Spatiotemporal evolution of aseismic interplate slip between 1996 and 1998 and between 2002 and 2004, in Bungo channel, southwest Japan

摘要: [1] Interplate aseismic slip in the Bungo channel area, southwest Japan, occurred during 1996–1998 and 2002–2004. We employed a square root information filter following time-dependent inversion technique to time series of daily coordinates global positioning system (GPS) sites. The results show that interplate beneath southwestern part Shikoku Island from late 1996, then shifted southwestward area May 1997 February 1998, subsided over with moment magnitude (Mw) 7.1. In contrast, 2002–2004 event shows an early stage March 2003 August 2003. From January 2004, expanded by around 30 km northeastward northern channel, decayed Mw reaching event, start expansion acceleration coincided occurrence short-term slow low-frequency earthquakes deep area. This is different spatiotemporal evolution despite having almost same similar magnitudes. A balance deficit forward on plate boundary suggests releases strain energy mainly episodic long-term events.