Tectonic Division in and around the Izu Peninsula Based on the Soft Clustering of Surface Displacement Rate Field.

On the basis of statistical (soft) clustering of a horizontal displacement field from Global Navigation Satellite System, we conduct tectonic classification around the Izu Peninsula, a collisional zone in Japan. We determine the best number of the clusters by a statistical index, and classify 44 observation points into "Fuji cluster", "Southern Izu cluster", "Sagami cluster", or "Oshima cluster". The boundaries between the clusters almost correspond to locations of recent large earthquakes. Although several points differ from a recent concept of the Izu microplate, we obtain the following perspectives: (1) Northern part of the Izu Peninsula is integrated with Honshu, the main island of Japan. (2) Multiple cluster boundaries merge around Izu Tobu Volcano Group. (3) Fault zones of landward extension of subduction trenches (the Suruga Trough and the Sagami Trough) do not correspond to the cluster boundaries. [ABSTRACT FROM AUTHOR]