Earthquake mechanisms: roles of fluids and stress transfers in shallow to deep seismicity
Convener: Thomas P. FerrandECSECS | Co-conveners: Lisa EberhardECSECS, Sascha ZertaniECSECS, Natalia NevskayaECSECS, Revathy M. ParameswaranECSECS, Mattia GilioECSECS, Friedrich HawemannECSECS

A detailed understanding of earthquake processes plays a significant role in evaluating seismic hazard. Hence, it is crucial to unravel the mechanisms and conditions of rock failure, and the interplay between mineral- and tectonic-scale processes. In nature as well as in the laboratory, seismic ruptures have been observed fossilized as pseudotachylytes (i.e. solidified melt along coseismic faults), which does not exclude alternative processes in the case of ruptures that would not require melting (e.g. thermal pressurization in fluid-rich fault zones). Key information can be extracted from off-fault damage, including micro-scale fracturing of mineral grains, heat-induced transformations, and cyclic switches between brittle and ductile deformation. Several processes have been suggested to trigger mechanical instabilities and/or favor rupture growth, such as fluid percolation events, stress amplifications due to mineral reactions or geometrical complexities, but also grain size reduction, thermal runaway, or variations in strain rate.
While observational methods help image mechanical instabilities, laboratory experiments provide insights into the physics of the lubrication processes enabling seismic faults to grow under pressure. This session aims at facilitating transdisciplinary scientific discussions between all schools of research that address rock failure or related processes from the shallow crust down to the bottom of the upper mantle. We aim to consider and distinguish all stages of the rupture process (trigger, nucleation, propagation, and arrest) from crystals to tectonic plates. This session brings together contributions from various disciplines, including field geology, experimental geophysics, petrology, mineral physics, thermodynamics, seismology, and numerical modelling to discuss how, why, and when rocks break (or not).