Open Access

Izu detachment hypothesis: A proposal of a unified cause for the Miyake-Kozu event and the Tokai slow event

Earth, Planets and Space201457:BF03351872

Received: 21 June 2004

Accepted: 6 April 2005

Published: 20 June 2014


Based on the fact that interseismic deformation of collision zones is generally described by slip along a detachment at depth, I attempt to interpret the deformation of the Izu collision zone in terms of a detachment model. The systematic deviation of the GPS velocities of the Izu Peninsula (Nov. 1998–June 2000) from the Philippine Sea-Eurasian relative plate motions is fitted by the slip on the detachment at a depth of 15–20 km with a rate of 3 cm/yr. On June 26, 2000, seismo-magmatic activity that started near Miyakejima expanded NW by 20 km close to Kozushima in association with dike intrusion over a few months. The horizontal movements associated with this event, however, spread over wide areas in central Honshu. Simple dike intrusion models cannot explain these movements. To explain these, I hypothesize that a 20 cm of rapid slip occurred on the detachment at the time of this event. The abnormal crustal movements in the Tokai-central Honshu-Kanto region then started after the event. I propose that they represent delayed diffusive transfer of the slip on the detachment over surrounding low viscosity layers, such as nearby rupture zones of great earthquakes.

Key words

Izu Peninsula detachment collision Miyakejima Kozushima Tokai diffusion