Recent studies have shown that the low seismicity of northern Germany is characterized by fault activity caused by the decay of the Late Pleistocene (Weichselian) ice sheet. Several faults and fault systems show evidence of neotectonic activity, all of which are oriented parallel to the margin of the Pleistocene ice sheets. The timing of fault movements implies that the seismicity in northern Germany is likely induced by varying lithospheric stress conditions related to glacial isostatic adjustment, and the faults thus can be classified as glacially induced faults. For the Osning, Harz Boundary and Schaabe faults, this is supported by numerical simulation of glacial isostatic adjustment-related stress field changes. Glacial isostatic adjustment is also a likely driver for the historical and parts of the recent fault activity. Glacial isostatic adjustment is also described for the Alps, but it is difficult to clearly distinguish between reactivation of faults in the foreland of the Alps due to the Alpine collision and glacial isostatic adjustment.

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 chapter summarizes the book with a focus on the future of glacially triggered faulting research. The concept of glacially triggered faulting is challenged by new results from Fennoscandia documenting several episodes of fault rupture within the past 14,000 years. We speculate that some of these ruptures at known (or potential) glacially induced faults may not be due to glacially triggered faulting but may contain a signature of tectonically driven intraplate seismicity. Glacially triggered faulting cannot be totally ignored though for these episodes, since the ongoing rebound of the lithosphere is continuously increasing glacially induced stresses that can eventually be released under favourable conditions. As those conditions can only be described by a complex 4-dimensional model, simple identification of glacially induced faults is hampered. Precise dating of the younger fault ruptures is especially important to produce the necessary spatiotemporal image. The intended DAFNE drilling and subsequent in situ observations of the Pärvie Fault combined with numerical modelling will contribute to an improved understanding of the fault mechanism.

The reactivation of glacially induced faults is linked to the increase and decrease of ice mass. But, whether faults are reactivated by glacially induced stresses depends to a large degree on the crustal stress field, fault properties and fluid pressures. The background (tectonic and lithostatic) stress field has a major effect on the potential for reactivation, as the varying stresses induced by the ice sheet affects the state of stress around the fault, bringing the fault to more stable or more unstable conditions. Here, we describe the effect of glacially induced stresses on fault reactivation under three potential background stress regimes of normal, strike-slip and thrust/reverse faulting. The Mohr diagram is used to illustrate how glacially induced stresses affect the location and the size of the Mohr circle. We review these different cases by applying an analysis of the stress state at different time points in the glacial cycle. In addition, we present an overview of fault properties that affect the reactivation of glacially induced faults, such as pore-fluid pressure and coefficient of friction.