On the relationship between forearc deformation, frictional porperties, and earthquake ruptures

During the last decade, three subduction earthquakes with magnitude larger than 8.7 occurred. If the Maule and the Andaman-Sumatra earthquakes have most probably produced limited shallow slip, the 2011 Tohoku-Oki earthquake has generated very large shallow slip challenging the classical model that requires aseismic upper portion. We will investigate if specific frictional properties along the NE Japan megathrust could explain this behavior. To do so, we will retrieve the frictional properties from simple mechanical analysis of long- and short-term deformation of the forearc and compare the results for South Chile, Sumatra and NE Japan. In a second stage, we will confront these properties to dynamic simulations of earthquake cycles. In particular, we will study the possibility that slip near the trench resulted from thermal pressurization on a shallow patch of the megathrust, and investigate whether low-velocity friction on that patch is rate- strengthening or rate-weakening. At last, we will discuss how deformation of forearcs could be used to enhance seismic and tsunamigenic risk assessment.