been expected in the subduction zone adjacent to northern Chile3, 4, 5, 6, which had not ruptured in a megathrust earthquake since a M ~8.8 event in 1877. On 1 April 2014 a M 8.2 earthquake occurred within this seismic gap. Here we present an assessment of the seismotectonics of the March–April 2014 Iquique sequence, including analyses of earthquake relocations, moment tensors, finite fault models, moment deficit calculations and cumulative Coulomb stress transfer. This ensemble of information allows us to place the sequence within the context of regional seismicity and to identify areas of remaining and/or elevated hazard. Our results constrain the size and spatial extent of rupture, and indicate that this was not the earthquake that had been anticipated. Significant sections of the northern Chile subduction zone have not ruptured in almost 150 years, so it is likely that future megathrust earthquakes will occur to the south and potentially to the north of the 2014 Iquique sequence.
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  • 89
    Publication Date: 2020-02-12
    Description: This study performed the first assessment of the volcanic gas output from the Central Volcanic Zone (CVZ) of northern Chile. We present the fluxes and compositions of volcanic gases (H2O, CO2, H2, HCl, HF, and HBr) from five of the most actively degassing volcanoes in this region—Láscar, Lastarria, Putana, Ollagüe, and San Pedro—obtained during field campaigns in 2012 and 2013. The inferred gas plume compositions for Láscar and Lastarria (CO2/Stot = 0.9–2.2; Stot/HCl = 1.4–3.4) are similar to those obtained in the Southern Volcanic Zone of Chile, suggesting uniform magmatic gas fingerprint throughout the Chilean arc. Combining these compositions with our own UV spectroscopy measurements of the SO2 output (summing to ~1800 t d−1 for the CVZ), we calculate a cumulative CO2 output of 1743–1988 t d−1 and a total volatiles output of 〉20,200 t d−1.
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  • 90
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    In:  Izvestiya - Physics of the Solid Earth
    Publication Date: 2020-02-12
    Description: The method of surface-wave amplitude spectra inversion for the seismic moment tensor (SMT) is implemented and tested in the Pribaikalye region. The SMTs are calculated for 39 events with M w = 4.4–6.3, which occurred in the region in 2000–2011. Based on the obtained data, the seismotectionic deformations of the crust are estimated in two seismically active areas-the Northern Pribaikalye and northeastern Baikal rift zone. It is found that on a level of moderate-magnitude events, the region is dominated by the regimes of subhorizontal northwestern extension and strike-slip faulting, which reflects the long-term trends in the stress field of the crust in these parts of the rift.
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  • 91
    Publication Date: 2020-02-12
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  • 92
    Publication Date: 2020-02-12
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  • 93
    Publication Date: 2022-06-16
    Description: The research presented in this thesis was conducted at the Department of Earth Science, University of Bergen (Norway), and in parallel at the Institute of Earth Sciences, Joseph Fourier University (Grenoble, France) under the supervision of Prof. Ritske Huismans, Prof. Peter van der Beek and Prof. Haakon Fossen. The project started in September 2009 and was funded by the Norwegian Research Council through the Norwegian component of the European Science Foundation Eurocore TOPO-Europe project PyrTec. The computationally intensive numerical modeling was carried out on the University of Bergen supercomputers Fimm and Hexagon, maintained by the Bergen Center of Computational Science. The thesis is structured in accordance with the Norwegian guidelines for doctoral dissertations in natural sciences, where the main body of the thesis consists of research papers either published, submitted or about to be submitted to international peer-reviewed journals. The present thesis comprises three papers: Paper 1 has been accepted for publication by the AGU journal Tectonics; Paper 2 has been submitted to Earth and Planetary Science Letters; and Paper 3 has been submitted to the Journal of Geophysical Research. The three research papers are preceded by an Introductory Chapter that details the general background and aims of the project, synthesizes its outcome, and outlines prospects for future work. An authorship statement provides an overview of the contribution of each author to this collaborative research work.
