Ionospheric propagation of ELF/VLF waves radiated from earthquake

Anomalous phenomena associated with earthquakes have been reported using satellite observations. Before earthquake generation, electromagnetic wave emissions are frequently observed as high noise levels in wide bands. We compute rigorous wave intensities on the ground surface and in the ionosphere caused by earthquakes, using full-wave analysis. We assume the seismic source is an electric dipole located underground as the combination of much smaller dipole polarizations created around the epicenter. The inhomogeneity of the ground and the inhomogeneity and anisotropy of the ionosphere are taken into consideration. Especially, the effects of the geomagnetic field on the wave propagation are considered. The computed results in the frequency range from 10 Hz to 10 kHz show the difference in spatial distributions of the wave intensities due to the whistler-mode propagation in the ionosphere. By using these results, the wave intensities which would be observed on the Earth's surface and in the ionosphere are determined as a function of seismic source strength.