Electromagnetic ELF radiation from earthquake regions as observed by low-altitude satellites

Abstract : Seismo-Electromagnetic (SEM) waves observed by low-altitude satellites passing over seismic regions were studied. The data of the COSMOS-1809 satellite were analysed over the earthquake region in Armenia during the period from January 20 to February 17, 1989. Intense EM radiation at frequencies below 450 Hz was observed at the L-shells of the earthquake, during 12 orbits out of the 13 that passed within 6 ø in longitude from the epicenter, and during 1 out of 6 in the range of 6o-8 ø longitude away from this region. The other orbits, which passed 10ø-12 ø from the epicentre, showed no effect. To complete this study, we used the emissions observed by another low-altitude satellite (AUREOL-3). It is shown that during the event the seismic region is permanently radiating; the intensity and the envelope shape of the wave depend on its time relatively to the time of the earthquake. Their frequency spectra are compared to the average spectrum recorded in the same geomagnetic regions. Similar wave intensities and spectral distributions were observed on the two satellites during the seismic periods.