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  • 94
    Publication Date: 2022-06-16
    Description: We present a new method that can be used to quantitatively evaluate the consistency between balanced section restorations and thermochronological data sets from orogenic belts. We have applied our method to a crustal-scale area-balanced cross-section restoration along a profile in the Central Pyrenees. This restoration is well constrained and supported by a wide variety of geological and geophysical data. Moreover, an extensive thermochronological data set has been collected independently in the area. We use the structural-kinematic software 2D-Move™ to constrain a set of velocity fields that describes the kinematics of the Central Pyrenees. Using these velocity fields as input for the thermokinematic code PECUBE, we derive predictions of the thermal history and a range of thermochronometric ages for the modeled area. We find that the kinematic history of the belt as inferred from section balancing is in good agreement with the published thermochronological data. High-temperature (zircon fission-track and K-feldspar Ar-Ar) data constrain the thermal structure of the belt as well as the timing of underplating. Low-temperature (apatite fission-track and (U-Th)/He) data require late synorogenic sedimentary burial of the southern flank of the Pyrenees between late Eocene (40 Ma) to late Miocene (9 Ma) times, consistent with previous studies, and imply that no such burial occurred on the northern flank.
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  • 95
    Publication Date: 2022-06-16
    Description: Surface processes and inherited structures are widely regarded as factors that strongly influence the evolution of mountain belts. The first-order effects of these parameters have been studied extensively throughout the last decades, but their relative importance remains notoriously difficult to assess and document. We use lithospheric scale plane-strain thermomechanical model experiments to study the effects of surface processes and extensional inheritance on the internal structure of contractional orogens and their foreland basins. Extensional inheritance is modeled explicitly by forward modeling the formation of a rift basin before reversing the velocity boundary conditions to model its inversion. Surface processes are modeled through the combination of a simple sedimentation algorithm, where all negative topography is filled up to a prescribed reference level, and an elevation-dependent erosion model. Our results show that (1) extensional inheritance facilitates the propagation of basement deformation in the retro-wedge and (2) increases the width of the orogen; (3) sedimentation increases the length scale of both thin-skinned and thick-skinned thrust sheets and (4) results in a wider orogen; (5) erosion helps to localize deformation resulting in a narrower orogen and a less well-developed retro-wedge. A comparison of the modeled behaviors to the High Atlas, the Pyrenees, and the Central Alps, three extensively studied natural examples characterized by different degrees of inversion, is presented and confirms the predicted controls of surface processes and extensional inheritance on orogenic structure.
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  • 96
    Publication Date: 2020-02-12
    Description: Located in the central Andes, the Altiplano-Puna Volcanic Complex (APVC) is the location of an 11–1 Ma silicic volcanic field, one of the largest and youngest on Earth. Yet its magmatic/plutonic underpinnings have been seismically investigated in only a few widely spaced locations. Previous studies have identified an extensive (∼60,000 km2) low-velocity zone (LVZ) below the APVC referred to as the Altiplano-Puna Magma Body (APMB); however, insufficient seismic constraints have precluded uniquely measuring its thickness, and the volume of the APMB remains mostly constrained by varying estimates of plutonic to volcanic (P:V) ratios. Here we present new 3-D seismic images of the APVC crust based on a joint inversion of Rayleigh-wave dispersion from ambient seismic noise and P-wave receiver functions from broadband seismic stations recently deployed in the area. We identify a large ∼200 km diameter and ∼11 km thick LVZ that we interpret as the plutonic complex that sourced the voluminous APVC volcanics and show that its volume is much larger than previous estimates, perhaps as much as an order of magnitude larger. The large volume (∼500,000 km3) and shallow depth (4–25 km below sea level) of the LVZ centered on the observed surface uplift below the composite volcano Uturuncu provide strong evidence linking our imaged low-velocity body (APMB) with the presence of an amalgamated plutonic complex. We suggest the APMB retains a significant percentage (up to 25%) of partial melt, most likely in a melt-crystal mush state, and is related to the source of the continued ground deformation attributed to magma ascent beneath the APVC. The seismic imaging of this plutonic complex and the well-preserved and documented volcanic deposits allow us to make one of the best-constrained calculations of a plutonic to volcanic ratio. Although this calculation is still dependent on a few critical assumptions, the large volume of the newly imaged APMB requires a much larger ratio (20–35) than often cited in the literature. This large ratio has significant implications for both petrologic and tectonic models of this portion of the Andean arc.
