Slow stick slip of antigorite serpentinite under hydrothermal conditions as a possible mechanism for slow earthquakes

Abstract

Slow earthquakes, characterized by a different scaling law to regular earthquakes, have been detected at the hydrated plate interface in the subduction zones, but the generating mechanism of them remains almost unexplored. Frictional experiments on antigorite serpentinite under hydrothermal conditions are conducted to assess the distinct scaling law of slow earthquakes. Slow stick-slip was observed at temperatures that were close to the dehydration temperature of antigorite, which is resulted by the localized dehydration of serpentine in the shear zone. The occurrence of slow stick-slip is consistent with the temperature range found in the corner of the mantle wedge in SW Japan and Cascadia, where slow earthquakes occur. The laboratory slow stick-slip shows a similar scaling law of slow earthquakes, but distinct from that of regular earthquakes. We propose that the shear-induced dehydration of the serpentine play an important role for the generation of slow earthquakes.