How Friction and Pore-Fluid Pressure Conditions Controlled by Fault Mineral Composition Affect Earthquake Rupture Propagation

AbstractAlthough direct recovery of frictional features of fault rocks through drilling projects and multiple experimental analyses, such as the Japan Trench Fast Drilling Project and the Nankai Trough Seismogenic Zone Experiment have been recently performed, the conditions of rupture propagation to levels of friction and pore-fluid pressure remains uncertain. In order to invest such issues, we performed dynamic rupture simulations based on experimental friction datasets measured in fault rocks on the Nankai Trough that was ruptured during the 1944 Mw8.0 Tonankai earthquake. A steady-state friction triggered large slip (about 30 m) near the trench, whereas a high friction suppressed the rupture. The condition in which the pore-fluid pressure was nearly equal to the lithostatic stress decreased the slip about 25 m in case of low friction. However, in case of high friction with negative stress drop, the slip reached to around 20 m, because the low shear strength did not arrest the inertial motion of rupture propagation. Such differences in fault-rock properties and fluid conditions, controlled by fault mineral composition, may fundamentally influence on the complexity and the variability of rupture propagation.