Earth Planets Space, Vol. 56 (No. 3), pp. 347-351, 2004LETTER
Kazushige Obara, Yoshikatsu Haryu, Yoshihiro Ito, and Katsuhiko Shiomi
National Research Institute for Earth Science and Disaster Prevention, 3-1 Tenno-dai, Tsukuba, Ibaraki 305-0006, Japan
(Received November 30, 2003; Revised February 16, 2004; Accepted February 16, 2004)
During the sequence of aftershock activity of the 2003 Tokachi-Oki earthquake, anomalous events predominant in low-frequency components occurred very close to a subducted seamount around the junction between the Kuril Trench and the Japan Trench. The low-frequency wave train in the coda part reflects the strong excitation of surface waves and the source depth is considered to be very shallow. The focal mechanism of the low-frequency event is a type of the reverse fault. Considering with the source depth and the mechanism, the low-frequency event might have occurred on the plate boundary as a dynamic process of the tectonic erosion by the subducted seamount.
Key words: Low-frequency earthquake, 2003 Tokachi-Oki earthquake, subduction zone, tectonic erosion, seamount, plate boundary..