2011年日本9.0级地震前后应力场变化

通过对2011年日本9.0级地震前后不同时段震源机制解进行分析，利用FMSI震源机制反演法求解，得到此次地震前后内陆地区的应力场。研究发现，此次地震发生前，应力场比较均衡稳定，挤压应力接近水平向，而拉张应力比较复杂，方向不确定，表明该地区的地震以逆断层和走滑为主。地震发生后，日本东北地区东南部应力场变得不太稳定，该地区地震以正断层为主，最小挤压应力由垂向转变为水平向。此研究结果可以用来分析该地区地震地质背景和断层形成条件，对地球动力环境研究具有一定参考意义。

The change of stress field before and after Japan M 9 earthquake in 2011

Based on the analysis of focal mechanism in different periods before and after Japan M 9 earthquake in 2011, the stress field in the inland area before and after Japan M 9 earthquake was obtained by using the FMSI focal mechanism inversion method. Before the earthquake, the stress field is relatively stable and the compressive stress is near the horizontal level. The tensile stress is more complex and the direction is uncertain, indicating that the earthquakes in the area are mainly reverse fault and strike slip. After the earthquake, the stress field in the southeastern part of northeast Japan changed and became unstable. The normal fault is the main cause of the earthquake, and the minimum extrusion stress has changed from vertical to horizontal. The results of the study can be used to analyze the seismic geological background and fault formation conditions in this area, and have some reference and significance for the study of the earth's dynamic environment.