TY - JOUR A1 - Rajabi, Mojtaba A1 - Ziegler, Moritz O. A1 - Tingay, Mark A1 - Heidbach, Oliver A1 - Reynolds, Scott T1 - Contemporary tectonic stress pattern of the Taranaki Basin, New Zealand JF - Journal of geophysical research : Solid earth N2 - The present-day stress state is a key parameter in numerous geoscientific research fields including geodynamics, seismic hazard assessment, and geomechanics of georeservoirs. The Taranaki Basin of New Zealand is located on the Australian Plate and forms the western boundary of tectonic deformation due to Pacific Plate subduction along the Hikurangi margin. This paper presents the first comprehensive wellbore-derived basin-scale in situ stress analysis in New Zealand. We analyze borehole image and oriented caliper data from 129 petroleum wells in the Taranaki Basin to interpret the shape of boreholes and determine the orientation of maximum horizontal stress (S-Hmax). We combine these data (151 S-Hmax data records) with 40 stress data records derived from individual earthquake focal mechanism solutions, 6 from stress inversions of focal mechanisms, and 1 data record using the average of several focal mechanism solutions. The resulting data set has 198 data records for the Taranaki Basin and suggests a regional S-Hmax orientation of N068 degrees E (22 degrees), which is in agreement with NW-SE extension suggested by geological data. Furthermore, this ENE-WSW average S-Hmax orientation is subparallel to the subduction trench and strike of the subducting slab (N50 degrees E) beneath the central western North Island. Hence, we suggest that the slab geometry and the associated forces due to slab rollback are the key control of crustal stress in the Taranaki Basin. In addition, we find stress perturbations with depth in the vicinity of faults in some of the studied wells, which highlight the impact of local stress sources on the present-day stress rotation. KW - in situ stress KW - Taranaki Basin KW - New Zealand KW - plate tectonics KW - subduction zone Y1 - 2016 U6 - https://doi.org/10.1002/2016JB013178 SN - 2169-9313 SN - 2169-9356 VL - 121 SP - 6053 EP - 6070 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Ziegler, Moritz O. A1 - Rajabi, Mojtaba A1 - Heidbach, Oliver A1 - Hersir, Gylfi Pall A1 - Agustsson, Kristjan A1 - Arnadottir, Sigurveig A1 - Zang, Arno T1 - The stress pattern of Iceland JF - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth N2 - Iceland is located on the Mid-Atlantic Ridge which is the plate boundary between the Eurasian and the North American plates. It is one of the few places on earth where an active spreading centre is located onshore but the stress pattern has not been extensively investigated so far. In this paper we present a comprehensive compilation of the orientation of maximum horizontal stress (S-Hmax). In particular we interpret borehole breakouts and drilling induced fractures from borehole image logs in 57 geothermal wells onshore Iceland. The borehole results are combined with other stress indicators including earthquake focal mechanism solutions, geological information and overcoring measurements resulting in a dataset with 495 data records for the S-Hmax orientation. The reliability of each indicator is assessed according to the quality criteria of the World Stress Map project The majority of S-Hmax orientation data records in Iceland is derived from earthquake focal mechanism solutions (35%) and geological fault slip inversions (26%). 20% of the data are borehole related stress indicators. In addition minor shares of S-Hmax orientations are compiled, amongst others, from focal mechanism inversions and the alignment of fissure eruptions. The results show that the S-Hmax orientations derived from different depths and stress indicators are consistent with each other. The resulting pattern of the present-day stress in Iceland has four distinct subsets of S-Hmax orientations. The S-Hmax orientation is parallel to the rift axes in the vicinity of the active spreading regions. It changes from NE-SW in the South to approximately N-S in central Iceland and NNW-SSE in the North. In the Westfjords which is located far away from the ridge the regional S-Hmax rotates and is parallel to the plate motion. (C) 2016 Elsevier B.V. All rights reserved. KW - Iceland KW - Stress field KW - Stress pattern KW - Borehole image logs Y1 - 2016 U6 - https://doi.org/10.1016/j.tecto.2016.02.008 SN - 0040-1951 SN - 1879-3266 VL - 674 SP - 101 EP - 113 PB - Elsevier CY - Amsterdam ER - TY - GEN A1 - Gholamrezaie, Ershad A1 - Scheck-Wenderoth, Magdalena A1 - Bott, Judith A1 - Heidbach, Oliver A1 - Strecker, Manfred T1 - 3-D crustal density model of the Sea of Marmara T2 - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe N2 - Abstract. The Sea of Marmara, in northwestern Turkey, is a transition zone where the dextral North Anatolian Fault zone (NAFZ) propagates westward from the Anatolian Plate to the Aegean Sea Plate. The area is of interest in the context of seismic hazard of Istanbul, a metropolitan area with about 15 million inhabitants. Geophysical observations indicate that the crust is heterogeneous beneath the Marmara basin, but a detailed characterization of the crustal heterogeneities is still missing. To assess if and how crustal heterogeneities are related to the NAFZ segmentation below the Sea of Marmara, we develop new crustal-scale 3-D density models which integrate geological and seismological data and that are additionally constrained by 3-D gravity modeling. For the latter, we use two different gravity datasets including global satellite data and local marine gravity observation. Considering the two different datasets and the general non-uniqueness in potential field modeling, we suggest three possible “end-member” solutions that are all consistent with the observed gravity field and illustrate the spectrum of possible solutions. These models indicate that the observed gravitational anomalies originate from significant density heterogeneities within the crust. Two layers of sediments, one syn-kinematic and one pre-kinematic with respect to the Sea of Marmara formation are underlain by a heterogeneous crystalline crust. A felsic upper crystalline crust (average density of 2720 kgm⁻³) and an intermediate to mafic lower crystalline crust (average density of 2890 kgm⁻³) appear to be cross-cut by two large, dome-shaped mafic highdensity bodies (density of 2890 to 3150 kgm⁻³) of considerable thickness above a rather uniform lithospheric mantle (3300 kgm⁻³). The spatial correlation between two major bends of the main Marmara fault and the location of the highdensity bodies suggests that the distribution of lithological heterogeneities within the crust controls the rheological behavior along the NAFZ and, consequently, maybe influences fault segmentation and thus the seismic hazard assessment in the region. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 737 KW - North Anatolian Fault KW - Shear Zone KW - Northwestern Anatolia KW - Geomechanical Model KW - Tectonic Evolution KW - Slip Distribution KW - Middle Strand KW - Pull-Apart KW - Long-Term KW - NW Turkey Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-434661 SN - 1866-8372 IS - 737 SP - 785 EP - 807 ER - TY - JOUR A1 - Gholamrezaie, Ershad A1 - Scheck-Wenderoth, Magdalena A1 - Bott, Judith A1 - Heidbach, Oliver A1 - Strecker, Manfred T1 - 3-D crustal density model of the Sea of Marmara JF - Solid Earth N2 - Abstract. The Sea of Marmara, in northwestern Turkey, is a transition zone where the dextral North Anatolian Fault zone (NAFZ) propagates westward from the Anatolian Plate to the Aegean Sea Plate. The area is of interest in the context of seismic hazard of Istanbul, a metropolitan area with about 15 million inhabitants. Geophysical observations indicate that the crust is heterogeneous beneath the Marmara basin, but a detailed characterization of the crustal heterogeneities is still missing. To assess if and how crustal heterogeneities are related to the NAFZ segmentation below the Sea of Marmara, we develop new crustal-scale 3-D density models which integrate geological and seismological data and that are additionally constrained by 3-D gravity modeling. For the latter, we use two different gravity datasets including global satellite data and local marine gravity observation. Considering the two different datasets and the general non-uniqueness in potential field modeling, we suggest three possible “end-member” solutions that are all consistent with the observed gravity field and illustrate the spectrum of possible solutions. These models indicate that the observed gravitational anomalies originate from significant density heterogeneities within the crust. Two layers of sediments, one syn-kinematic and one pre-kinematic with respect to the Sea of Marmara formation are underlain by a heterogeneous crystalline crust. A felsic upper crystalline crust (average density of 2720 kgm⁻³) and an intermediate to mafic lower crystalline crust (average density of 2890 kgm⁻³) appear