Effects of a buoyant aseismic ridge on an inter-oceanic subducted slab: case study of the Izu-Bonin-Mariana subduction zone

Abstract

The Ogasawara Plateau is part of the Marcus-Necker Ridge. This plateau impinges upon the trench of the Izu-Bonin-Mariana subduction zone, which is located in the northwest Pacific. The effect of the Ogasawara Plateau on the subducted slab in this region was investigated using seismic tomography as well as 3D tomographic and numerical models. A region of anomalously low seismic velocity detected within the subducted slab beneath the southern Izu-Bonin arc, to the northwest of the impinging Ogasawara Plateau, coincides with a cluster of earthquake hypocentres. Preliminary 3D finite element models of a plateau of varying density embedded in a rolling back subducting slab indicate that this anomalous region could represent a density variation within the slab such as a subducted portion of the plateau, or a region of higher than average strain rate induced by resistance of a portion of the plateau to subduct.