The Belchatow, Poland, earthquakes of 1979 and 1980 induced by surface mining

Abstract Five seismic events occurred between August 1979 and May 1980 in the Belchatow trench area in central Poland, where large brown-coal deposits have been surface-mined since 1976. The three largest shocks had a local magnitude M L = 3.5 , seismic moment M o = 1.5 · 10 14 N-m and source radius r = 350m , approximately. The tremors had maximum intensity between 5 and 6, and from the magnitude—intensity—depth relation, the focal depth was estimated to be between 1 and 5 km. The Belchatow tremors are the manifestation of an unusual type of induced seismicity, i.e., seismicity connected with surface mining. The removal of overburden and extensive ground-water withdrawal by the mining operations seem to be direct factors responsible for stress concentration, although preexisting tectonic stress might be the most important indirect factor responsible for the origin of these events.