The Influence of hydrospheric processes on intraplate seismicity
About the Event:
The capacity for short-term non-tectonic processes, both natural and anthropogenic, to influence the occurrence of earthquakes in either active tectonic settings or in ‘stable’ plate interiors, remains a subject of much debate. In particular, much recent work has focused on the potential for long-wavelength changes in continental water storage to produce observable surface deformation, and to impact on regional earthquake occurrence and seismicity rates on a range of timescales.
Previously demonstrated short-term variations in seismogenic behaviour due to surface or near-surface hydrospheric processes are typically limited to active plate-boundary regions (California, the Himalayas, the Japanese Archipelago). In all of these environments, seismicity is the result of observable and ongoing tectonic processes, and the stresses due to water load variations are significantly smaller than the secular rates of stress accumulation. Continental interiors present a different scenario, where secular stressing rates are low or negligible – often less than would be expected to result from short-term surface processes. However, any modulating hydrological influence has been difficult to identify in intraplate earthquake sequences.
In this presentation, I will draw on observations of the variation in hydrological load in the central United States – a slowly-deforming plate interior - based on a combination of surface hydrology and satellite gravity, and demonstrate how we can use these observations to explain short term geodetically-observed solid-Earth deformation in this area. I will then show how the stress field induced by these migratory hydrological loads links this induced surface deformation to temporal variations in the seismicity rate, and discuss the implications of this for the mechanics of faulting in plate interiors.
About the Speaker:
Tim is a Royal Society University Research Fellow at the Institute for Geophysics and Tectonics, University of Leeds in the UK. He completed his PhD at the University of Cambridge in 2013, looking at ways to used earthquake locations to constrain the brittle behaviour and structure of the lithosphere. After this, he worked as a postdoc at the Ecole Normale Superieure in Paris, looking at intracontinental deformation across a range of timescales, before returning to the UK in 2015, on an independent research fellowship funded by the Royal Commission for the Exhibition of 1851. Much of his work focuses on earthquakes that occur within (rather than between) plates, in both continental and oceanic settings, where he uses a combination of seismology, geodesy, and geodynamic modelling to constrain earthquake source processes and the forces that drive their occurrence. Current focuses include the seismicity associated with the deformation of shallow subjecting slabs, and the ways in tectonic and non-tectonic processes interact, and how this may impact on seismicity.