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 - Melnick, Daniel A1 - Moreno, Marcos A1 - Quinteros, Javier A1 - Carlos Baez, Juan A1 - Deng, Zhiguo A1 - Li, Shaoyang A1 - Oncken, Onno T1 - The super-interseismic phase of the megathrust earthquake cycle in Chile JF - Geophysical research letters N2 - Along a subduction zone, great megathrust earthquakes recur either after long seismic gaps lasting several decades to centuries or over much shorter periods lasting hours to a few years when cascading successions of earthquakes rupture nearby segments of the fault. We analyze a decade of continuous Global Positioning System observations along the South American continent to estimate changes in deformation rates between the 2010 Maule (M8.8) and 2015 Illapel (M8.3) Chilean earthquakes. We find that surface velocities increased after the 2010 earthquake, in response to continental-scale viscoelastic mantle relaxation and to regional-scale increased degree of interplate locking. We propose that increased locking occurs transiently during a super-interseismic phase in segments adjacent to a megathrust rupture, responding to bending of both plates caused by coseismic slip and subsequent afterslip. Enhanced strain rates during a super-interseismic phase may therefore bring a megathrust segment closer to failure and possibly triggered the 2015 event. KW - megathrust KW - earthquake KW - cycle KW - Chile Y1 - 2017 U6 - https://doi.org/10.1002/2016GL071845 SN - 0094-8276 SN - 1944-8007 VL - 44 IS - 2 SP - 784 EP - 791 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Li, Shaoyang A1 - Moreno, Marcos A1 - Rosenau, Matthias A1 - Melnick, Daniel A1 - Oncken, Onno T1 - Splay fault triggering by great subduction earthquakes inferred from finite element models JF - Geophysical research letters N2 - We have investigated the influence that megathrust earthquake slip has on the activation of splay faults using a 2-D finite element method (FEM), taking into account the effects of gravity and variations in the frictional strength properties of splay faults. We simulated both landward-dipping and seaward-dipping splay fault geometries, and imposed depth-variable slip distributions of subduction events. Our results indicate that the two types of splay fault exhibit a similar behavior, with variations in frictional properties along the faults affecting only the seismic magnitude. The triggering process is controlled by a critical depth. Megathrust slip concentrated at depths shallower than the critical depth will favor normal displacement, while megathrust slip concentrated at depths deeper than the critical depth is likely to result in reverse motion. Our results thus provide a useful tool for predicting the activation of secondary faults and may have direct implications for tsunami hazard research. KW - earthquake deformation KW - subduction zone earthquakes KW - splay faults KW - faulting behavior KW - FEM models KW - tsunami hazards Y1 - 2014 U6 - https://doi.org/10.1002/2013GL058598 SN - 0094-8276 SN - 1944-8007 VL - 41 IS - 2 SP - 385 EP - 391 PB - American Geophysical Union CY - Washington ER -