2020年5月18日云南巧家MS 5.0地震总结

系统总结2020年5月18日云南巧家M_S 5.0地震发生前出现的地震活动和地球物理观测异常，其中：①地震活动异常：震前存在震群活动、Benioff应变比和地震发生率异常等中短期异常；②地球物理观测异常：震中200 km范围内分布重力、地磁、水位、水温、断层氢等测项，其中异常测项15项，大部分为趋势异常，异常台项比较低（5%），短临异常不突出，巧家电磁波为地震的短期异常；③综合方法：多参数概率谱计算结果在震前出现异常。对巧家M_S 5.0地震序列进行跟踪研究，发现：主震与最大余震的震级差为1.6（M_L震级），主震释放能量占序列总能量的99.64%，属主余型地震序列；主震震源机制显示为走滑型，根据余震分布，认为发震断层位于莲峰断裂和昭通-鲁甸断裂之间的NS向次级断裂。综合分析认为，在巧家M_S 5.0地震发生前，地震活动具有背景异常逐渐向中短期转变的过程，地球物理观测异常以趋势异常为主，短期异常不突出。

About Qiaojia MS 5.0 earthquake in Yunnan on May 18, 2020

The observed seismicity and geophysical anomalies before the Qiaojia M_S 5.0 earthquake in Yunnan on May 18, 2020, were systematically summarized. In terms of seismicity, some medium-term and short-term anomalies such as earthquake swarm, Benioff strain ratio, and earthquake occurrence rate emerged before the Qiaojia M_S 5.0 earthquake. In terms of geophysical observations, measurements such as gravity, geomagnetism, water level, water temperature, fault hydrogen, and so on were available within 200 km of the epicenter of the Qiaojia earthquake, and most of the 15 measurements which show abnormal before the mainshock was long-term anomalies, the anomaly ratio was relatively low (5%), and short-term information is not obvious before the Qiaojia earthquake. Qiaojia electromagnetic wave as a short-term anomaly could be explained to this earthquake. The anomaly was identified by the earthquake corresponding probability spectrum of multi-parameter of the comprehensive method before the Qiaojia earthquake. The dynamic tracking process of the Qiaojia M_S 5.0 earthquake sequence was analyzed and summarized. The magnitude difference between the mainshock and the largest aftershock was 1.6 (M_L), and the energy released by the mainshock accounts for 99.64% in the whole sequence, therefore, the earthquake sequence of the Qiaojia M_S 5.0 earthquake was a mainshock-aftershock type. The focal mechanism for the mainshock was the strike-slip type. The seismogenic fault was located on the NS trending secondary fault between the Lianfeng fault and Zhaotong-Ludian fault. In summary, the process of seismic anomalies was changing gradually from long-term to short-term. Geophysical anomalies are mainly trending type and short term anomalies did not appear or were not founded before the Qiaojia M_S 5.0 earthquake.