2022年昌吉M_(S)4.8地震地下流体异常特征

UNDERGROUND FLUID ANOMALY CHARACTERISTICS OF 2022 CHANGJI M_(S)4.8 EARTHQUAKE

通过对2022年7月20日昌吉M_(S)4.8地震前地下流体异常特征和震源机制解进行分析,总结地震前地下流体异常特征和分布范围。分析表明:昌吉地震地下流体异常在80~140 km之内。从发震时间来看,昌吉地震前地下流体异常可分为短临异常和中期趋势背景异常,其中以短临异常为主。中期趋势背景异常呈现出新26泉动水位先下降后上升。短临异常表现为新04井静水位上升、新20井静水位上升、新15泉电导率上升。异常在空间上呈现出EW向分布。震源机制解结果表明:节面I走向81°,倾角69°,滑动角174°;节面II走向173°,倾角84°,滑动角21°。P轴方位305°,T轴方位为39°,表明昌吉M_(S)4.8地震是在NWW向挤压,NEE向拉伸的应力作用下发生的地震事件。昌吉地震震源机制解所得主压应力作用方向与地震前异常展布方向相同。

By analyzing the characteristics of underground fluid anomalies and focal mechanism solu-tions before Changji M_(S)4.8 earthquake on July 20,2022,the characteristics and distribution range of underground fluid anomalies before the earthquake were summarized.The analysis shows that the un-derground fluid anomaly of the Changji earthquake is within 80~140 km.From the perspective of the time from the earthquake,the underground fluid anomalies before the Changji earthquake can be divided into short-term anomalies and medium-term trend background anomalies,of which short-term anomalies are the main ones.Background anomaly of the medium-term trend shows that the dynamic water level of Xin 26 Spring decreases first and then increases.The short-term and impending anoma-lies are manifested as the rise of static water level in Xin 04 Well,the rise of static water level in Xin 20 Well and the rise of conductivity in Xin 15 Spring.The anomaly shows an EW distribution in space.The focal mechanism solution results show that the nodal plane I strikes 81°,the dip angle is 69°,and the slip angle is 174°.The nodal plane II has a strike of 173°,an inclination of 84°,and a sliding angle of 21°.The P-axis orientation is 305°,and the T-axis orientation is 39°,indicating that Changji M_(S)4.8 earthquake was an earthquake event under the stress of NWW compression and NEE extension.The direction of the main compressive stress obtained from the focal mechanism solu-tion of Changji earthquake is the same as that of anomaly distribution before the earthquake.