Abstract After large earthquakes at subduction zones, the plate interface continues moving due to mostly frictional afterslip or simply afterslip processes. Below approximately 60 km depth, the seismic moment release at the plate interface is quite small indicating that the shear strength is low and stable sliding is the prevailing process. This agrees with the lack of significant interseismic locking at deeper segments (>60 km) resulting from the inversion of geodetic data and thus low afterslip can be expected. However, inversion models that employ linear viscoelastic mantle rheology and an elastic crust result in significant afterslip at depths >60 km. In this paper, we present a combination of a 3D forward geomechanical model with power-law rheology that simulates postseismic relaxation with dislocation creep processes in the crust and upper mantle and an afterslip inversion. We estimate the cumulative viscoelastic relaxation and the afterslip distribution for the first six years following the 2010 Mw 8.8 Maule earthquake in Chile. The cumulative afterslip distribution is obtained from the inversion of the residual surface displacements between the observed displacements from the continuous GPS (cGPS) and the ones from the forward modelling. We investigate five simulations, four with different dislocation creep parameters for the crust, slab, and upper mantle and one with elastic properties for the crust and slab, and a linear viscoelastic upper mantle for comparison. Our preferred simulation considers a weak crust since it shows the best fit to the cumulative cGPS postseismic displacements, a good fit to the time-series, and, in particular, a good spatial correlation between afterslip and aftershock activity. In this simulation, most of the viscoelastic relaxation occurs in the continental lower crust beneath the volcanic arc due to dislocation creep processes. The resulting afterslip pattern from the inversion is reduced at depths >60 km, which correlates to the low cumulative seismic moment that is released from aftershocks at these depths. Furthermore, the cumulative afterslip moment release from this simulation corresponds to 10% of the main shock in six years, which is approximately half of the moment release that results from models with an elastic crust and linear viscosity in the upper mantle. We conclude that an integrated analysis by considering power-rheology with dislocation creep processes in the continental crust and upper mantle along with aftershock activity may be used to constrain location and magnitude postseismic relaxation processes better.

中文翻译：

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幂律流变学对 2010 年 Mw 8.8 Maule 地震后粘弹性松弛模式和后滑分布的影响

摘要 俯冲带发生大地震后，板块界面继续运动，主要是由于摩擦后滑或简单的后滑过程。在大约 60 公里深度以下，板块界面的地震矩释放非常小，表明剪切强度低，稳定滑动是主要过程。这与大地测量数据反演导致的更深段（> 60 km）缺乏显着的地震间锁定一致，因此可以预期低后滑。然而，采用线性粘弹性地幔流变学和弹性地壳的反演模型会导致深度 >60 公里的显着后滑。在本文中，我们提出了 3D 正向地质力学模型与幂律流变学的组合，该模型模拟了地壳和上地幔中具有位错蠕变过程的地震后弛豫以及后滑反演。我们估计了 2010 年智利 Mw 8.8 Maule 地震后前六年的累积粘弹性松弛和后滑分布。累积后滑分布是从连续 GPS (cGPS) 观测位移和前向建模观测位移之间的残余表面位移反演中获得的。我们研究了五种模拟，四种具有不同的地壳、板片和上地幔的位错蠕变参数，一种具有地壳和板片的弹性特性，以及用于比较的线性粘弹性上地幔。我们首选的模拟考虑了弱地壳，因为它显示了对累积 cGPS 震后位移的最佳拟合，与时间序列的良好拟合，特别是后滑和余震活动之间的良好空间相关性。在该模拟中，由于位错蠕变过程，大部分粘弹性松弛发生在火山弧下方的大陆下地壳中。反演产生的后滑模式在深度 >60 公里处减小，这与这些深度余震释放的低累积地震矩相关。此外，该模拟的累积后滑矩释放对应于六年内主震的 10%，大约是上地幔具有弹性地壳和线性粘度的模型产生的力矩释放的一半。