Inferring earthquake mechanics using an integrated field and laboratory approach

Understanding the physics of earthquake slip helps to improve seismic hazard predictions. The occurrence of quenched frictional melts along exhumed fault zones (pseudotachylytes) provides unequivocal evidence of ancient seismic slip along these faults [Sibson, 1975]. To understand the evolution of friction (the ratio of shear stress over normal stress) during melt-generating slip events, several experimental studies have been done in recent years. Using results from a slow to high velocity shear apparatus at INGV, Rome, we investigate the evolution of experimental fault strength with increasing displacement, and we correlate variations in fault strength with stress drop. Our results reliably reproduce seismological measurements of stress drop on seismogenic faults where frictional sliding produces pseudotachylyte on the fault plane.