Earth Planets Space, Vol. 52 (No. 8), pp. i-viii, 2000

Recent seismic activity in the Miyakejima and Niijima-Kozushima region, Japan—the largest earthquake swarm ever recorded—

Japan Meteorological Agency

Otemachi 1-3-4, Tokyo 100-0004, Japan

(Received September 1, 2000; Revised September 6, 2000; Accepted September 7, 2000)

Abstract: Seismic activity suddenly started on June 26, 2000 beneath Miyakejima, a small volcanic island located on the Izu-Bonin island arc. Then a series of swarm activity migrated toward the northwest to adjacent volcanic islands, Kozushima and Niijima, with intermittent quiet periods and spatial shifts of active areas. During the period from June 26 to the end of August, numerous earthquakes occurred, including five earthquakes of magnitude 6.0. Here we present the outline of the swarm activity, in particular its spatio-temporal characteristics.