有关小震震前数天震中附近岩石圈磁场Z分量异常特征

Anomalous Characteristics of Z Component of the Lithospheric Magnetic Field near the Epicenter A Few Days before Small Earthquakes

为利用震例周边流动地磁矢量监测数据获取时间距发震较短的优势捕捉有效震磁异常信息,在河北任丘M_(S)3.2及内蒙古和林格尔M_(S)3.0地震后,对2019年4月至2020年4月和2020年4—9月两期岩石圈磁场变化模型进行计算发现:震中附近Z分量相对异常特征较为明显,出现一定面积正异常高值区;去除趋势性变化成分后,局部异常值约2~3 nT左右,影响范围在方圆50 km左右;且第二期任丘M_(S)3.2震中附近出现较为显著的负异常区,范围、量值和震前异常特征相当,可能和震后岩石圈磁场形态恢复有关。

In order to take advantage of the short seismogenic time to capture effective seismomagnetic anomaly information,the lithospheric magnetic field variation models from April 2019 to April 2020 and from April to September 2020 were calculated after the Renqiu M_(S)3.2 earthquake in Hebei and Helinger M_(S)3.0 earthquake in Inner Mongolia.It is found that the relative anomaly of Z component near the epicenter is more obvious,and there is a certain area of high positive anomaly.After removing the components of trend change,the local outliers were about 2~3 nT,and the influence range was about 50 km.In addition,there were significant negative anomalies near the epicenter of Renqiu M_(S)3.2 in the second stage,which were similar in scope and magnitude to those before the earthquake,and may be related to the recovery of the lithospheric magnetic field shape after the earthquake.