Deep slow-slip events promote seismicity in northeastern Japan subduction zone

Mostafa Khoshmanesh, Manoochehr Shirzaei, & Naoki Uchida

Published August 12, 2019, SCEC Contribution #9433, 2019 SCEC Annual Meeting Poster #202

The sliding movement between oceanic and crustal plates in subduction zones is accommodated through both rapid stick-slip earthquakes and quasi-static or transient aseismic slip. On northeastern Japan subduction zone (NJSZ), 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 periodic slow-slip events as well as their link to the seismicity on neighboring locked segments of the megathrust is missing. Here, we combine the daily crustal deformation data set obtained from onshore global positioning system stations with creep observations from characteristically repeating earthquakes to model the spatiotemporal distribution of interseismic slip on NJSZ during period 1996-2003. The obtained result reveals a locked section in the central part and two creeping segments to the north and south, in the down-dip portion (~30-70 km depth) of the megathrust (Fig. 1B). We further demonstrate that episodic slow-slip events are prevalent across the northern deep creeping segment, and the associated stress changes modulate the seismicity rate on the neighboring seismogenic zone (Fig. 1C). Consequently, small- to moderate-size earthquakes are periodically triggered, whose interaction through a domino-effect occasionally leads to major earthquakes. This observation has a profound impact on the estimated seismic hazard in the region because it introduces a new triggering mechanism that acts across the megathrust on a range that was not known before.

Khoshmanesh, M., Shirzaei, M., & Uchida, N. (2019, 08). Deep slow-slip events promote seismicity in northeastern Japan subduction zone. Poster Presentation at 2019 SCEC Annual Meeting.

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