2013年芦山MS7.0地震序列断层结构及震源区应力场特征

使用芦山地震序列2013年4月20日至5月20日一个月的地震震相数据和M_S4.0以上地震的波形数据, 通过双差定位方法得到了3398个地震的精定位结果, 利用时间域全波形反演方法得到17个地震的矩张量解。 综合分析地震双差定位结果和芦山地震序列中强地震震源机制解, 发现芦山地震发震构造由主震断层和次级反冲断层组成, 主震断层为一走向北东、 倾向北西、 倾角约为45°的高角度逆冲断层, 次级反冲断层与主震断层走向相同, 倾向相反, 两条断层均未出露地表。 主震和余震震源机制解均为逆冲型, 几乎没有走滑分量。 震源区主压应力方位为北西向, 与发震断层走向近乎垂直。

Fault Structure and Stress field Characteristics in the Source Area of the 2013 Lushan MS7.0 Earthquake Sequence

Using seismic phase data and waveform data of M_S≥4.0 earthquakes among Lushan earthquake sequence from April 20 to May 20, 2013, we obtained precise locations of 3398 earthquakes by using double-difference earthquake location algorithm, and the moment tensor solutions of 17 earthquakes by utilizing the time-domain full waveform inversion method. Based on a comprehensive analysis of the double-difference relocation and focal mechanism solutions of middle to strong earthquakes in the Lushan earthquake sequence, we find that the seismogenic structure of the Lushan earthquake consists of a main shock fault and a secondary thrust fault. The main shock fault is a high-angle thrust fault striking NE, trending NW, and dipping approximately 45 degrees. The secondary thrust fault is the same direction with the main shock in strike, and opposite in trend. And the two faults are not exposed to the surface. Both the main shock and aftershock focal mechanism solutions are thrust-type, with almost no slip component. The direction of principal stress in the source area is NW, which is perpendicular to the seismogenic fault.