2014年盈江双震的破裂历史

2014年5月24日在云南省盈江县发生M_s5.6级地震(主震A), 于5月30日在其附近再次发生M_s6.1级地震(主震B). 我们挑选云南省地震台网记录的数字波形资料, 借助于经验格林函数技术提取了这两次地震的震源时间函数,获得了其破裂历史. 为了利用经验格林函数技术提取震源时间函数,我们首先利用优选的速度模型,采用逆时成像技术重新确定了主震A和B以及挑选的6次较大余震的震源位置,并利用双差定位技术确定了主震与余震之间的相对位置;然后利用广义极性振幅技术反演了这些事件的震源机制;最后,根据主震和余震的相对位置以及震源机制特征挑选最优台站记录,提取了两个主震的震源时间函数. 结果表明,主震A持续时间约3.5 s, 分两个阶段,第一阶段0~1.3 s, 第二阶段1.3~3.5 s;主震B持续时间约5.0 s, 其过程比A复杂,至少可以分为五个阶段,第一阶段0~0.7 s, 第二阶段0.7~1.6 s, 第三阶段1.6~2.5 s,第四阶段2.5~3.8 s,第五阶段3.8~5.0 s.

Rupture histories of the 2014 Yingjiang double earthquakes

On May 24, 2014, an M_s5.6 earthquake (mainshock A) struck Yingjiang county, Yunnan province, China, and on May 30, another M_s6.1 earthquake (mainshock B) occurred near the mainshock A. We obtained apparent source time functions (ASTFs) or rupture histories for the 2 events by the empirical Green's function technique (EGFT) from the selected digital waveform data of Yunnan Seismograph Network. In order to retrieve the ASTFs by the EGFT, at first, the locations of the mainshocks and 6 selected aftershocks were specially determined with the reversal-time imaging technique using an already selected velocity model, and the relative locations were determined with the DD-technique; then the focal mechanisms were obtained by the GPAT(Generalized Polarity and Amplitude Technique); finally, the best station and recordings were chosen after consideration of the locations and mechanisms of the mainshocks relatively to the aftershocks, and the ASTFs of the mainshocks were retrieved using the data from the chosen station. As the results showed, the mainshock A had a total duration of 3.5 s, and consisted of two obvious periods, with the first 0~1.3 s while the second 1.3~3.5 s; and the mainshock B had more complicated process than the mainshock A, with five periods recognized at least, the first 0~0.7 s, the second 0.7~1.6 s, the third 1.6~2.5 s, the fourth 2.5~3.8, and the last 3.8~5.5 s.