Estimation of the stress field in the region of the 2000 Western Tottori Earthquake: Using numerous aftershock focal mechanisms
Estimation of the stress field in the region of the 2000 Western Tottori Earthquake: Using numerous aftershock focal mechanisms
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DOI：
10.1029/2005jb004250
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发表时间：
2007-09
影响因子：
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通讯作者：
Y. Yukutake;Y. Iio;H. Katao;T. Shibutani
中科院分区：
文献类型：
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作者：
Y. Yukutake;Y. Iio;H. Katao;T. Shibutani
[1]我们估计了2000年鸟取县西部地震（Mw = 6.6）前后的区域应力场从众多的震源机制。为了约束主震前的应力场，我们比较了主震和主震后应力场的静态应力变化的空间分布。在余震区的北方和中部，推测主震前的偏应力值过大，不受静应力变化的影响。主震前最大主应力轴方向与构造应力场一致。另一方面，在余震区的南部，主震滑动较大的区域及其附近，由于静应力变化幅度较大，主震后应力场在空间上是不均匀的。在断层南缘附近，静应力变化的空间分布与余震P轴方位的分布一致，推测主震前的偏应力大小很小，足以受静应力变化的影响（5 MPa）。南部边缘的余震断层面的强度可能异常微弱。结果表明，主震前的应力场在小于主震断层长度的尺度上是不均匀的。
[1] We estimated the regional stress field before and after the 2000 Western Tottori Earthquake (Mw = 6.6) from numerous focal mechanisms. To constrain the stress field prior to the main shock, we compared the spatial distribution of the static stress changes generated by the main shock with the stress field following the main shock. In the northern and central parts of the aftershock region, it is inferred that the deviatoric stress magnitude prior to the main shock was too large to be affected by the static stress changes. The direction of the maximum principal stress axis prior to the main shock is consistent with the tectonic stress field. On the other hand, in the southern part of the aftershock area, in and around the region where the main shock slip was large, it is found that the stress field is spatially heterogeneous after the main shock because of the large magnitude of the static stress changes. Around the southern edge of the fault, the spatial distribution of the static stress changes is consistent with that of the P axis azimuths of the aftershocks, and it is inferred that the deviatoric stress magnitude prior to the main shock was small enough to be affected by the static stress changes (5 MPa). The strength of the preexisting aftershock fault planes in the southern edge might be exceptionally weak. It is found that the stress field prior to the main shock was inhomogeneous on scales smaller than the length of the main shock fault.