Changes in seismic activity following the 2011 Tohoku-oki earthquake: Effects of pore fluid pressure
Changes in seismic activity following the 2011 Tohoku-oki earthquake: Effects of pore fluid pressure
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2011 年东北冲地震后地震活动的变化：孔隙流体压力的影响
DOI：
10.1016/j.epsl.2013.01.017
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发表时间：
2013
影响因子：
5.3
通讯作者：
T.
中科院分区：
文献类型：
--
作者：
Terakawa;T.
通过基于库仑破裂准则的余震分析，我们研究了2011年东北(东北)地震后，孔隙流体压力对地震活动性变化的影响。日本东北部的背景构造应力场总体上以东西向挤压为特征。东北地震发生后，由于库仑破裂函数(=剪应力−=0.4×法向压应力)的减小，日本东北部上地壳的地震活动减少，但在一些限制区域，我们观察到许多震源机制对背景应力场不利的余震。通过在三维莫尔图上逐区绘制余震震源机制图，确认余震发生在一些地区的最佳取向断裂上，而另一些地区的余震发生在错向断裂上。最佳取向断裂上的余震表明，深层超压流体的流动导致了区域环境流体压力的增加。另一方面，错向断层上的余震不能归因于同震应力旋转，表明断层围压相对于环境流体压力有所增加。
We examined the effects of pore fluid pressure on seismicity changes following the 2011 off the Pacific coast of Tohoku (Tohoku-oki) earthquake through the analysis of aftershocks based on the Coulomb failure criterion. Background tectonic stress fields in Northeast Japan are generally characterized by E–W compression. After the Tohoku-oki earthquake, as expected from decrease in the Coulomb failure function (=shear stress−0.4×normal compressive stress), seismicity in the upper crust of Northeast Japan decreased except some restricted regions, where we observed many aftershocks with unfavourable focal mechanisms to the background stress fields. By mapping the focal mechanisms of aftershocks on the 3-D Mohr diagram region by region, we confirmed that the aftershocks occurred on optimally oriented faults in some regions but on misoriented faults in other regions. The aftershocks on optimally oriented faults indicate the increase in regional ambient fluid pressure caused by the flow of over-pressurized fluid from a deep reservoir. On the other hand, the aftershocks on misoriented faults, which cannot be attributed to coseismic stress rotation, indicate the increase in fault-confined fluid pressure relative to the ambient fluid pressure.