Frictional properties of megathrust gouges

To better understand and more reliably model subduction zone seismogenesis, we determined the frictional properties of previously obtained natural megathrust fault gouges from exhumed subduction zone sediments exposed on Shikoku Island, Japan. These gouges correspond to peak paleo-temperatures of 105°C to 470°C, representing different stages in the diagenetic and metamorphic evolution of the subducted sediments and covering the aseismic zones as well as the seismogenic zone. We determined the frictional characteristics of these materials at the sample-specific, approximate peak in-situ PT conditions, i.e. the PT conditions corresponding to the maximum burial depth of these samples, applying pore fluid overpressure ratios of 0.65 or 0.90. The experiments were performed using the ring shear machine at Utrecht University.