Piezomagnetic Anomalies Associated with the 2021 MW 7.3 Maduo (China) Earthquake

Chengke Song,Fei Chu,Pengtao Zhang,Can Wang

doi:10.3390/app12031017

Chengke Song, Fei Chu + Show 2 more

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https://doi.org/10.3390/app12031017

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Abstract

Stress changes due to earthquake rupture can disturb geomagnetic fields significantly. In order to investigate the impact of the 2021 MW 7.3 Maduo earthquake on geomagnetic fields, a piezomagnetic model is constructed based on the coseismic slip to calculate the static coseismic piezomagnetic anomalies (PMs). The PMs are considerable in near-field. However, the PMs are negligible in regions tens of kilometers from the fault rupture. The PMs of our model are consistent with those of other strike-slip earthquakes, indicating that our piezomagnetic model is reasonable. The east component of observed coseismic geomagnetic changes and calculated PMs on a geomagnetic repeat station located about 6 km from fault trace are +4.8 ± 2.2 nanotesla and +4.3 nanotesla, respectively. It seems that the piezomagnetic model can explain the observed data. The PMs are up to 10 nanotesla in the near-field with the initial magnetization of 3 A/m and stress sensitivity of 2 × 10−3 MPa−1. Consequently, considerable coseismic geomagnetic changes that are above error could be observed along the fault, especially at locations with geometrical complexities.

Highlights

Seismomagnetic anomalies refer to magnetic disturbances associated with seismic activities [1,2]
In order to eliminate the distortion of piezomagnetic anomalies (PMs) resulting from stress concentration and singularity on the fault plane, we do not consider the PMs in the project area of fault slip about 2 km from the fault trace
The total intensity (F) and east component (Y) of PMs are calculated because Y is expected to be significantly changed under the east–west slip regime

Summary

Introduction

Seismomagnetic anomalies refer to magnetic disturbances associated with seismic activities [1,2]. One mechanism of coseismic geomagnetic changes is the piezomagnetic effect caused by the static stress changes due to earthquake rupture [18]. Many observed seismomagnetic anomalies have been explained by the piezomagnetic effect [19,20]. The piezomagnetic effect can be used to explain the secular variation of geomagnetic fields in tectonic active zones, such as subduction zones [21]. The piezomagnetic anomalies (PMs) associated with strong earthquakes in low strain rate regions are more important because coseismic PMs are much larger than those resulting from aseismic tectonic loading [22,23,24]. Coseismic PMs must be investigated and excluded before examining geomagnetic field variations due to aseismic tectonic loadings. New research into PMs has been involved in the early warning of earthquakes, because PMs may be observed earlier than seismic waves [7,26]

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Discussion

Conclusion