Combining Tectonic Stress Field to Explore the Anomaly of Geomagnetic Transfer Function
The changing magnetic field is the key to connect the regional stress field and the geophysical environment information of the seismogenic area.For example,geomagnetic short-period transfer function reflects the physical information such as the underground resistivity.In order to explore the response of the absolute value anomaly of the real part Ar of the geomagnetic transfer function to the tectonic stress by combining the stress field changes in the study area,we use the bounded influence estimation method to calculate the absolute value of the real part Ar of the geomagnetic short-period transfer function at the Kashgar geomagnetic station.We also use the focal mechanism solution data of the western part of Southern Tianshan mountains and the Western Kunlun area to invert the focal consistency parameters of the study area,since the time series change represents the alteration of the stress field in the study area.The study reveals that when stress increases,the geomagnetic transfer function exhibits synchronous or lagging abnormal changes over time.This suggests that continuous accumulation and enhancement of stress causes a change in the resistivity of the underground medium,leading to alterations in the induced magnetic field.Therefore,it is speculated that stress change is one of the effective factors causing local magnetic abnormal changes,verifying the phenomenon of induced magnetic effect before earthquakes.The study further investigates changes in the stress field and magnetic transfer function before eight moderate to strong earthquakes.Pre-earthquake anomalous changes are observed in six instances,showing good consistency between the two phenomena above.The study has revealed that the response of the absolute value of the real part of Ar in various periods of the geomagnetic transfer function of the Kashgar Geomagnetic station varies depending on the azimuth of the earthquake,possibly related to the anisotropy of the subsurface medium in the seismic source region.
Geomagnetic transfer functionThe stress fieldFocal mechanism consistencyInduced magnetic effect
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