摘要
以2020年6月26日于田M_(S)6.4地震为例,采用地磁谐波振幅比法,选用距震中370km和360km范围内的且末台、狮泉河台所记录到的秒值连续波形数据,对震前地磁异常进行了提取和回溯性分析,发现地磁谐波振幅比反映了观测点深部电阻率变化,2020年于田M_(S)6.4地震前且末台和狮泉河台地磁谐波振幅比出现了较明显的异常现象。异常特征有:①地磁谐波振幅比Y_(ZHx)和Y_(ZHy)主要表现为“下降—转折—恢复”的形态,地震发生在下降型变化恢复之后上升阶段;②震前约2年起,且末台和狮泉河台谐波振幅比表现长短周期变化不同步或NS向与EW向变化不同步的现象;③且末台Y_(ZHx)(NS)和狮泉河台Y_(ZHy)(EW)谐波振幅比异常变化中的转折上升形态具有自较长周期向较短周期的迁移现象;④狮泉河台谐波振幅比趋势性异常起始时间早于且末台,持续时间平均2年左右,最大异常幅度达到0.04;⑤且末台Y_(ZHx)(NS)和狮泉河台Y_(ZHy)(EW)异常相比对应其他分量更为显著,这也许震中和台站所在位置有关系;⑥地震前和田大地电场(距震中约265km)岩体裂隙优势方位角(α)也显示异常变化,可见该地震前多地球物理探测参量的异常响应,呈现多地球物理量耦合,增加了异常可信度。
Taking the M_(S)6.4 Yutian earthquake on June 26,2020 as an example,the method of harmonic wave amplitude ratio is used to analyze the geomagnetic anomalies on the basis of the second-value data derived from Xinjiang Qiemo and Xizang Shiquanhe geomagnetic stations,370 km and 360 km away from the epicenter.The results show that before the June 26,2020 M_(S)6.4 earthquake in Yutian of Xinjiang Uygur Autonomous Region,the harmonic wave amplitude ratio of Qiemo and Shiquanhe geomagnetic station presents obvious abnormality.There are four anomaly characteristics:(1)The abnormal changes of the harmonic wave amplitude ratio Y_(ZHx) in the north-south and Y_(ZHy) in the east-west show the characteristics the form of"down-turning-recovery",and the earthquake occurred at the recovery stage.(2)About 2 years before the earthquake,the harmonic amplitude ratio of Qiemo and Shiquanhe station showed a phenomenon that the long and short period changes were not synchronized,or the NS and EW directions were not synchronized.(3)The turning and rising patterns in the abnormal change of the harmonic amplitude ratio of Qiemo station Y_(ZHx)(NS)and Shiquanhe station Y_(ZHy)(EW)have a migration phenomenon from a longer period to a shorter period.(4)The harmonic amplitude of Shiquanhe station is earlier than that of the trend anomaly at the start time of the Qimo station,with an average duration of about 2 years,and the maximum anomaly amplitude reaches 0.04.(5)The anomalies of the Shiquanhe station Y_(ZHx)(NS)and Shiquanhe station Y_(ZHy)(EW)are more significant than the corresponding other components,which may be related to the location of the epicenter and the station.(6)The pre-earthquake Hetian field(about 265 km from the epicenter)also showed abnormal changes in the dominant azimuth(α)of rock mass fractures.It can be seen that the anomalous response of multiple geophysical detection parameters before the earthquake showed the coupling of multiple geophysical variables,which increased the anomalies reliability.
作者
艾萨·伊斯马伊力
冯志生
陈界宏
宋春燕
毛志强
赵家庆
AISA Yisimayili;FENG Zhi-sheng;CHEN Jie-hong;SONG Chun-yan;MAO Zhi-qiang;ZHAO Jia-qing(Earthquake Agency of Xinjiang Uygur Autonomous Region,Urumqi 830011,China;Earthquake Agency of Jiangsu Province,Nanjing 210014,China;China University of Goscience,Hubei W uhan 430074,China)
出处
《地震》
CSCD
北大核心
2021年第2期190-202,共13页
Earthquake
基金
新疆地震科学基金(202001)
中国地震局震情跟踪青年项目(2019010409,2020010422)
中国地震局监测、预报、科研三结合项目(3JH-201901097)。
