S wave splitting in the aftershock region of the 1995 Hyogo‐ken Nanbu earthquake
S wave splitting in the aftershock region of the 1995 Hyogo‐ken Nanbu earthquake
复制标题
1995年兵库县南部地震余震区的S波分裂
DOI：
10.1029/1998jb900024
复制
发表时间：
1999
影响因子：
--
通讯作者：
Y. Umeda
中科院分区：
文献类型：
--
作者：
K. Tadokoro;M. Ando;Y. Umeda
1995年兵库县南部地震（科比地震; M7.2）发生于1995年1月17日。1995年10月至1996年1月，由高校地震预报地球物理研究小组进行了一次余震临时观测。在余震区及其周围部署了密集的地震台网，一些地震台站直接设置在活动断层痕迹上。本文分析了兵库县南部地震余震区及其周围的S波分裂。我们检测到的空间变化的S波分裂，这可能与裂纹的方向在一个地区发生了大地震。在距离兵库县南部地震断裂带1 km以上的台站，横波偏振方向（LSPD）与区域最大水平压应力（E-W）轴平行，表明该地区存在区域构造应力引起的破裂。而在距地震断裂带500 m以内的台站，LSPD与断层走向（N45° ~ 50 ° E）平行。这表明兵库县南部地震的剪切断层作用产生了新的平行于断层的破裂，并导致S波沿地震断裂带沿着分裂。然而，在1596年断裂的活动断层上的台站，剪切断层起源各向异性并不明显。这意味着愈合过程已经关闭了1596年剪切断层产生的裂缝。因此，我们可以预期S波分裂可以成为一个有用的工具，监测活动断层愈合过程。
The 1995 Hyogo-ken Nanbu earthquake (Kobe earthquake; M7.2) occurred on January 17, 1995. A temporary aftershock observation was carried out by the Geophysical Research Group Organized by Universities for Prediction Seismology in 1995 from October 1995 to January 1996. A dense seismic network was deployed in and around the aftershock region, and some seismic stations were set directly on the active fault traces. We analyze the S wave splitting in and around the aftershock region of the Hyogo-ken Nanbu earthquake. We detect a spatial variation of S wave splitting which can be related to crack orientations in an area where a large earthquake has occurred. At stations more than 1 km away from the Hyogo-ken Nanbu earthquake fault zone, the leading shear wave polarization directions (LSPD) are found to be parallel to the axis of the regional maximum horizontal compressional stress (E-W), suggesting that cracks caused by regional tectonic stress exist in the area. However, at stations within 500 m of the earthquake fault zones, the LSPDs are parallel to the fault strikes (N45°–50°E). This suggests that new fractures were produced parallel to the faults by shear faulting of the Hyogo-ken Nanbu earthquake and resulted in S wave splitting along the earthquake fault zone. Nevertheless, shear fault origin anisotropy was not evident at stations on the active faults which ruptured in 1596. This implies that healing processes have already closed the fractures produced by shear faulting in 1596. Therefore we can expect that S wave splitting can be a useful tool for monitoring healing processes of active faults.