How variations in intraplate stresses affect slip and dilation tendencies of faults: The onshore United Kingdom example

Stresses in plate interiors vary in magnitude and orientations on various scales, implying that shear and normal stresses on faults may vary regionally. The effects of intraplate regional stress variations are analysed using a recent compilation of in-situ stress to calculate slip and dilation tendencies of United Kingdom onshore faults. The tendencies are normalised to maximum possible values. Stress in UK can be characterised by a strike slip stress field with variable orientations of maximum horizontal stress, S H . Throughout southern UK, S H is orientated NW, giving rise to very low slip and dilation tendencies on NE striking Caledonian faults. North and E to ESE striking faults have very high slip tendencies, and intermediate dilation tendencies. At a major boundary in stress orientation (the Highland Boundary Fault in Scotland), S H changes abruptly to a northerly trend. Steeply dipping Caledonian faults in northern UK such as the Great Glen Fault have very high slip tendencies and intermediate dilation tendencies. Faults with low dips (e.g. the Moine Thrust) have intermediate slip and dilation tendencies. The dramatic change in slip tendencies on steeply dipping Caledonian faults from southern to northern UK illustrates some of the profound consequences of regional scale stress variations. These conclusions are robust to reasonable uncertainties, but the coarse results of this study indicate that more detailed knowledge of stress and fault geometry is necessary for applications such as pump-storage schemes, nuclear power plants, radioactive waste disposal, mining, and carbon sequestration, as well as for seismic hazard analysis.