地震压磁效应计算及实例分析

doi:10.12196/j.issn.1000-3274.2022.03.004

摘要/Abstract

摘要： 为了解地震产生的地磁异常, 本文定量计算了一种地震地磁异常现象地震压磁效应。首先介绍了压磁效应定量计算的理论方法, 建立了纯走滑和纯逆冲的简单断层模型, 计算了断层滑动产生的压磁效应, 结果显示压磁效应形态具有一定的对称性, 滑动面走向对压磁效应形态影响较大, 滑动面的埋深对压磁效应量值影响较大。根据2008年汶川M_W7.9地震两个非均匀滑动模型, 计算了地震产生的压磁效应, 结果显示较大的磁场变化出现在滑动面上, 在滑动面两侧压磁效应量值衰减得很快, 在距离滑动面几十千米时, 压磁场衰减至1 nT, 甚至更小。使用成都地磁台地震前后观测数据获得了高于背景噪声水平的地磁场变化, 为+0.45 nT, 该变化与使用大地测量观测资料反演得到的滑动模型计算的压磁效应比较一致, 说明合理的压磁模型能够解释观测的同震稳定的地磁变化。

关键词: 震磁异常, 压磁效应, 定量计算, 2008年汶川M_W7.9地震

Abstract: In this paper, a seismomagnetic phenomenon due to piezomagnetic effect is numerical calculated to help understanding the magnetic anomaly associated with earthquakes. The theory of piezomagnetic effect is introduced and the piezomagnetic field resulting from strike slip fault and dip slip fault are calculated. The pattern of the piezomagnetic field is geometrical symmetry for simple slip model and depends on the strike direction of the fault. The total intensity of the geomagnetic field changes is influenced by the burial depth of slip. According to the piezomagnetic field resulting from two slip models of the 2008 Wenchuan M_W7.9 earthquake, larger magnetic field changes occur on slip plane and decays quickly with the distance to epicenter in the bilateral of slip plane. The piezomagnetic field is reduced to about 1 nT or less in area which locates tens kilometres away from epicenter. Based on the observed data of Chengdu geomagnetic observatory before and after the earthquake, a geomagnetic field change of 0.45 nT which is above the background noise level is obtained. The piezomagnetic effect calculated from slip model according to the inversion of geodetic surveying data is consistent with observed data which infers that suitable piezomagnetic model can explain static coseismic geomagnetic changes.

Key words: Seismomagnetic anomaly, Piezomagnetic effect, Numerical calculation, the 2008 Wenchuan M_W7.9 earthquake

中图分类号:

P315.7

宋成科. 地震压磁效应计算及实例分析[J]. 地震, 2022, 42(3): 52-63.

SONG Cheng-ke. Piezomagnetic Effect Calculation of Earthquakes and Case Analysis[J]. EARTHQUAKE, 2022, 42(3): 52-63.

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