TY - JOUR A1 - Li, Shaoyang A1 - Moreno Switt, Marcos A1 - Bedford, Jonathan A1 - Rosenau, Matthias A1 - Heidbach, Oliver A1 - Melnick, Daniel A1 - Oncken, Onno T1 - Postseismic uplift of the Andes following the 2010 Maule earthquake BT - Implications for mantle rheology JF - Geophysical research letters N2 - Postseismic surface deformation associated with great subduction earthquakes is controlled by asthenosphere rheology, frictional properties of the fault, and structural complexity. Here by modeling GPS displacements in the 6 years following the 2010 M-w 8.8 Maule earthquake in Chile, we investigate the impact of heterogeneous viscosity distribution in the South American subcontinental asthenosphere on the 3-D postseismic deformation pattern. The observed postseismic deformation is characterized by flexure of the South America plate with peak uplift in the Andean mountain range and subsidence in the hinterland. We find that, at the time scale of observation, over 2 orders of magnitude gradual increase in asthenosphere viscosity from the arc area toward the cratonic hinterland is needed to jointly explain horizontal and vertical displacements. Our findings present an efficient method to estimate spatial variations of viscosity, which clearly improves the fitting to the vertical signal of deformation. Lateral changes in asthenosphere viscosity can be correlated with the thermomechanical transition from weak subvolcanic arc mantle to strong subcratonic mantle, thus suggesting a stationary heterogeneous viscosity structure. However, we cannot rule out a transient viscosity structure (e.g., power law rheology) with the short time span of observation. Y1 - 2017 U6 - https://doi.org/10.1002/2016GL071995 SN - 0094-8276 SN - 1944-8007 VL - 44 IS - 4 SP - 1768 EP - 1776 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Ziegler, Moritz O. A1 - Heidbach, Oliver A1 - Zang, Arno A1 - Martinez-Garzon, Patricia A1 - Bohnhoff, Marco T1 - Estimation of the differential stress from the stress rotation angle in low permeable rock JF - Geophysical research letters N2 - Rotations of the principal stress axes are observed as a result of fluid injection into reservoirs. We use a generic, fully coupled 3-D thermo-hydro-mechanical model to investigate systematically the dependence of this stress rotation on different reservoir properties and injection scenarios. We find that permeability, injection rate, and initial differential stress are the key factors, while other reservoir properties only play a negligible role. In particular, we find that thermal effects do not significantly contribute to stress rotations. For reservoir types with usual differential stress and reservoir treatment the occurrence of significant stress rotations is limited to reservoirs with a permeability of less than approximately 10(-12)m(2). Higher permeability effectively prevents stress rotations to occur. Thus, according to these general findings, the observed principal stress axes rotation can be used as a proxy of the initial differential stress provided that rock permeability and fluid injection rate are known a priori. Y1 - 2017 U6 - https://doi.org/10.1002/2017GL073598 SN - 0094-8276 SN - 1944-8007 VL - 44 SP - 6761 EP - 6770 PB - American Geophysical Union CY - Washington ER -