Natural and Experimental Evidence of Melt Lubrication of Faults During Earthquakes

Abstract

Melt produced by friction during earthquakes may act either as a coseismic fault lubricant or as a viscous brake. Here we estimate the dynamic shear resistance (τ f ) in the presence of friction-induced melts from both exhumed faults and high-velocity (1.28 meters per second) frictional experiments. Exhumed faults within granitoids (tonalites) indicate low τ f at 10 kilometers in depth. Friction experiments on tonalite samples show that τ f depends weakly on normal stress. Extrapolation of experimental data yields τ f values consistent with the field estimates and well below the Byerlee strength. We conclude that friction-induced melts can lubricate faults at intermediate crustal depths.