论文部分内容阅读
根据大量震源机制估计了2000年鸟取县西部地震(MW=6.6)前后的区域应力场。为约束主震前的应力场,我们比较了主震产生的静态应力变化与主震后应力场的空间分布。在余震区的北部和中部,推测主震前的偏应力量值太大,不会受到静态应力变化的影响。主震前的最大主应力轴的方向与构造应力场一致。而在余震区南部,主震滑动较大的地区及其周围,发现由于静态应力变化较大,主震后应力场的空间分布很不均匀。在断层南端附近,静态应力变化的空间分布与余震的P轴方位角一致,推测主震前的偏应力量值小到足以受到静态应力变化(5MPa)影响的地步。断层南端原有余震断层面的强度可能特别弱。发现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。
Based on a large number of focal mechanisms, the regional stress field before and after the western Tottori earthquake in 2000 (MW = 6.6) was estimated. In order to restrain the stress field before the main shock, we compared the static stress changes produced by the main shock with the spatial distribution of the stress field after the main shock. In the northern and central aftershocks, it is speculated that the magnitude of the pre-main-shock bias is too large to be affected by static stress changes. The direction of the maximum principal stress axis before the main shock is consistent with the tectonic stress field. In the southern part of the aftershock zone, where the mainshock slides largely and around it, it is found that the spatial distribution of the stress field after the main shock is not uniform due to the large changes in static stress. Near the southern end of the fault, the spatial distribution of static stress is consistent with the azimuth of the P-axis of aftershocks. It is presumed that the magnitude of the prestress bias is small enough to be affected by the static stress (5 MPa). The intensity of the original aftershock fault plane at the southern tip of the fault may be particularly weak. It is found that the stress field before the main shock is not uniform on the scale smaller than the length of the main fault.