to be cross-cut by two large, dome-shaped mafic highdensity bodies (density of 2890 to 3150 kgm⁻³) of considerable thickness above a rather uniform lithospheric mantle (3300 kgm⁻³). The spatial correlation between two major bends of the main Marmara fault and the location of the highdensity bodies suggests that the distribution of lithological heterogeneities within the crust controls the rheological behavior along the NAFZ and, consequently, maybe influences fault segmentation and thus the seismic hazard assessment in the region. KW - North Anatolian Fault KW - Shear Zone KW - Northwestern Anatolia KW - Geomechanical Model KW - Tectonic Evolution KW - Slip Distribution KW - Middle Strand KW - Pull-Apart KW - Long-Term KW - NW Turkey Y1 - 2019 U6 - https://doi.org/10.5194/se-10-785-2019 SN - 1869-9510 SN - 1869-9529 VL - 10 SP - 785 EP - 807 PB - Copernicus Publ. CY - Göttingen ER - TY - GEN A1 - Ziegler, Moritz O. A1 - Heidbach, Oliver A1 - Reinecker, John A1 - Przybycin, Anna M. A1 - Scheck-Wenderoth, Magdalena T1 - A multi-stage 3-D stress field modelling approach exemplified in the Bavarian Molasse Basin T2 - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe N2 - The knowledge of the contemporary in situ stress state is a key issue for safe and sustainable subsurface engineering. However, information on the orientation and magnitudes of the stress state is limited and often not available for the areas of interest. Therefore 3-D geomechanical-numerical modelling is used to estimate the in situ stress state and the distance of faults from failure for application in subsurface engineering. The main challenge in this approach is to bridge the gap in scale between the widely scattered data used for calibration of the model and the high resolution in the target area required for the application. We present a multi-stage 3-D geomechanical-numerical approach which provides a state-of-the-art model of the stress field for a reservoir-scale area from widely scattered data records. Therefore, we first use a large-scale regional model which is calibrated by available stress data and provides the full 3-D stress tensor at discrete points in the entire model volume. The modelled stress state is used subsequently for the calibration of a smaller-scale model located within the large-scale model in an area without any observed stress data records. We exemplify this approach with two-stages for the area around Munich in the German Molasse Basin. As an example of application, we estimate the scalar values for slip tendency and fracture potential from the model results as measures for the criticality of fault reactivation in the reservoir-scale model. The modelling results show that variations due to uncertainties in the input data are mainly introduced by the uncertain material properties and missing S-Hmax magnitude estimates needed for a more reliable model calibration. This leads to the conclusion that at this stage the model's reliability depends only on the amount and quality of available stress information rather than on the modelling technique itself or on local details of the model geometry. Any improvements in modelling and increases in model reliability can only be achieved using more high-quality data for calibration. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 556 KW - in-situ stress KW - induced seismicity KW - geothermal-reservoirs KW - geomechanical model KW - fault reactivation KW - alpine foreland KW - map project KW - km depth KW - orientation KW - system Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-409806 SN - 1866-8372 IS - 556 ER - TY - JOUR A1 - Ziegler, Moritz O. A1 - Heidbach, Oliver A1 - Reinecker, John A1 - Przybycin, Anna M. A1 - Scheck-Wenderoth, Magdalena T1 - A multi-stage 3-D stress field modelling approach exemplified in the Bavarian Molasse Basin JF - Solid earth Y1 - 2016 U6 - https://doi.org/10.5194/se-7-1365-2016 SN - 1869-9510 SN - 1869-9529 VL - 7 SP - 1365 EP - 1382 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - von Specht, Sebastian A1 - Heidbach, Oliver A1 - Cotton, Fabrice A1 - Zang, Arno T1 - Uncertainty reduction of stress tensor inversion with data-driven catalogue selection JF - Geophysical journal international N2 - The selection of earthquake focal mechanisms (FMs) for stress tensor inversion (STI) is commonly done on a spatial basis, that is, hypocentres. However, this selection approach may include data that are undesired, for example, by mixing events that are caused by different stress tensors