Model of Electromagnetic Manifestations of Nearby Moderate Earthquakes

摘要

Using a numerical model of the ELF radio wave scattering by a localized non-uniformity of the air conductivity profile, we evaluate the earthquake (EQ) impact on the power spectra of global electromagnetic (Schumann) resonance. The seismogenic non-uniformity is introduced above the moderate earthquake of magnitude M = 5.5. The disturbance corresponds to the downward shift of regular conductivity profile by 16.5 km it is axially symmetric and it varies along the radius from the EQ hypocenter according to the Gauss law with the scale of 245 km. The observer is found at the Nakatsugawa observatory (Japan), geographic coordinates 35.420° N and 137.53° E. The non-uniformity occupies positions at distances of 0, 100, 200, 300, 400, and 500 km from the observer to the east. Three positions of field source are considered: Asia (0° N and 105° E), Africa (0° N and 25° E), and America (0° N and 75° W). The electromagnetic problem is solved with the help of the complex characteristic electric and magnetic heights relevant to conductivity profiles. These heights are found by solving the Riccati equation and are substituded into the two-dimensional telegraph equations (2DTE) for computing the vertical electric and two orthogonal horizontal magnetic fields in the Earth–ionosphere cavity. To single out the spectral modifications at particular frequencies, we compare the power spectra of the regular and the disturbed cavities. Finely, dependence is obtained of the field modifications versus distance to the EQ hypocenter.