2020年4月1日四川石渠5.6级地震总结

Summary of Shiqu M_(S)5.6 earthquake in Sichuan on April 1,2020

系统梳理2020年4月1日四川石渠5.6级地震震前地震活动异常特征、地球物理观测异常以及区域构造情况,结果如下:①地震活动:石渠5.6级地震震中区域属于历史弱震区,震前出现前兆震群,也是其前震活动;②地球物理观测:出现8项异常,其中形变5项,电磁3项,且电磁异常对于该地震具有预测意义;③综合方法:地震发生前,震中附近存在W_(q)值异常。石渠5.6级地震发生在五道梁—长沙贡玛断裂带上,震源机制解显示为走滑型破裂。该序列类型为前震—主震—余震型,主震前存在明显的前震活动,余震较为丰富,序列活动呈阶段性衰减特征。综合分析认为,对于历史弱震区,可以通过分析地球物理观测异常和地震活跃时段的b值,为区域地震危险性评估提供依据,同时可利用地震序列参数h值和b值,对震后余震水平进行有效评估。

An M_(S)5.6 earthquake occurred in Shiqu County,Sichuan Province on April 1,2020.The historical seismicity,geophysical observations before the mainshock,and tectonic background are systematically summarized in this paper.The results show that:①Seismicity anomalies:the epicenter area is a weak earthquake area and there are precursory earthquake swarms before the mainshock,which are also the foreshocks of the Shiqu M_(S)5.6 earthquake;②Geophysical observations:there are 8 geophysical anomalies,of which 5 are deformation anomalies and 3 are electromagnetic anomalies;③The comprehensive method demonstrates that there is a W_(q)-value anomaly before the Shiqu M_(S)5.6 earthquake.The Shiqu M_(S)5.6 earthquake occurred on the Wudaoliang-Changshagongma fault zone,and the focal mechanism solution of the mainshock shows it is strike-slip faulting.The seismic activity of the Shiqu M_(S)5.6 earthquake sequence indicates that there is an obvious foreshock activity before the mainshock.Thus,the Shiqu M_(S)5.6 earthquake sequence is a foreshock–mainshock–aftershock sequence.Moreover,there are lots of aftershocks and the current daily cumulative rate of the sequence shows an episodic attenuation trend.The systematical analysis of the Shiqu M_(S)5.6 earthquake indicates that analyzing geophysical anomalies and b-value in seismically active periods can provide more information to effectively determine the seismic risk of a weak earthquake area.At the same time,by calculating the h-value and b-value of the earthquake sequence,the maximum aftershock magnitude can be effectively estimated.