Poland is in an intraplate area characterized almost everywhere by low recent tectonic activity. This does not imply, however, that earthquakes have not affected it, even in the – geologically speaking – recent geological past. This is due to Pleistocene glaciations, which left traces in the form of earthquake-induced deformed layers. The strongly deformed layers (seismites) as well as some fault zones with significant offsets crossing also Quaternary sediments can indicate fault (re-)activation due to glacial isostatic adjustment. We inventory and describe the five sites/areas in the intraplate northern and central parts of Poland where traces of glacial isostatic adjustment occur. We do not deal, however, with the mountain areas of southern Poland, because Alpine pressure and glacial isostatic adjustment may each, possibly jointly, have acted there as a trigger; distinguishing between traces left by them is not yet viable.

This section presents a detailed overview of soft-sediment deformation structures of possibly seismic origin in the Eastern Baltic Region. Recent studies of soft-sediment deformation structures discovered in Estonia, Latvia, Lithuania, Belarus and the Kaliningrad District of Russia demonstrated that their formation could have been caused by fluidization and liquefaction of sediments possibly triggered by palaeoearthquakes; thus, they could be interpreted as seismites. An identification of corresponding seismogenic faults is complicated though due to the rather small scale of the tectonic dislocations in the intracratonic area with up to 2.5-km thick Phanerozoic sedimentary cover. Nevertheless, a part of soft-sediment deformation structures can be interpreted as seismites and attributed to the seismic events triggered by glacial isostatic adjustment of the lithosphere during the Last (Weichselian) glacial advance and subsequent deglaciation.