A long-term slow slip event from 1996 to 1997 in the Kii Channel, Japan

Akio Kobayashi

doi:10.1186/1880-5981-66-9

Abstract

We present a long-term slow slip event from 1996 to 1997 in the Kii Channel along the Nankai Trough in southwestern Japan that has not been reported previously. The long-term slow slip event had a moment magnitude Mw 6.7 and a duration of 1 to 1.5 years. The magnitude of the event was smaller than those of the Tokai (Mw 7.1) and the Bungo Channel (Mw 7.0 to 7.1) events along the Nankai Trough. The slip was located slightly shallower than the depth of the low-frequency earthquakes around the Kii Channel. Long-term slow slips have been identified in various regions along the Nankai Trough, except in the Kii Peninsula. Unveiling the history of long-term slow slips is expected to contribute to an understanding of plate boundary characteristics as well as to the prediction of large earthquakes along the Nankai Trough.

Highlights

Various types of slow slip events (SSEs) have been reported along subduction plate boundaries
Low-frequency tremors along the Nankai Trough are distributed in a belt-like zone at depths of about 30 km on the plate interface, and a distinct gap occurs in the Kii Channel (Obara 2009)
Along the Nankai Trough, including the southern Kii Peninsula, it is Conclusions In this paper, we have reported on a long-term slow slip event that occurred from 1996 to 1997 in the Kii Channel along the Nankai Trough in southwestern Japan

Summary

Introduction

Various types of slow slip events (SSEs) have been reported along subduction plate boundaries. These events tend to exhibit large variations in duration, magnitude, and recurrence behavior (Schwartz and Rokosky 2007). Along the Nankai Trough of Japan, Hirose et al (1999) detected a SSE with a duration of 1 year in the Bungo Channel region. In Cascadia, Dragert et al (2001) documented a SSE that lasted for a period of several weeks. Obara et al (2004) reported SSEs in the Shikoku area of Japan that lasted for several days and were accompanied by non-volcanic deep lowfrequency tremors, which are referred to as episodic tremor and slip (ETS) (Rogers and Dragert 2003). SSEs have been reported in Mexico (Lowry et al 2001), southern Alaska (Freymueller et al 2002), New Zealand (Douglas et al 2005), and Costa Rica (Protti et al 2004)

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Conclusion