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  • 97
    Publication Date: 2020-02-12
    Description: On 1 April 2014, Northern Chile was struck by a magnitude 8.1 earthquake following a protracted series of foreshocks. The Integrated Plate Boundary Observatory Chile monitored the entire sequence of events, providing unprecedented resolution of the build-up to the main event and its rupture evolution. Here we show that the Iquique earthquake broke a central fraction of the so-called northern Chile seismic gap, the last major segment of the South American plate boundary that had not ruptured in the past century1,2. Since July 2013 three seismic clusters, each lasting a few weeks, hit this part of the plate boundary with earthquakes of increasing peak magnitudes. Starting with the second cluster, geodetic observations show surface displacements that can be associated with slip on the plate interface. These seismic clusters and their slip transients occupied a part of the plate interface that was transitional between a fully locked and a creeping portion. Leading up to this earthquake, the b value of the foreshocks gradually decreased during the years before the earthquake, reversing its trend a few days before the Iquique earthquake. The mainshock finally nucleated at the northern end of the foreshock area, which skirted a locked patch, and ruptured mainly downdip towards higher locking. Peak slip was attained immediately downdip of the foreshock region and at the margin of the locked patch. We conclude that gradual weakening of the central part of the seismic gap accentuated by the foreshock activity in a zone of intermediate seismic coupling was instrumental in causing final failure, distinguishing the Iquique earthquake from most great earthquakes. Finally, only one-third of the gap was broken and the remaining locked segments now pose a significant, increased seismic hazard with the potential to host an earthquake with a magnitude of 〉8.5.
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  • 98
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    Univ.
    In:  Dissertations from the Department of Physical Geography and Quaternary Geology
    Publication Date: 2020-02-12
    Language: English
    Type: info:eu-repo/semantics/doctoralThesis
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  • 99
    Publication Date: 2020-02-12
    Description: We analyzed the waveforms of the small- to moderate-sized earthquakes that took place in the northern part of the inner Isparta Angle (IA) to retrieve their source parameters and combine these results with the focal mechanism solutions of the larger events that occurred in 2007 in Eğirdir Lake at the apex of IA. In total, source mechanisms of 20 earthquakes within the magnitude range 3.5 〈 M 〈 5.0 were calculated using a regional moment tensor inversion technique. The inversion of the focal mechanisms yields an extensional regime with a NNE–SSW (N38°E) trending σ 3 axis. Inversion results are related to a mainly WNW–ESE oriented normal fault beneath Eğirdir Lake. The R value of a NNE–SSW extensional regime is 0.562 showing a triaxial stress state in the region. The current stress regime results from complex subduction processes such as slab pull, slab break-off, roll-back and/or retreating mechanism along the Hellenic and Cyprus arcs and the southwestward extrusion of the Anatolian block since the early Pliocene.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 100
    Publication Date: 2020-02-12
    Description: We obtained high-precision locations for 5250 earthquakes in the Iquique segment of the northern Chilean subduction zone from two temporary local seismic networks around 21°S. A double seismic zone in the downgoing Nazca slab can be clearly identified. One band of seismicity is located at the plate interface and a second one 20–25 km deeper in the oceanic mantle. It can be traced updip to uncommonly shallow levels of 50 km. A combined interpretation of seismicity and reflectivity along the seismic ANCORP’96 experiment suggests the prevalence of fluid processes in the subducted oceanic crust as well as in the uppermost 20 km of the mantle. Crustal seismicity is pervasive below the Coastal Cordillera. Beneath the Precordillera, the lower bound of crustal seismicity delineates a sharp west-dipping boundary down to 20 km depth, consistent with earlier findings indicating a rheological boundary.
    Language: English
    Type: info:eu-repo/semantics/article
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