Spatial and temporal evolution of the long-term slow slip in the Bungo Channel, Japan

Abstract

The Global Positioning System network in Japan detected a transient in the Bungo Channel, Japan, in 2009. Time-dependent analysis suggests that between May and September 2009, an aseismic slip might occur beneath the Bungo Channel and southwest Shikoku. From September 2009 to January 2010, the slip area shifted toward southwest Shikoku. Since approximately March 2010, the slip has increased in magnitude and speed while expanding into the Bungo Channel. The estimated rupture process is similar to those of previous Bungo Channel slow slips, in that the slip starts in a shallower region and expands into a deeper region with the acceleration of the slip. The high-speed period of the 2010 event corresponds to a marked increase in the activity of low-frequency earthquakes, similar to that of the 2003 event. The total slip distribution of the 2010 event is similar to that of previous long-term Bungo slow slips, verifying the hypothesis that long-term slow slips are characteristic events in the Bungo Channel.