Time-varying behaviour of fault systems and seismicity

Funder: Royal Society

The tectonic processes that form the features of the Earth, from mountain ranges to ocean basins, act over millions of years, and the continent-scale forces that drive these processes are often viewed as being unchanging on this timescale. However, we are starting to recognise that these processes do not act in isolation, but interact with shorter-timescale variations that arise from other, non-tectonic, sources. The most commonly-recognised influences are climatic (largely due to the movement of ice and water across the Earths’ surface), and man-made (mainly the injection or extraction of fluids into the Earths’ crust). The vast motions of plate tectonics are localised into narrow zones, breaks in the Earths’ crust, called faults. Motion on these faults takes place through slow sliding, with the fault creeping along at a rate of millimetres per year, or through potentially-catastrophic failure in earthquakes, where faults may move meters within seconds. This project is looking into how external ‘non-tectonic’ factors, particularly those relating to large-scale change in ice and water volumes, may cause variations in either the rate of creep on sliding faults, or on the earthquakes-rate, in a range of settings around the world. In a rapidly-changing world, a better understanding of how these short-term processes may influence underlying tectonic processes is critical for our ability to quantify seismic hazard. Additionally, the sensitivity of faults to short-term variations in the forces applied to them opens a new and exciting avenue to probe the physics behind the faulting process and the initiation of earthquakes.