Deep slow-slip events promote seismicity in northeastern Japan megathrust
M. Khoshmanesh, Manoochehr Shirzaei, Naoki Uchida
Abstract
The sliding movement between oceanic and crustal plates in subduction zones is accommodated through both earthquakes and quasi-static or transient aseismic slip. On northeastern Japan megathrust, aseismic transients, known as slow-slip events, are suggested to precede and trigger major earthquakes in their immediate surroundings. However, the geodetic evidence for these episodic slow-slip events, as well as their link to the seismicity on neighboring locked segments of the megathrust, is missing. Here, we combine the on-shore geodetic data set with seismic observations during the interseismic period of 1996–2003 and demonstrate that episodic slow-slip events are prevalent across the down-dip portion (∼30–70 km depth) of the megathrust and the associated stress changes modulate the seismicity rate on the neighboring seismogenic zone. Consequently, small- to moderate-size earthquakes are periodically triggered, whose interaction through a domino effect might occasionally lead to major earthquakes. This observation has a profound impact on the estimation of seismic hazard in the region, introducing a new triggering mechanism that acts across the megathrust to the extent that has not been acknowledged before.