Observation and Analysis of Anomalous Terrestrial Diffraction as a Mechanism of Electromagnetic Precursors of Earthquakes

Detection of earthquake precursors has long been a controversial issue with regard to its possibility and realizability. Here we present the detection of electromagnetic anomalous signals before large earthquakes using an observation network of very high frequency radio wave receivers close to major tectonic lines in Japan. The receivers are equipped with specifically designed narrowband filters to suppress noises and to detect extremely weak signals. We detected different types of electromagnetic anomalies before earthquakes around mountainous and coastal regions, where presence of electric charges is anticipated on the surface located in the middle of the radio wave paths near major tectonic lines in Japan. We use numerical electromagnetic wave analysis to show that when electric charges are present on a ground surface as a consequence of tectonic activity, the surface charges interact strongly with radio waves and eventually cause strong diffraction of the radio waves. The analysis was performed using the three-dimensional finite-difference time-domain method with digital elevation models of the actual geographical landforms on a massively parallel supercomputer. The results confirm the consistent mechanisms of the electromagnetic precursors, which explains the anomalous electromagnetic signals observed by the authors before large earthquakes. Possible electromagnetic precursors of earthquakes has been detected by observation networks placed near major tectonic lines in Japan. We have observed radio waves from many sources for several years, and anomalous electromagnetic diffraction has been considered as the precursors of earthquakes. We also consider the mechanism of the signals, and found that anomalous electromagnetic diffraction occurs shortly before earthquakes. The behavior of the radio wave has been confirmed also by various computer simulations. A low-noise high-sensitivity technique is proposed to observe anomalous radio wave signals associated with earthquakes Possible electromagnetic precursors of earthquakes have been detected by observation networks placed near major tectonic lines Large-scale numerical analysis has suggested that anomalous diffraction is the mechanism of the electromagnetic precursors