The ultra low frequency electromagnetic radiation observed in the topside ionosphere above boundaries of tectonic plates

Abstract

In this paper we present results of a comparison between ultra low frequency (ULF) electromagnetic (EM) radiation, recorded by an electric field instrument onboard the satellite detection of electromagnetic emissions transmitted from earthquake regions in the topside ionosphere, and the seismicity of regions with high and low seismic activity. In particular, we evaluated the energy variations of the ULF Ezelectric field component during a period of four years (2006-2009), in order to examine the possible relation of ULF EM radiation with seismogenic regions located in Central America, Indonesia, the Eastern Mediterranean Basin and Greece. As a tool for evaluating the ULF Ez energy variations we used singular spectrum analysis techniques. The results of our analysis clearly show a significant increase of the ULF EM energy emitted from regions of highest seismic activity at the boundaries tectonic plates. Furthermore, we found that higher electromagnetic radiation was detected in a region above the northern- western Greek Arc (R1) than above the adjacent region including Athens and its urban area. We interpret these results of the present study as suggesting that: i) the seismogenic regions at the boundary of tectonic plates radiate ULF EM emissions observed by satellites in the topside ionosphere; and ii) that this EM radiation is not only related with the occurrence time of great (M≥5) earthquakes, but it is often present in intermediate times and it appears as a quasi-permanent phenomenon.