2012年6月24日宁蒗—盐源M_S5.7地震序列M_L≥3.5余震震源机制解

Focal mechanism solutions for M_L≥ 3.5 series of Ninglang-Yanyuan M_S5.7 earthquake on June 24, 2012

针对2012年6月24日宁蒗—盐源MS 5.7地震序列,基于云南地震台网及部分四川地震台网宽频带数据,采用CAP方法反演该序列主震及ML≥3.5余震的震源机制解。结果显示:主震主应力方位角为148°,俯角58°,节面Ⅰ走向:179°、倾角55°、滑动角-43°;节面Ⅱ走向:297°、倾角26°、滑动角-136°,矩心深度4 km,矩震级5.36,表现为正断层兼走滑型地震,判定节面Ⅱ为其发震断层面,永宁断裂为其发震构造。

Using broadband seismic waves of Yunnan Seismic Network and Sichuan Seismic Network as well as the CAP method, we inverted the focal mechanism solutions for ML≥ 3.5 earthquake series of Ninglang-Yanyuan MS5.7 earthquake on June 24, 2012. The result of main shock shown that, the trend and the plunge of P axis are 148°and 58°, the nodal plane Ⅰ：strike=179°, dip=55°,slip=-43°, the nodal plane Ⅱ：strike=297 °, dip=26 °,slip=-136°,respectively. Centroid depth：4 km, MW=5.36. So this is a mainly normal fault and partially strike slip type. According to the strike of the nodal plane Ⅱ consistent with the orientation of the Yongning fault, long axis of aftershocks and long axis of the isoseismic of intensity of this event, we judge the nodal plane Ⅱ is the fault plane, and the NW-trend Yongning fault is the seismogenicfault.