THE KALININGRAD EARTHQUAKES OF SEPTEMBER 21, 2004

Abstract

The earthquakes of magnitudes ML=5.0 and 5.3 in the Kaliningrad enclave of Russia on September 21, 2004 were unexpected in a very low-seismicity area. The earthquakes caused minor damage in the Kaliningrad enclave, in northern Poland and in southwestern Lithuania, and macroseismic intensities of 6-7 (EMS) close to the epicenters. The earthquakes were felt up to 800 km distance. The events have been located under the central-northern part of the Sambia Penninsula at 16 and 20 km depth. Their source mechanism has been found to be a right lateral strike slip on a direction parallel to the edge of the Fennoscandian Shield and the East European Craton. The possible cause of the earthquakes is discussed. With the glaciotectonic cause unlikely, it seems the earthquakes evidence tectonic patterns, possibly resulting from stress propagating all across Europe from the Mediterranean region. Historical information seems to evidence past seismic activity in the region, which together with the 2004 earthquakes show the need to reassess seismic hazard in the area.