Investigation of small earthquakes and microseismicity at the down-dip end of the seismogenic zone associated with slow slip events and large subduction earthquakes

Abstract:

The region between the occurrence of slow slip events (SSEs) and large to great earthquakes has proven to be difficult to classify, particularly because the region is often located offshore and ocean bottom seismometer networks are sparse. It is a common observation that small earthquakes and microseismicity occur at the down-dip end of the seismogenic zone, such that the termination of this seismicity has been used as a potential indicator of the extent of future large to great earthquakes. Observations from the recent M_w 9.0 March 11, 2011 Tohoku-Oki and M_w 7.4 March 20, 2012 Ometepec earthquakes also indicate that small earthquakes and microseismicity at the down-dip end of the seismogenic zone occurred coincident with SSEs in the time period that led up to the large earthquakes. For this study we employ the earthquake simulator, RSQSim, to better understand the physical conditions necessary to produce small earthquakes and microseimicity at the down-dip end of the seismogenic zone similar to what has been observed. Additionally we seek to better understand the relationship between the small earthquakes and microseismicity, SSEs, and large earthquakes. Physical conditions to be explored include the effective normal stress, frictional properties, and slip speed, and the spatial distribution of these parameters necessary to reproduce the observations.