Modeling short‐ and long‐term slow slip events in the seismic cycles of large subduction earthquakes

Abstract

Slow slip events (SSEs) occur in the deeper extents of areas where large interplate earthquakes are expected in subduction zones, such as the Nankai region of Japan and the Cascadia region of North America. In the Nankai region, SSEs are divided into long‐ and short‐term SSEs, depending on their duration and recurrence interval. We modeled and examined the occurrence of long‐ and short‐term SSEs and changes in their behavior during the seismic cycles of large interplate earthquakes. In these numerical simulations we adopted a rate‐ and state‐dependent friction law with cutoff velocities and assumed that the distribution of pore fluid controls the recurrence interval of both long‐ and short‐term SSEs. The recurrence intervals of reproduced short‐term SSEs decrease during a long‐term SSE, as observed in western Shikoku, in the Nankai region. The recurrence intervals of both types of SSEs become shorter in the later stages of interseismic periods. Large interplate earthquakes nucleate between the region where SSEs occur and the locked region of the large earthquakes, as suggested from observations of the 1944 Tonankai earthquake. Our numerical results suggest that the stress buildup process in a seismic cycle affects the recurrence behavior of SSEs.