when for the STI a single stress tensor is assumed. Due to the significant increase of FM data in the past decades, objective data-driven data selection is feasible, allowing more refined FM catalogues that avoid these issues and provide data weights for the STI routines. We present the application of angular classification with expectation-maximization (ACE) as a tool for data selection. ACE identifies clusters of FM without a priori information. The identified clusters can be used for the classification of the style-of-faulting and as weights of the FM data. We demonstrate that ACE effectively selects data that can be associated with a single stress tensor. Two application examples are given for weighted STI from South America. We use the resulting clusters and weights as a priori information for an STI for these regions and show that uncertainties of the stress tensor estimates are reduced significantly. KW - Inverse Theory KW - Statistical Methods KW - Seismicity KW - tectonics KW - Kinematics of crustal KW - mantle deformation Y1 - 2018 U6 - https://doi.org/10.1093/gji/ggy240 SN - 0956-540X SN - 1365-246X VL - 214 IS - 3 SP - 2250 EP - 2263 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Peña, Carlos A1 - Metzger, Sabrina A1 - Heidbach, Oliver A1 - Bedford, Jonathan A1 - Bookhagen, Bodo A1 - Moreno, Marcos A1 - Oncken, Onno A1 - Cotton, Fabrice T1 - Role of poroelasticity during the early postseismic deformation of the 2010 Maule megathrust earthquake JF - Geophysical research letters N2 - Megathrust earthquakes impose changes of differential stress and pore pressure in the lithosphere-asthenosphere system that are transiently relaxed during the postseismic period primarily due to afterslip, viscoelastic and poroelastic processes. Especially during the early postseismic phase, however, the relative contribution of these processes to the observed surface deformation is unclear. To investigate this, we use geodetic data collected in the first 48 days following the 2010 Maule earthquake and a poro-viscoelastic forward model combined with an afterslip inversion. This model approach fits the geodetic data 14% better than a pure elastic model. Particularly near the region of maximum coseismic slip, the predicted surface poroelastic uplift pattern explains well the observations. If poroelasticity is neglected, the spatial afterslip distribution is locally altered by up to +/- 40%. Moreover, we find that shallow crustal aftershocks mostly occur in regions of increased postseismic pore-pressure changes, indicating that both processes might be mechanically coupled. KW - Chilean subduction zone KW - poroelasticity KW - power-law rheology KW - afterslip inversion KW - InSAR KW - GNSS Y1 - 2022 U6 - https://doi.org/10.1029/2022GL098144 SN - 0094-8276 SN - 1944-8007 VL - 49 IS - 9 PB - Wiley CY - Hoboken, NJ ER - TY - JOUR A1 - Ziebarth, Malte J. A1 - von Specht, Sebastian A1 - Heidbach, Oliver A1 - Cotton, Fabrice A1 - Anderson, John G. T1 - Applying conservation of energy to estimate earthquake frequencies from strain rates and stresses JF - Journal of geophysical research : Solid earth N2 - Estimating earthquake occurrence rates from the accumulation rate of seismic moment is an established tool of seismic hazard analysis. We propose an alternative, fault-agnostic approach based on the conservation of energy: the Energy-Conserving Seismicity Framework (ENCOS). Working in energy space has the advantage that the radiated energy is a better predictor of the damage potential of earthquake waves than the seismic moment release. In a region, ENCOS balances the stationary power available to cause earthquakes with the long-term seismic energy release represented by the energy-frequency distribution's first moment. Accumulation and release are connected through the average seismic efficiency, by which we mean the fraction of released energy that is converted into seismic waves. Besides measuring earthquakes in energy, ENCOS differs from moment balance essentially in that the energy accumulation rate depends on the total stress in addition to the strain rate tensor. To validate ENCOS, we exemplarily model the energy-frequency distribution around Southern California. We estimate the energy accumulation rate due to tectonic loading assuming poroelasticity and hydrostasis. Using data from the World Stress Map and assuming the frictional limit to estimate the stress tensor, we obtain a power of 0.8 GW. The uncertainty range, 0.3-2.0GW, originates mainly from the thickness