Hormazábal Joaquín, Moreno Marcos, Ortega-Culaciati Francisco, Báez Juan Carlos, Peña Carlos, Sippl Christian, González-Vidal Diego, Ruiz Javier, Metzger Sabrina, Yoshioka Shoichi
Department of Geophysics, Faculty of Physical and Mathematical Sciences, University of Chile, Santiago, Chile.
Department of Structural and Geotechnical Engineering, Pontificia Universidad Católica, Santiago, Chile.
Sci Rep. 2023 Nov 9;13(1):19511. doi: 10.1038/s41598-023-45369-9.
Large subduction earthquakes induce complex postseismic deformation, primarily driven by afterslip and viscoelastic relaxation, in addition to interplate relocking processes. However, these signals are intricately intertwined, posing challenges in determining the timing and nature of relocking. Here, we use six years of continuous GNSS measurements (2015-2021) to study the spatiotemporal evolution of afterslip, seismicity and locking after the 2015 Illapel earthquake ([Formula: see text] 8.3). Afterslip is inverted from postseismic displacements corrected for nonlinear viscoelastic relaxation modeled using a power-law rheology, and the distribution of locking is obtained from the linear trend of GNSS stations. Our results show that afterslip is mainly concentrated in two zones surrounding the region of largest coseismic slip. The accumulated afterslip (corresponding to [Formula: see text] 7.8) exceeds 1.5 m, with aftershocks mainly occurring at the boundaries of the afterslip patches. Our results reveal that the region experiencing the largest coseismic slip undergoes rapid relocking, exhibiting the behavior of a persistent velocity weakening asperity, with no observed aftershocks or afterslip within this region during the observed period. The rapid relocking of this asperity may explain the almost regular recurrence time of earthquakes in this region, as similar events occurred in 1880 and 1943.
大型俯冲地震会引发复杂的震后变形，除板块间重新锁定过程外，主要由余滑和粘弹性松弛驱动。然而，这些信号错综复杂地交织在一起，给确定重新锁定的时间和性质带来了挑战。在此，我们利用六年的连续全球导航卫星系统（GNSS）测量数据（2015 - 2021年）来研究2015年伊拉佩尔地震（震级8.3）后余滑、地震活动和锁定的时空演变。余滑由经幂律流变学建模的非线性粘弹性松弛校正后的震后位移反演得到，锁定分布则从GNSS台站的线性趋势中获取。我们的结果表明，余滑主要集中在最大同震滑动区域周围的两个地带。累积余滑（相当于震级7.8）超过1.5米，余震主要发生在余滑斑块的边界。我们的结果揭示，经历最大同震滑动的区域迅速重新锁定，表现出持续速度弱化凹凸体的行为，在观测期内该区域未观测到余震或余滑。这个凹凸体的快速重新锁定可能解释了该区域地震几乎规律的复发时间，因为1880年和1943年发生过类似事件。
