Contribution of the Long-term SSEs to Stress Accumulation Process in Southwestern Japan

Abstract:

I analyzed daily GNSS data and revealed the effect of SSEs on interplate coupling to reveal the overall temporal evolution of interplate states along the trough in southwestern Japan, especially the western part of the subduction zone, called the Nankai region. In this area, several SSEs were detected in 1997, 2003, and 2010.

The results show that the interplate coupling recovered quickly after the termination of the long-term SSEs, and it suggests a link between slow slips and great earthquakes. In this area, the interplate coupling fully recovered within several years after 1946 Nankai earthquake according to the results of Ito and Hashimoto (2004, JGR). Therefore, the recovery of the full coupling in the SSE patch is similar with the recovery of the interplate coupling in the Nankai area after 1946 Nankai earthquake, except for the complete difference of spatiotemporal scale.

I also examined the balance between stress accumulation and release in the region. Below the eastern part of the strongly coupled area, at a depth of ∼15 km, constant coupling of about 7 cm/yr takes place whether the SSE occurrs or not. In the center of the SSE region, at a depth of ∼25 km, about 40 % of the accumulated stress is released through SSEs at a maximum and the rest is still contributing to the stress accumulation process.