2022年四川马尔康6.0级震群序列震源机制特征分析

The Characteristics of the Focal Mechanisms of the Ma erkang M S6.0 Earthquake Sequence in 2022

采用近震全波形矩张量方法反演了2022年四川马尔康6.0级震群序列22次地震的震源机制解,结果显示:这22次地震全部为走滑型,断层面走向呈NNW和NE两个优势方向,断层面倾角近似直立,滑动角分布在0°和180°附近,P轴优势方位为NWW-SEE向,倾伏角接近水平,表明此次地震事件主要受区域NWW-SEE向水平挤压应力场控制。3次5级以上地震震源机制均与序列其他地震的总体震源机制差异较小,说明序列震源机制较为一致。结合精定位结果综合分析认为:马尔康震群属于多断层面触发性震群,3次5级以上地震是不同断裂的破裂事件,其中5.8级和6.0级地震发震断层面走向为NNW,为左旋走滑破裂事件;5.2级地震发震断层面走向为NE,为右旋走滑破裂事件,3个发震断层均以走滑错动为主,断层面近似直立。

In this paper,the focal mechanism solutions of 22 events of the Ma erkang M S6.0 earthquake sequence were obtained with the method of full-waveform moment tensor inversion.The results show that these 22 earthquakes are strike-slip ones,and the trend of their fault plane is mainly in NNW direction and NE direction.The dip angle of the fault plane is approximately vertical,and the slip angle is close to 0°or 180°.The azimuth of the P-axis is in NWW-SEE direction,and the plunge angle is close to horizontal.This indicates that the activity of the Ma erkang M S6.0 earthquake sequence is mainly compressed in NWW-SEE direction by the regional horizontal stress field.The focal mechanisms of the three M S≥5.0 earthquakes are slightly different from the focal mechanisms of other earthquakes in the sequence.According to the results of precise location,we believe that the Ma erkang M S6.0 earthquake sequence is triggered by multiple planes.The three M S≥5.0 earthquakes were caused by different faults.The strike of the fault planes of the M S5.8 and the M S6.0 earthquake are in NNW direction;the rupture of the planes is right-lateral and strike-slip.The strike of the fault plane of the M S5.2 earthquake is in NE direction;its rupture is left-lateral and strike-slip.The fault planes of the three earthquakes are approximately vertical.