Research on Normalized Variation Characteristics of Apparent Resistivity Before Strong Earthquakes

Using Normalized variation rate method, we study the resistivity data of 7 stations in the epicenter areas of 2 strong earthquakes before the events. The relationship between variation of anisotropic apparent resistivity and the focal mechanism solution of earthquake is analyzed. The result 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. Most of the anisotropic resistivity variation 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 can be increased and the direction of the observed resistivity can be appropriately set, the epicenter of an earthquake may be estimated by the observed resistivity anomaly.