The Detection Depth of Symmetric Four‐Electrode Resistivity Observation in/Near the Epicentral Region of Strong Earthquakes

Abstract

AbstractIn consideration of China's observation of apparent resistivity at fixed sites with fixed electrode array for earthquake monitoring and prediction, we produced the theoretical detection depth for the symmetric four‐electrode resistivity observation in the half‐space of sloping and anisotropic medium, and researched the depth to detect the precursory changes in apparent resistivity related to earthquakes, and thus, obtained the following results: (1) In the late preparation period of strong earthquakes, the changes in apparent resistivity in the underground deep place could be recorded in/near the epicentral region and the detection depth is deeper or far deeper than that in the homogeneous medium; (2) The detection depth is different for different earthquakes in magnitude, epicentral distance and in different measuring direction or during different periods of earthquake preparation, the difference is significant or even very large, and the depth varies dynamically with different seismogenic period. Besides, we discussed the problems of the complexity of precursory changes in apparent resistivity and the geoelectrical structure of the station site in observation of apparent resistivity based on the theoretical detection depth.