Geomagnetic Variations during Strong Earthquakes

Abstract

We analyze the geomagnetic effect caused by the strong earthquakes using the data from the Geophysical Observatory «Mikhnevo» (MHV) of the Institute of Geosphere of the Russian Academy of Sciences (IDG RAS) and from a number of observatories of the international INTERMAGNET network. It is shown that seismic events are accompanied by characteristic variations in the Earth’s magnetic field. These induced geomagnetic variations contain a clearly pronounced short-period component with a period of ∼0.5–0.8 min which is recorded during shallow earthquakes and a long-period component (∼5–20 min) observed in the most cases. The maximum amplitudes of the induced geomagnetic variations are ∼1.5–5 and ∼2–20 nT for the short-period and long-period components, respectively. It is noted that the induced geomagnetic perturbations recorded by the observatories at significantly different distances from the source of the earthquake feature almost simultaneous and morphologically similar behavior.