Observational evidence of anisotropic changes apparent resistivity before strong earthquakes

TL;DR

This study provides observational evidence that anisotropic apparent resistivity changes significantly in specific directions before strong earthquakes, potentially aiding in earthquake prediction by analyzing resistivity anomalies.

Contribution

It introduces a method to analyze anisotropic resistivity variations and links these changes to stress azimuths prior to earthquakes, offering new insights into pre-seismic signals.

Findings

Resistivity varies perpendicular to maximum principal stress azimuth

Small fluctuations occur along the maximum principal stress direction

Resistivity anomalies can help estimate earthquake epicenters

Abstract

Using a method based on normalized monthly variation rate, we studied resistivity data of seven observation stations before the events in the epicenter areas of two strong earthquakes. The relationship between variation of anisotropic apparent resistivity and the azimuth of the maximum principal stress is analyzed. The study shows that significant apparent resistivity variation occurs in the direction that is perpendicular to the azimuth of the maximum principal stress while only small fluctuation are recorded in the direction of the maximum principal stress. We surmise that the variation of anisotropic resistivity occurs in the late stage of the development of a strong earthquake, which can be observed in the epicenter area. If the density of the observation stations is increased and the direction of the observed resistivity is right, the epicenter of an earthquake location may be estimated by the observed resistivity anomaly.