Deep structure, volcanism and Wadati-Benioff zone of the northwestern pacific convergent margin

Abstract

The morphology of the Wadati-Benioff zone in the region of Kamchatka, the Kurile Islands and Hokkaido, based on the distribution of 6319 earthquake foci, has verified the existence of an intermediate-depth aseismic gap and its relation to active andesitic volcanism. It appeared that deep-focus earthquakes in this region belong to a paleosubduction zone activated by an intermediate-depth collision with the active subduction zone in the area of Hokkaido. A system of deep seismically active fracture zones was delineated in the continental plate and confirmed by the results of deep seismic sounding. Two of these fractures, dipping toward the subduction zone, may be considered as the principal feeding channels for active and Holocene volcanoes of the continental volcanic bels of Kamchatka.