门源M_(S)6.9地震前地电场优势方位角与加卸载响应比异常变化分析  

Abnormal variation of dominant azimuth and load/unload response ratio of geoelectric field before the Menyuan M_(S)6.9 earthquake

作　　者：辛建村 孙君嵩 于晨 方炜[1] 赵杰 杨宜海 XIN Jiancun;SUN Junsong;YU Chen;FANG Wei;ZHAO Jie;YANG Yihai(Shaanxi Earthquake Agency, Xi'an 710068, Shaanxi, China;Jiangsu Earthquake Agency, Nanjing 210014, Jiangsu, China;China Earthquake Network Center, Beijing 100045, China)

机构地区：[1]陕西省地震局,陕西西安710068 [2]江苏省地震局,江苏南京210014 [3]中国地震台网中心,北京100045

出　　处：《地震工程学报》2022年第2期415-424,共10页China Earthquake Engineering Journal

基　　金：国家自然科学基金(42004048);陕西省自然科学基础研究计划(2020JQ-979)。

摘　　要：2022年1月8日在青海门源县发生M_(S)6.9地震,基于震中300 km范围内地电场近5年观测资料,综合分析选取9个观测站,根据大地电场岩体裂隙水(电荷)渗流(移动)模型计算其优势方位角,并尝试以地电场为响应量,通过库仑应力触发模型的加卸载响应比(LURR)计算方法,计算地电场LURR值。结果显示:(1)两种不同方法计算的地电场异常站在空间分布上具有一致性,其中古丰、黄羊川、寺滩和兰州站地电场优势方位角、LURR在震前皆出现异常变化,而山丹等其他站方位角、LURR均看不出明显的异常变化。(2)兰州和寺滩站两种计算方法的结果时序变化较为吻合,表现出准同步性。进一步结合震源机制解对异常观测站优势方位与区域主压应力P走向的关联进行分析,结果表明基本符合岩石物理学理论,这在一定程度上可增强地电场优势方位角方法在分析地震前兆异常中的可信度。地电场优势方位角以及LURR值两种计算方法在机理上具有关联性,综合分析其异常演化特征可能有助于进一步认知地震孕育的物理过程。An M_(S)6.9 earthquake occurred in Menyuan County,Qinghai Province on January 8,2022.Based on the observation data of the electric field within 300 km of the epicenter in recent 5 years,9 observation stations were analyzed and selected.According to the seepage(movement)model of rock fissure water(charge),the dominant azimuth of the geoelectric field was calculated.The loading and unloading response ratio(LURR)value of the geoelectric field was calculated through the LURR calculation method of Coulomb stress-triggered model.The results showed that:(1)The stations with geoelectric field anomalies calculated by the two different methods are consistent in spatial distribution.Among them,the dominant azimuth and LURR of the geoelectric field at Gufeng,Huangyangchuan,Sitan,and Lanzhou stations showed abnormal changes before the earthquake,while those at Shandan and other stations did not show obvious anomalies.(2)The time series changes of Lanzhou and Sitan stations using the two calculation methods are consistent,showing quasi synchronization.Combined with the focal mechanism solution,the correlation between the dominant azimuth of abnormal stations and the principal compressive stress P-axis direction was analyzed,and the results basically conform to the petrophysics theory.The two calculation methods of geoelectric field dominant azimuth and LURR value are related in mechanism,and a comprehensive analysis of their abnormal evolution characteristics may help to further understand the physical process of earthquake preparation.

关 键 词：门源M_(S)6.9地震 地电场 优势方位角 加卸载响应比 主压应力P走向 

分 类 号：P315[天文地球—地震学]