アイテム詳細

要旨

We investigate earthquake potential of megathrust earthquakes in Peru based on the interseismic coupling model at the subduction interface (ISC) (Villegas-Lanza et al. 2016). Northern Peru displays a shallow and weak ISC, whereas Central and Southern Peru are highly coupled. Recent studies in the Nankai-Tonankai subduction region in Japan indicate that slip deficit regions do not directly reflect the local frictional strength characteristics controlling fault slip behavior at the plate interface (Noda et al. 2021). Therefore, to investigate the necessary conditions for megathrust earthquake generation we calculate the difference between accumulated strain energy during the interseismic period, with fault fracture energy (G), for a given slip scenario. A scenario cannot occur unless the accumulated strain energy exceeds G. To calculate G we use a scaling between average fault slip and G for subduction interface earthquakes, obtained from the NEIC global dataset of finite fault slip rupture models (Hayes et. al, 2017), and the 2D finite width slip dynamic rupture model (Pulido 2022). We calculated the shear stress accumulation rate and total accumulated shear stress at the Peruvian subduction margin, based on the slip deficit rate model, and interseismic periods since the largest historical earthquakes for the Northern, Central and Southern segments of the subduction interface. Our results indicate that the Central segment in Peru has currently accumulated the largest amount of shear stress, corresponding to an earthquake up to Mw~8.8. Using the earthquake energy balance we quantified the necessary conditions for megathrust earthquake generation across the subduction margin in Peru.