2020年4月1日四川石渠5.6级地震总结

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。

Summary of Shiqu MS 5.6 earthquake in Sichuan on April 1, 2020

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:① Seismicity 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;② Geophysical observations:there are 8 geophysical anomalies, of which 5 are deformation anomalies and 3 are electromagnetic anomalies;③ The 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.