2021—2022年川滇地区4次M_(S)≥6.0地震前井下地电阻率观测的异常变化  

APPARENT RESISTIVITY ABNORMAL CHANGES OF BOREHOLE MONITORING BEFORE FOUR M S≥6.0 EARTHQUAKES IN SICHUAN-YUNNAN AREA FROM 2021 TO 2022

作　　者：解滔[1] 韩盈 于晨 XIE Tao;HAN Ying;YU Chen(China Earthquake Networks Center,CEA,Beijing 100045,China)

机构地区：[1]中国地震台网中心,北京100045

出　　处：《地震地质》2023年第6期1370-1384,共15页Seismology and Geology

基　　金：国家自然科学基金(42104075);北京市自然科学基金(8212045)共同资助。

摘　　要：2021—2022年川滇地区先后发生了云南漾濞M_(S)6.4、四川芦山M_(S)6.1、马尔康M_(S)6.0和泸定M_(S)6.84次M_(S)≥6.0地震。距这些地震震中400km的范围内布设有红格、冕宁、甘孜井下地电阻率观测站,其观测数据在这4次地震前出现了不同程度和形态的中短期异常变化。红格站EW和NS测道自2020年12月开始出现同步下降变化,2021年漾濞M_(S)6.4地震后NS测道的异常恢复,但EW测道仍然持续下降,截至2022年9月5日泸定M_(S)6.8地震发生,EW测道的异常持续时间约为21个月。甘孜站N10°E测道的下降异常变化始于2022年4月,6月底开始出现转折回升,10月异常恢复,其间先后发生芦山M_(S)6.1、马尔康M_(S)6.0、泸定M_(S)6.8地震。2022年9—11月,甘孜站N60°W测道出现年变畸变异常,2023年1月26日泸定再次发生M_(S)5.6地震。冕宁站EW、NS、N45°W测道自2022年6月下旬开始出现同步上升变化,于泸定M_(S)6.8地震后异常恢复。依据这些异常变化,在周、月会商中对2021年漾濞M_(S)6.4、2022年泸定M_(S)6.8、2023年泸定M_(S)5.6地震做出了短期预测。There have been four M_(S)≥6.0 earthquakes,i.e.the Yangbi M_(S)6.4,Lushan M_(S)6.1,Maerkang M_(S)6.0 and Luding M_(S)6.8,occurred in Sichuan-Yunnan area from 2021 to 2022.Three borehole apparent resistivity monitoring stations of Hongge,Mianning and Garzê,normally operated within 400km away from these earthquakes.These stations recorded different types of middle-short abnormal changes before the four earthquakes.The EW and NS arrays at Hongge station began to display synchronous decline change since December 2020.According to the empirical relationship between the duration of the anomaly and the magnitude,it is predicted that there is a possibility of a magnitude 6.0 earthquake in the Sichuan-Yunnan border area.But there had been no short-term abnormal changes that can give a forecast opinion on a time scale.Short-term abnormal changes appeared at Hongge station in March 2021.The maximum decline magnitudes of the NS and EW arrays were 2.1%and 1.4%,respectively.We believed that the risk of a strong earthquake has further increased.The distance from the Yangbi earthquake to Hongge station is 232km.Data of NS array recovered to normal status after the Yangbi M_(S)6.4 earthquake in 2021,but the data of EW array continued to decline.In the fault virtual dislocation(FVD)model,the coseismic slips are loaded in a way of equal in magnitude but opposite in direction,which provides the relative deformation around the epicenter.In a compressive tectonic region,compressive areas from the FVD model can be formed as the areas with compression enhancement.The dilatant areas cannot be distinguished between absolutely dilatant areas and compressive areas.However,they can be regarded as relatively dilatant areas where the original extensive stress is enhanced,or the original compressive stress is released to some extent.It is found that Hongge station is located in the relative expansion region generated by the Yangbi earthquake.Abnormal changes at Hongge station are not only affected by the seismogenic process of the Yangbi ear

关 键 词：地电阻率 井下观测 川滇地区 地震 异常变化 

分 类 号：P315.722[天文地球—地震学]