Gradual unlocking of plate boundary controlled initiation of the 2014 Iquique earthquake
Gradual unlocking of plate boundary controlled initiation of the 2014 Iquique earthquake
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DOI：
10.1038/nature13681
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发表时间：
2014-08-21
期刊：
影响因子：
64.8
通讯作者：
Vilotte, Jean-Pierre
中科院分区：
文献类型：
--
作者：
Schurr, Bernd;Asch, Guenter;Vilotte, Jean-Pierre
2014年4月1日，智利北方发生8.1级地震。智利综合板块边界天文台监测了整个事件序列，为主事件的积累及其破裂演变提供了前所未有的分辨率。在这里，我们表明，伊基克地震打破了所谓的北方智利地震空区的中心部分，南美洲板块边界的最后一个主要部分，在过去的世纪没有破裂（1，2）。自2013年7月以来，三个地震集群，每个持续几周，袭击了板块边界的这一部分，地震的峰值震级不断增加。从第二个集群开始，大地测量观测表明，表面位移可以与板块界面上的滑动。这些地震群及其滑移瞬变占据了板块界面的一部分，该界面是完全锁定和蠕动部分之间的过渡。在这次地震之前，前震的B值在地震前几年逐渐下降，在伊基克地震前几天扭转了趋势。主震最后在前震区的北方端成核，绕过一个锁定的补丁，并主要向下倾斜向更高的锁定破裂。在前震区的下倾和锁定斑块的边缘处，滑动峰值立即达到。我们的结论是，逐渐减弱的地震空区的中央部分加重了中间地震耦合区的前震活动是有助于导致最终失败，区分伊基克地震从大多数大地震。最后，只有三分之一的差距被打破，其余的锁定部分现在构成了一个显着的，增加的地震危险与潜在的主机与震级> 8.5的地震。
On 1 April 2014, Northern Chile was struck by a magnitude 8.1 earthquake following a protracted series of foreshocks. The Integrated Plate Boundary Observatory Chile monitored the entire sequence of events, providing unprecedented resolution of the build-up to the main event and its rupture evolution. Here we show that the Iquique earthquake broke a central fraction of the so-called northern Chile seismic gap, the last major segment of the South American plate boundary that had not ruptured in the past century(1,2). Since July 2013 three seismic clusters, each lasting a few weeks, hit this part of the plate boundary with earthquakes of increasing peak magnitudes. Starting with the second cluster, geodetic observations show surface displacements that can be associated with slip on the plate interface. These seismic clusters and their slip transients occupied a part of the plate interface that was transitional between a fully locked and a creeping portion. Leading up to this earthquake, the b value of the foreshocks gradually decreased during the years before the earthquake, reversing its trend a few days before the Iquique earthquake. The mainshock finally nucleated at the northern end of the foreshock area, which skirted a locked patch, and ruptured mainly downdip towards higher locking. Peak slip was attained immediately downdip of the foreshock region and at the margin of the locked patch. We conclude that gradual weakening of the central part of the seismic gap accentuated by the foreshock activity in a zone of intermediate seismic coupling was instrumental in causing final failure, distinguishing the Iquique earthquake from most great earthquakes. Finally, only one-third of the gap was broken and the remaining locked segments nowpose a significant, increased seismic hazard with the potential to host an earthquake with a magnitude of > 8.5.