Electromagnetic Signals Associated With Earthquakes

There are numerous independent reports on the electromagnetic changes possibly associated with earthquakes. Such information has been adopted in some prediction test of earthquakes. But due to the complicated seismogenic process and the limited understanding of the above phenomena, there are active debates on the electromagnetic signals and their relationship with earthquakes. Thus, a physics-based study would be helpful for understanding seismic electromagnetic phenomena and strengthening their applications. In this chapter, we give a brief review of the observation, data processing, and possible mechanisms of seismic electromagnetic signals. As a potential physics-based approach, we propose an integrated research scheme, taking into account the interaction among observation, methodology, and physical model. The main approach includes the following key problems: (1) how to perform a reliable and appropriate observation with some clear physical quantities; (2) how to develop a robust methodology to reveal weak earthquake-related electromagnetic signals from noisy background; and (3) how to develop plausible physical models based on theoretical analyses and/or laboratory experiments for the explanation of the earthquake-related electromagnetic signals observed in the field conditions. This study provides some overview of the study on electromagnetic signals associated with earthquakes and stimulates the related study toward a physics-based stage.