2014年阿拉善块体西缘两次中强地震震源机制解

2014年2月12日新疆于田发生了MS7.3地震,之后在阿拉善块体西缘相继发生了蒙古4.9级、新疆哈密5.1级地震。利用甘肃"十五"数字地震台网的波形资料,采用CAP方法反演这两次地震的震源机制解。结果显示蒙古4.9级地震为走滑型,而新疆哈密5.1级属于逆冲型,表明青藏块体与阿拉善块体之间的作用增强引发了这两次地震活动。

Focal Mechanism Solutions of Two Moderate-strong Earthquakes of 2014 in the West Alax Block

After the Yutian, Xinjiang earthquake of M_S7.3 that occurred on February 12, 2014, the Mongolia earthquake of M_S4.9 and Hami, Xinjiang earthquake of M_S5.1 occurred on the western margin of the Alax block. This shows that seismic activity is strengthening on the western margin of the Alax block. The cut-and-paste(CAP) method performs inversion of the entire profile of an earthquake, the result of which has advantages of relatively small merit that rely on the modeling of speed and lateral movement of the earth''s crust. Its basic principle is splitting seismic broadband waveform data into Pnl wave and surface-wave parts, calculating the objective error function of the observed and theoretical seismograms, performing a grid search in the assigned parameter space, and searching for the focal mechanism and focal(centroid) depth using the two global minimum variances. In this study, using wave data from the Digital Seismological Network of Gansu Province and adopting the CAP method, we determined the focal mechanisms of the two earthquakes. The result shows that the focal mechanisms of the Mongolia M_S4.9 and Hami, Xinjiang M_S5.1 earthquakes were strike-slip and thrust, respectively.Our analysis concludes that the occurrence of the Mongolia M_S4.9 and Hami, Xinjiang M_S5.1 earthquakes exhibits a correlation with the interaction of the Qinghai-Tibet block and the Alax block.