The Geomagnetic Effect of Earthquakes

Resumo

Based on the results of instrumental observations carried out at a number of mid-latitude observatories of the INTERMAGNET network and at the Mikhnevo Geophysical Observatory (Institute of Geospheres Dynamics, Russian Academy of Sciences), it is shown that strong earthquakes are accompanied by increased variations in the Earth’s magnetic field. In this case, the short-period (period of ~0.5–0.8 min) and long-period (~5–20 min) stages of increased geomagnetic variations are clearly distinguished. The maximum amplitudes of induced geomagnetic variations for short-period and long-period variations are 1.5–2 and 2–4 nT, respectively. Induced geomagnetic disturbances of similar morphology and almost synchronous nature are noted at observatories located at significantly different distances from the earthquake source.