Investigating controls from surface loading variations on seismicity in continental interiors

Although typically characterised as 'stable', continental interiors do experience intermittent seismicity in discrete, localised regions. In addition, whilst overall tectonically-driven strain-rates in such settings are low, typically <10-9 yr-1, and often too slow to be observable with modern geodetic techniques, the interior regions of continents are often subject to transient deformation driven by non-tectonic variations in surface loading, such as the redistribution of ice, sediment, or water masses. The transient deformation signals resulting from these processes occur on a range of timescales, and often with magnitudes and rates that are far larger than those of processes taking place on geological timescales in such tectonically quiescent settings. As such, even in settings where their magnitude is insufficient to lead to seismicity without a tectonic influence, they may play a significant role in determining the temporal distribution of earthquakes that are the overall result of slower, longer term, tectonic processes, and serve to modulate any 'earthquake cycle'. Here, we use examples from intraplate North America to investigate the stresses and strains induced by climatically-controlled variations in hydrological surface loading, and how these may trigger and/or modulate the seismicity of the plate interior. We combine seismological and geodetic observations to inform models for the interaction between seismicity and non-tectonic transient deformation, and consider the implications of this for the earthquake cycle in plate interiors and fault rheology in such intraplate settings.