2020年新疆于田MS6.4地震及余震序列定位研究

LOCATION STUDY OF YUTIAN MS6.4 EARTHQUAKE AND AFTERSHOCKS SEQUENCE IN 2020

利用到时、方位角和慢度的线形化反演地震定位方法得到2020年于田MS6.4地震的参数为:35.767°N、82.581°E、深度25 km。使用双差定位方法对于田地震和M L≥2.0的98次余震事件进行了重新定位,得到结论:①于田MS6.4地震属一次单侧破裂事件,主、余震沿长轴SSW向(约25°)发展;②地震震源深度主要集中在8~18 km,地震破裂始于深部,逐渐向浅部扩展;③地震沿SSW方向长约40 km,SWW方向长约30 km;④发震构造倾向SE;⑤2008、2014和2020年的3次于田地震虽然均发生在阿尔金地震带的西南端,但空间形态不尽相同。2008年的地震余震更丰富,且序列呈近NS向条带分布;2014年地震发生在2008年地震的北东方向,整体沿NEE—SWW方向展布;此次地震在2014年地震的S向,沿SSW向发展,填补了2008年和2014年震源区中间的空区。

Using a linear inversion method for seismic location with arrival time,azimuth and slowness,the parameters of Yutian MS6.4 earthquake in 2020 are obtained as follows:35.767°N,82.581°E,and depth of 25 km.Then,double difference location method is used to relocate the Yutian earthquake and 98 aftershocks with M L≥2.0,the results show that:①Yutian MS6.4 earthquake belongs to a unilateral rupture event,and the main and aftershocks develop along the long axis SSW direction(about 25°);②the focal depth is mainly concentrated in 8~18 km,and the rupture begins at the deep part and gradually extends to the shallow part;③The earthquake is about 40 km long along the SSW direction and 30 km in the SWW direction;④the seismogenic structural tendency is SE;⑤the three Yutian earthquakes in 2008,2014 and 2020 all occurred in the southwest end of Altun seismic belt,but shares different spatial patterns.The aftershocks of earthquake in 2008 were abundant,and the sequence was near NS direction;the earthquake in 2014 occurred in the northeast direction of earthquake in 2008,and distributed along NEE-SWW direction as a whole.The earthquake in 2020 developed in S direction of earthquake in 2014,along SSW direction,filling the focal area gap between earthquake in 2008 and earthquake in 2014.