On the Propagation of VLF Electric Field Emissions Associated with Earthquakes in the Middle Layer of the Earth Crust

An ensemble of elementary radiators is generated on the basement rock because of the applied stresses in the preparation zone of the earthquakes in the earth crust. Considering such an ‘ensemble’ as the source of electromagnetic signals, the strength of the electric field is estimated at different distances and frequencies laying in range (۳ – ۲۷ kHz) at three different conductivities of the crustal layers (۱۰-۸, ۱۰-۹, ۱۰-۱۰ S/m). The results of the computation are presented in this paper. Moreover, propagation distances for the seismogenic VLF emissions have also been calculated in the frequency band (۳ – ۲۷ kHz) at the conductivities laying in the range (۱۰-۸ - ۱۰-۱۰ S/m) within the limit of detectability of measuring instruments (۱۰-۷ V/m). It is observed that these distances increase with the decrease of conductivity of the middle layer of crust. Furthermore, theoretical results of computations are verified from the experimental observations of the seismic event that occurred at the distance of ۶۹۸ km from the observing station at Chaumuhan Mathura (Geographic lat. ۲۷.۴۹۰N, long. ۷۷.۶۷۰E). In addition to this, the generation and propagation mechanisms of seismo-electromagnetic radiations have also been discussed briefly.

کلیدواژه ها:

Attenuation ، earthquake ، Earth crust ، Radiating dipole ، VLF waves