What Caused the 2011 Tohoku-Oki Earthquake? : Effects of Dynamic Weakening

Abstract

Some observational studies have suggested that the 2011 great Tohoku-Oki earthquake (M_w9.0) released a large portion of the accumulated elastic strain on the plate interface owing to considerable weakening of the fault. Recent experimental and theoretical studies have shown that considerable dynamic weakening can occur at high slip velocities because of thermal pressurization or thermal weakening processes. This paper reviews several models of the generation of megathrust earthquakes along the Japan Trench subduction zone, that considers thermal pressurization or a friction law that exhibits velocity weakening at high slip velocities, and it discusses the causes of megathrust earthquakes. To reproduce megathrust earthquakes with recurrence intervals of several hundreds of years, it will be necessary to consider the existence of a region at the shallow subduction plate boundary where significant dynamic weakening occurs due to thermal pressurization or other thermal weakening processes.