Potential relationship between seismo-crustal displacement and EM anomalies

Summary form only given. Seismo-crustal displacements, which are derived from surface displacement data recorded by ground-based GPS stations through a band-pass filter to remove effects of the long-term plate movements, frequency-dependent variations and noise via the Hilbert-Huang transform, can be related with fault parameters and utilized to expose earthquakes in preparation periods that have been reported. Seismo-crustal displacements can be classified into three distinct characteristics from earthquakes in Taiwan and Japan. The first type shows that a region with relatively low-pressure surrounded by areas with relatively high-pressure can be formed in earthquake preparation periods. The second type indicates that earthquake-related stress accumulation is resisted in a region, where will be an epicenter of a forthcoming earthquake. The third type reveals that the crust persistently dislocates in a region before earthquake occurrences. Seismo-EM anomalies are often related with the first type of the seismo-crustal displacements because free electric charges would be trapped within the region forming high-conductivity materials. In contrast, no significant EM anomaly can be found in the second and third types. The results shed light on exposing the causal mechanisms of the seimso-EM anomalies and/or explaining indistinct EM anomalies in earthquake preparation periods.