Lithospheric Shear Zones
Deformation at tectonic plate boundaries is possible thanks to shear localization and weakening in the strongest parts of Earth’s rocky layers – the deep, cold, ductile lithosphere. Shear localization requires a positive mechanical feedback: deformation leads to weakening, which leads to faster deformation, which leads to further weakening, etc. What are the microphysical processes responsible for this feedback?
Earthquake Cycles
During and after an earthquake, the deeper portions of tectonic plates respond to abrupt surface motions with sluggish viscous creep, called post-seismic creep. Post-seismic creep redistributes tectonic stresses, which affect the timing and location of future earthquakes. Lithospheric deformation during post-seismic creep is governed by rocks’ transient creep properties, which in turn are governed by the dynamics of crystalline defects, such as dislocations and grain boundaries.
Post-Glacial Rebound
Vertical ground motions caused by redistribution of large loads at the Earth’s surface, such as through melting of ice sheets or building of river dams, can induce significant local variations in sea-level. The associated rapid, geologically speaking, rock flow in Earth’s deeper layers is governed by transient creep properties of the mantle and lithosphere. By understanding the microphysics of transient creep, we can disentangle the effect of vertical ground motions from other factors that affect the record of sea-level changes, such as climate change.