Slow Slip Interaction with Seismic Slow Earthquakes and Large Seismic Event

Abstract:

Past geodetic and seismic studies have revealed a diverse spectrum of fault slip behaviors including slow slip events (SSE), tremor, low frequency earthquakes (LFE) and very-low frequency earthquakes (VLFE). Despite their well observed nature, it remains enigmatic how SSEs interact with seismic slow earthquakes (tremor, LFEs, VLFEs) and large distant seismic event. GPS measured long-term SSEs have been occurring recurrently in southwest Japan since GEONET installation in 1996. Our investigation of the space-time relationship between these geodetically determined slow slip transients and seismically observed LFEs/tremor and VLFEs shows a universal modulation by up-dip slow slip on the downdip LFEs/tremor activities, and persistent spatial distribution, in which slip transients mainly concentrate on the transition zone from strong coupling region to downdip LFEs/tremor area and relieve elastic strain accumulation at transitional depth. For the 2009-2011 Bungo Channel SSE, we find a strong but distinct temporal correlation between transient slip and LFEs and VLFEs, suggesting different triggering mechanisms for slow slip to interact with these slow earthquake types. We also find the 2011 Tohoku-Oki earthquake disrupted the normal source evolution of this SSE, possibly due to large stress perturbation caused by the earthquake. Noticeably this earthquake also appears to change the behavior of subsequent SSEs with a new event occurred in late 2014 at roughly the same source location but much shortened interval from the past event.