山西原平M_L4.7地震矩张量反演

The Moment Tensor Inversion of Yuanping M_L4.7 Earthquake in Shanxi Province

利用山西区域地震台网数字波形资料,在对地震重新定位的基础上,对2016年4月7日山西原平M L4.7地震进行了矩张量反演计算与参数的稳定性评价,获得了此次地震的最佳双力偶解;并将反演结果与不同台站垂向分量的P波极性在震源球上的分布位置,以及利用Snoke方法和CAP方法得到的震源机制解进行对比,验证了参数的合理性与可靠性。结果显示:最佳双力偶解的节面Ⅰ参数为走向143°,倾向63°,滑动角-66°;节面Ⅱ走向278°,倾向36°,滑动角-128°;震源机制类型属于正断兼有右旋走滑分量,最佳震源深度11~14 km.主压应力P轴方位角94°,倾角64°;主张应力T轴方位角216°,倾角15°;标量地震矩M 0=2.492 64×10^15 N·m,矩震级结果为M W=4.2,与M S震级基本一致。

According to the China Earthquake Networks Center(CENC),an earthquake with M L=4.7 occurred in Yuanping,Shanxi Province on April 7,2016.It is important to determine the focal mechanism for further understanding the seismicity and generation mechanism of moderate-strong earthquakes of this region.Based on the digital seismic data recorded on the Shanxi Seismic Network and the precise location of the seismic sequence by Hypo2000 method,we investigated the best double-couple focal mechanism for this event.The seismic moment tensor was determined with uncertainty estimation.To verify the reliability of obtained parameters,the inversion results are then compared with the distribution of P wave polarity of vertical components of different stations on the source sphere,and compared with the focal mechanism solutions obtained by Snoke method and CAP method.The results show that the node surfaceⅠparameters of the best double-couple focal mechanism solution is strike 143°,dip 63°,rake-66°;nodeⅡstrike 278°,dip 36°,rake-128°.It is characterized by double couple model as a normal faulting with right-lateral strike-slip component and the optimal focal depth is 11~14 km.The azimuth and plunge of the principal compressive stress P axis are 94°and 64°,respectively.The azimuth and plunge of the principal tensile stress T axis are 216°and 15°,respectively.The scalar seismic moment is M 0=2.492 64×10^15 N·m and the moment magnitude,M W,is consistent with the surface-wave magnitude,M S.