漾濞县M_(S)6.4、玛多县M_(S)7.4地震前地电场变化分析

Geoelectric field changes before the Yangbi M_(S)6.4 and Maduo M_(S)7.4 earthquakes

2021年5月21日云南漾濞县发生M_(S)6.4地震、5月22日青海玛多县发生M_(S)7.4地震,分别分析漾濞震中500 km内12个地电场台数据、玛多震中500 km内8个地电场台数据,获知:(1)漾濞地震周围罗茨等8台优势方位角在震前出现了异常变化,弥渡等4台看不出明显异常变化;盐源等7台相关系数在震前2~6个月出现了大幅度下降,元谋\,苴林等5台相关系数看不出明显异常变化。(2)玛多地震周围门源等4台方位角在震前出现了异常变化,都兰等4台方位角看不出明显异常变化;门源等5台在玛多地震前2~6个月相关系数出现了大幅下降、变化范围明显变窄等现象,都兰、白水河、金银滩等3台优势方位角和相关系数都看不出明显异常变化。(3)两次地震分析中地电场优势方位角和相关系数异常变化在时间上皆具有同步或准同步性。

An M_(S)6.4 earthquake occurred in Yangbi County,Yunnan Province on May 21,2021,and an M_(S)7.4 earthquake occurred in Maduo County,Qinghai Province on May 22,2021.The data from twelve geoelectric stations within 500 km of Yangbi epicenter and 8 geoelectric stations within 500 km of Maduo epicenter were analyzed,respectively.The results showed that:(1)The dominant azimuth angles of eight stations around the epicenter of Yangbi earthquake showed abnormal changes before the earthquake,while those of other four stations showed no obvious anomalies;The correlation coefficients of seven stations decreased significantly in 2-6 months before the earthquake,while those of other five stations showed no obvious abnormal change.(2)The dominant azimuth angles of four stations around the epicenter of Maduo earthquake showed abnormal changes before the earthquake,while those of other four stations did not change obviously;The correlation coefficients of five stations decreased significantly and the variation range was obviously narrowed in 2-6 months before the earthquake,and those of other three stations did not show obvious abnormal changes.(3)The anomalous changes of dominant azimuth and correlation coefficient of geoelectric field during the two earthquakes are synchronous or quasi synchronous in time.