Electromagnetic radiation, possibly associated with earthquake occurrences in the Earth's crust, can be treated as a problem of electromagnetic induction within a conducting half-space representing the crust. We estimated the magnitude of the electric field near the Earth's surface for oscillating electric current dipole sources located at various depths. This shows that the electric field highly attenuates, as expected, and the source must be stronger than 105 A · m, even if it is located at a depth of several kilometers, for practically detecting signals at frequencies in the ULF (ultra-low frequency) range. We also examined the electric field near the Earth's surface for a box-car type source in uniform and non-uniform crust models. We found that the wave form of the source is rather well preserved in both models but signal amplitudes are very small and unlikely to be drastically enhanced even in a non-uniform crustal structure, although this discussion is based only on a specific non-uniform model.
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