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GEOMAGNETIC ANOMALIES ASSOCIATED WITH EARTHQUAKES

С. А. Рябова

Abstract

The purpose of the present study is to examine the geomagnetic anomalies possibly linked with seismic activity. We analyzed the geomagnetic data recorded at the Mikhnevo Geophysical Observatory (54.959?N, 37.766?E) and INTERMAGNET Magnetic Observatories in order to discover anomalous geomagnetic variations associated with the high-magnitude earthquakes. The magnetic field variations were analyzed during seismic events that occurred in different regions with a magnitude greater than ~ 5. It was established that at the final stage of the preparation of the focus and with the main shock, magnetic field perturbations are recorded. At the same time, geomagnetic variations are manifested in two forms: short-period, occurring within 5 ? 15 min after the main shock and long-period, the beginning of which is recorded either immediately after the short-period, or 5 ? 20 min before the main shock. For shallow focus earthquakes we observed both short-period (period of ~ 0.5 ? 0.8 min) and long-period (period of ~ 5 ? 20 min) geomagnetic disturbances. The maximum geomagnetic anomaly amplitude is 1.5 ? 2 nT for short-period variations and 2 ? 4 nT for long-period variations. For deep focus earthquakes we observed only long-period geomagnetic disturbances. Observations of the local variations in the geomagnetic field have afforded us some evidence that the observed geomagnetic anomalies are linked with the high-magnitude seismic events.

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DOI resolver: doi.org/10.5593/sgem2019/1.1/s05.102

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