Seismicity in Poland in the light of historical records

Polandisacountry of low seismic activity and return periods of earthquakes are long. Thus, historical records of seismic events are here the main source of information. Earthquake catalogue since XVI century, without foreshocks and aftershocks, is listed. Epicenters of seismic events are distributed mainly in southern Poland along Sudetes and Carpathians, and in central and northwestern Poland, generally along the Teisseyre-Tornquist Zone. The historical data from the Precambrian Platform in northeastern Poland, and from the Fore-Sudetic Block and the Carpathian Foredeep are too poor for evaluation of earthquake parameters with sufficient accuracy. The Orawa-Nowy Targ Basin in the Carpathians is the best seismically recognized region in Poland. A series of seismic events occurred on November 30, 2004, with the main earthquake of magnitudeM=4.4 and epicentral intensity Io = 7 in the EMS-98 scale, caused even damage to buildings. Similar events were recorded there in years 1935 and 1717. The Kaliningrad earthquakes of M = 5.0 and M = 5.2 on September 21, 2004 occurred in the area of the Precambrian Platform supposed to be aseismic. The earthquakes caused slight damage to individual buildings in more than 100 localities in northern and northeastern Poland. The seismicity of Poland can be only well recognized by monitoring of micro shocks, i.e. seismic events of M << 2 by arrays of local seismic stations located both in active and supposedly aseismic areas