Crustal extensional faulting triggered by the 2010 Chilean earthquake: The Pichilemu Seismic Sequence
Crustal extensional faulting triggered by the 2010 Chilean earthquake: The Pichilemu Seismic Sequence
复制标题
DOI：
10.1029/2011tc002888
复制
发表时间：
2011-11-15
期刊：
影响因子：
4.2
通讯作者：
Pardo, Mario
中科院分区：
文献类型：
--
作者：
Farias, Marcelo;Comte, Diana;Pardo, Mario
我们报告了一系列地壳地震，这些地震是在 2010 年 2 月 27 日影响智利中部边缘的 M-w = 8.8 逆冲俯冲马乌莱地震之后开始的。这一活动持续了几个月，最重要的事件发生在 2010 年 3 月 11 日（M-w = 6.9 和 M-w = 7.0），震源机制正常。地震活动显示出沿着北西走向和西南倾斜的正断层从地表向下延伸至板间接触面的破裂。地震活动与该地区类似定向的新构造伸展结构相关，自上新世晚期以来，新构造伸展结构一直与北北东-南南西向逆断层共存，尽管两者自古生代以来都有较古老的活动期。这种地壳破裂可能是由马乌莱地震产生的高库仑应力变化引发的，而弧前地壳薄弱区可能存在流体，这一变化也增强了这一变化，这一点可以通过高 Vp/Vs 比来证明。相关新构造活动的发生与短期变形相一致，表明与该地区的长期构造特征有关，这些特征在震间期充当屏障，增加应变积累并引发地壳收缩断层，并在大俯冲断裂期间产生高滑移斑块，有利于引发地壳伸展断层。披市勒亩的地壳断层活动表明，尽管在马乌莱地震之前没有历史地壳地震活动，但在地震危险性分析中应考虑此类事件。
We report a sequence of crustal quakes that began after the M-w = 8.8 thrust-subduction Maule earthquake that affected the Central Chile margin on 27 February 2010. This activity lasted by several months, having the most important events on 11 March 2010 (M-w = 6.9 and M-w = 7.0) with normal focal mechanisms. Seismicity shows a rupture oriented along a NW-striking and SW-dipping normal fault from the surface down to the interplate contact. Seismicity can be correlated with neotectonics extensional structures similarly oriented in the region, which have coexisted with NNE-SSW reverse faults since the late Pliocene, even though both have older periods of activity since the Paleozoic. This crustal rupture would have been triggered by the high Coulomb stress change produced by the Maule earthquake, enhanced by likely fluid presence along weakened zones of the forearc crust as evidenced by high Vp/Vs ratio. The occurrence of relevant neotectonic activity in coincidence with short-term deformation suggests a relationship with long-term tectonic features of this region, which would have been acting as a barrier during the interseismic period, increasing the strain accumulation and triggering contractional faulting in the crust, as well as producing high slip patches during great subduction ruptures favoring triggering of crustal extensional faulting. Crustal faulting in Pichilemu suggests that this kind of events should be considered in seismic hazard analysis despite the absence of historical crustal seismic activity before the Maule earthquake.