of the seismogenic crust, the friction coefficient on preexisting faults, and models of Global Positioning System (GPS) derived strain rates. Based on a Gutenberg-Richter magnitude-frequency distribution, this power can be distributed over a range of energies consistent with historical earthquake rates and reasonable bounds on the seismic efficiency. Y1 - 2020 U6 - https://doi.org/10.1029/2020JB020186 SN - 2169-9313 SN - 2169-9356 VL - 125 IS - 8 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Durand, Virginie A1 - Bentz, Stephan A1 - Kwiatek, Grzegorz A1 - Dresen, Georg A1 - Wollin, Christopher A1 - Heidbach, Oliver A1 - Martinez-Garzon, Patricia A1 - Cotton, Fabrice A1 - Nurlu, Murat A1 - Bohnhoff, Marco T1 - A two-scale preparation phase preceded an M-w 5.8 earthquake in the sea of marmara offshore Istanbul, Turkey JF - Seismological research letters N2 - We analyze the spatiotemporal evolution of seismicity during a sequence of moderate (an M-w 4.7 foreshock and M-w 5.8 mainshock) earthquakes occurring in September 2019 at the transition between a creeping and a locked segment of the North Anatolian fault in the central Sea of Marmara, northwest Turkey. To investigate in detail the seismicity evolution, we apply a matched-filter technique to continuous waveforms, thus reducing the magnitude threshold for detection. Sequences of foreshocks preceding the two largest events are clearly seen, exhibiting two different behaviors: a long-term activation of the seismicity along the entire fault segment and a short-term concentration around the epicenters of the large events. We suggest a two-scale preparation phase, with aseismic slip preparing the mainshock final rupture a few days before, and a cascade mechanism leading to the nucleation of the mainshock. Thus, our study shows a combination of seismic and aseismic slip during the foreshock sequence changing the strength of the fault, bringing it closer to failure. Y1 - 2020 U6 - https://doi.org/10.1785/0220200110 SN - 0895-0695 SN - 1938-2057 VL - 91 IS - 6 SP - 3139 EP - 3147 CY - Boulder ER - TY - JOUR A1 - Ziegler, Moritz O. A1 - Reiter, Karsten A1 - Heidbach, Oliver A1 - Zang, Arno A1 - Kwiatek, Grzegorz A1 - Stromeyer, Dietrich A1 - Dahm, Torsten A1 - Dresen, Georg A1 - Hofmann, Gerhard T1 - Mining-Induced Stress Transfer and Its Relation to a 1.9 Seismic Event in an Ultra-deep South African Gold Mine JF - Pure and applied geophysics N2 - On 27 December 2007, a 1.9 seismic event occurred within a dyke in the deep-level Mponeng Gold Mine, South Africa. From the seismological network of the mine and the one from the Japanese-German Underground Acoustic Emission Research in South Africa (JAGUARS) group, the hypocentral depth (3,509 m), focal mechanism and aftershock location were estimated. Since no mining activity took place in the days before the event, dynamic triggering due to blasting can be ruled out as the cause. To investigate the hypothesis that stress transfer, due to excavation of the gold reef, induced the event, we set up a small-scale high-resolution three-dimensional (3D) geomechanical numerical model. The model consisted of the four different rock units present in the mine: quartzite (footwall), hard lava (hanging wall), conglomerate (gold reef) and diorite (dykes). The numerical solution was computed using a finite-element method with a discretised mesh of approximately elements. The initial stress state of the model is in agreement with in situ data from a neighbouring mine, and the step-wise excavation was simulated by mass removal from the gold reef. The resulting 3D stress tensor and its changes due to mining were analysed based on the Coulomb failure stress changes on the fault plane of the event. The results show that the seismic event was induced regardless of how the Coulomb failure stress changes were calculated and of the uncertainties in the fault plane solution. We also used the model to assess the seismic hazard due to the excavation towards the dyke. The resulting curve of stress changes shows a significant increase in the last in front of the dyke, indicating that small changes in the mining progress towards the dyke have a substantial impact on the stress transfer. KW - Induced seismicity KW - static stress change KW - deep-level mining KW - tabular mining KW - Coulomb failure stress KW - 3D geomechanical numerical model Y1 - 2015 U6 - https://doi.org/10.1007/s00024-015-1033-x SN - 0033-4553 SN - 1420-9136 VL - 172 IS - 10 SP - 2557 EP - 2570 PB - Springer CY - Basel ER -