Abstract
The plate boundary fault between Philippine Sea plate and Honshu plate is the source of the Kanto earthquake of 1923 in the central Japan. It is important to identify the geometry of the plate boundary. In this study, a N-S trending tear of the seismogenic zone was identified beneath the Tanzawa Mountain with three dimensional GIS analysis for earthquake data. This is a slab tear of the subducted lower crust of the Izu arc which is the uppermost layer of Philippine Sea slab. The Philippine Sea slab beneath the western half of the Tanzawa Mountain is much deeper than the slab depth beneath the eastern half of the Tanzawa Mountain. The position of the slab tear shows a spatial link to the predicted western margin of the earthquake source fault of the Kanto earthquake of 1923. The identified complex geometry of the plate boundary can be used to predict hazardous earthquakes of the Tokyo metropolitan region.
