Impact of deglaciation on present-day intraplate seismicity in eastern North America and western Europe

The retreat of major ice sheets in North America and northern Europe caused a large-scale isostatic desequilibrium of the lithosphere–asthenosphere system. As a result, formerly glaciated areas started to uplift and lithospheric bending occurred, especially near ice margins. While it is well known that post-glacial uplift continues until present-day in formerly glaciated areas, so has the associated flexure of the lithosphere. This continues to alter the stress state in the areas surrounding the former ice sheet. We have addressed the question of the impact of deglaciation on intraplate stress and seismicity in two separate studies. In one study, we have mapped out and modeled the stress field in the Norwegian sector of the Northern North Sea, a prominent hydrocarbon region in the vicinity of the edge of ice sheet that covered Fennoscandia until $\text{∼20}\text{000}$ years ago. In the other study, we investigated the influence of lithospheric flexure as the possible cause of the anomalously high seismicity in the New Madrid Seismic Zone in the central United States. This was the site of three extremely large (M∼8) earthquakes in 1811–1812, following several previous large earthquakes in Holocene time. As there is no significant deformation of Tertiary sediments in the area, deglaciation appears to have been a trigger for recent seismicity.