基于地磁场重复观测资料分析玛多M_(W)7.3地震前地磁场变化

Geomagnetic Field Change before and after Maduo M_(W)7.3 Earthquake Based on Repeat Geomagnetic Measurement Data

基于玛多地震周边的地磁场重复观测资料,使用泰勒多项式空间参考场方法和自然正交分量方法分别对观测资料进行日变通化和长期变化改正,获得了玛多地震前后地磁场变化特征。通过对观测和数据处理的分析,获得了各期计算结果的误差,并基于误差对地磁场变化进行了部分修正。结果表明,玛多地震1~2年岩石圈磁场年变化会出现明显的趋势转折,变化量为5~10nT。根据速度—状态依赖的摩擦定律的地震周期分析发现,震前断层滑动量较小,因此岩石圈磁场年变化并非由地震前断层滑动引起的应力扰动产生。玛多地震前地下流体的变化产生的电磁效应更可能是产生岩石圈磁场变化的原因。

In this paper,repeat geomagnetic measurement data in the surrounding areas of Maduo M_(W)7.3 earthquake from 2016 to 2021 are collected.Then,the Taylor polynomial spatial reference field method is used to correct the diurnal variation of geomagnetic,while the natural orthogonal component method is used to correct the secular variation of the geomagnetic field.In this way,the characteristics of geomagnetic field before and after Maduo M_(W)7.3 earthquake are obtained.Further,errors in the results are obtained through analyzing the measurement and the data processing,and on the basis of it,the geomagnetic field changes are corrected.The results indicate that the annual variation of the lithospheric magnetic field in 1~2 years before the Maduo M_(W)7.3 earthquake shows an obvious trend turn,and the change amount is 5~10 nT.The seismic cycle analysis according to the velocity-state-dependent friction law shows that the amount of fault slip before the earthquake is small,and so the annual variation of the lithosphere geomagnetic field is not caused by the stress disturbance related to the pre-seismic fault slip.The electromagnetic effect related to the changes in underground fluid before the Maduo M_(W)7.3 earthquake is more likely to be responsible for changes of the lithosphere geomagnetic field.