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.

Modelling of stresses that influence glacially triggered faulting has progressed substantially in the last decades with more complex models and improved modelling techniques, incorporation of a variety of relevant processes, better constraints of ice-loading history, higher model resolution and 3D geometries. Some recent developments are collected in this section to portray the scope and variability of numerical modelling relevant to glacially triggered faulting. These range from modelling of the general in situ stress field to studies on the stress field induced by glacial loading and unloading.

An appropriate estimation of the ambient background stress field is crucial for determining the effect of additional ice loading (or unloading) on pre-stressed faults. Contributions from local and far-field stress sources (topography, tectonics) need to be reconciled with in situ measurements from boreholes and fault-plane solutions from earthquakes. We describe the different types of stresses in glaciated regions with a focus on Scandinavia together with the techniques used to incorporate stresses into numerical models.

To model glacial triggering of earthquakes, it is necessary to obtain the spatio-temporal variation of glacial isostatic adjustment-induced stress during a glacial cycled. This can be computed efficiently using commercial Finite Element codes with appropriate modifications to include the important effects of ‘pre-stress advection’, ‘internal buoyancy’ and ‘self-gravity’. The modifications described in Wu (2004) are reviewed for incompressible and so-called materially compressible flat-earths. When the glacial isostatic adjustment-induced stress is superimposed on the background tectonic stress and overburden pressure, the time variation of earthquake potential at various locations in the Earth can be evaluated for any fault orientation. To model more complex slip and fault behavior over time, the three-stage Finite Element model approach of Steffen et al. (2014) is reviewed. Finally, selected numerical examples and their results from both modelling approaches are shown.

The polar region is the area surrounding the Earth’s geographical poles (Antarctica, Arctic). While glacially induced faults are well known in the formerly glaciated areas of Northern Europe, such faults within the Arctic and Antarctica are unidentified, although the theory of their physical mechanism would allow their presence. Mainly, the fact that most of the polar region is covered either by ocean (Arctic) or ice sheets (Antarctica, Greenland) prevents detailed analysis of those regions with respect to glacially induced faults. However, there are several indications that suggest an existence of glacially induced faults in the polar region. Here, we summarize findings about potential glacially induced faults in Northern Canada, Greenland, Iceland and Svalbard on the northern hemisphere and revisit the seismicity in Antarctica.