Seismo Electromagnetics and Earthquake Prediction: History and New directions

Abstract

This review will focus on earthquake (EQ) precursor studies for EQ prediction. Among the long-, medium-, and short-term EQ predictions, the most meaningful are short-term predictions because of their immediate effect on human lives. Investigations of EQ precursors were very scarce before the 1995 Kobe EQ, but various kinds of precursors were reported for this disastrous Kobe EQ. Then intensive observations and studies were initiated after the Kobe EQ in different countries, especially in Japan in collaboration with two Japanese frontier projects engaged in seismo-electromagnetic studies during the years of 1996-2001 which contributed very much to the progress of precursor studies. Electromagnetic phenomena in possible association with EQs have been reviewed with special reference to those achievements made during and after the frontier projects. Being stimulated by the success of these Japanese frontier projects, national precursors studies devoted to EQ prediction have been developed in different countries. The most important findings during the past two decades are that many of short-term EQ precursors are non-seismic (electromagnetic, geochemical) rather than seismological, and that the ionosphere (both the lower and upper layers) and atmosphere are perturbed prior to an EQ, being coupled to the lithosphere (the presence of lithosphere-atmosphere-ionosphere coupling). As recent research activities, we will present the precursors for the recent 2011 Tohoku mega-EQ, not only electromagnetic but also of ground movements. Finally, future directions of EQ precursor studies and short-term EQ prediction will be extensively discussed with paying particular attention to the importance of multidisciplinary and multi-parameters observations and critical analyses.