RECONSTRUCTING FEATURES OF EARTHQUAKE DYNAMICS FROM FIELD AND EXPERIMENTAL OBSERVATIONS

Field and laboratory observations provide clues on earthquake fault mechanics which are complementary to seismological data. We review a few examples where some characters of dynamic rupture can be retrieved, even for faults which have been seismically active in ancient times, in particular for cases where frictional melt occurred. Although melt is not widespread on natural faults, it is produced co-seismically and thus provides a unique tool to deduce faulting and rupture properties during earthquake slip. Coseismic secondary fracture networks provide information on dynamic stress rotation during the passage of fracture tip, allowing to place constraints on rupture propagation velocities and rupture direction. Melt thickness and the microstructure of the non-equilibrium melt boundary on the fault yield constraints on friction, using relatively simple concepts on the frictional work and heat balance. Furthermore we show how, in principle, an indicative seismic slip velocity can be retrieved.