The mechanics of earthquakes is controlled by a spectrum of processes covering a wide range of length scales, from tens of kilometres down to few nanometres. For instance, while the geometry of the fault/fracture network and its physical properties control the global stress distribution and the propagation/arrest of the seismic rupture, earthquake nucleation and fault weakening is governed by frictional processes occurring within extremely localized sub-planar slipping zones. The co-seismic rheology of the slipping zones themselves depends on deformation mechanisms and dissipative processes active at the scale of the grain or asperity. If this is the case of shallow earthquakes, the nucleation of intermediate and deep earthquakes remains enigmatic since it occurs at elevated ambient pressure-temperature conditions which should favour plastic deformation and suppress frictional processes. Though, recent studies on fault rocks of Earth’s lower crust and upper mantle reveal microstructures comparable to those associated with co-seismic slip and off-fault damage in brittle rocks. The study of such complex multiscale systems requires an interdisciplinary approach spanning from structural geology to seismology, geophysics, petrology, rupture modelling and experimental rock deformation. In this session we aim to convene contributions dealing with different aspects of earthquake mechanics at various depths and scales such as:
· the thermo-hydro-mechanical processes associated to co-seismic fault weakening based on rock deformation experiments, numerical simulations and microstructural studies of fault rocks;

· the study of natural and experimental fault rocks to investigate the nucleation mechanisms of intermediate and deep earthquakes in comparison to their shallow counterparts;

· the elastic, frictional and transport properties of fault rocks from the field (geophysical and hydrogeological data) to the laboratory scale (petrophysical and rock deformation studies);

· the internal architecture of seismogenic fault zones from field structural survey and geophysical investigations (e.g. seismic, electric and electromagnetic methods);

· the modeling of earthquake ruptures, off-fault dynamic stress fields and long-term mechanical evolution of realistic fault networks;

· the earthquake source energy budget and partitioning between fracture, friction and elastic wave radiation from seismological, theoretical and field observations.

· the interplay between fault geometry and earthquake rupture characteristics (e.g. coseismic slip and rupture velocity distribution) from seismological, geodetic, remote sensed or field observations;

We particularly welcome novel observations or innovative approaches to the study of earthquake faulting. Contributions from early career scientists are solicited.

Solicited oral presentation: Matthew Tarling (University of Otago)