Modeling slow slip events and their interaction with large earthquakes along Hikurangi and Mexican subduction zones

Abstract:

Recent high-resolution geodetic observations revealed the occurrence of slow slip events (SSEs) along the various subduction plate interfaces. One of the fundamental questions is how slow slip events interact with large earthquakes. To investigate slow slip events and their interaction with large earthquakes, we model slow slip events and large earthquakes along the Mexican and Hikurangi subduction zones based on the model by Shibazaki and Shimamoto (2007).

Along the Hikurangi subduction zone, long-term SSEs (e.g., Manawatu SSEs) occur at deeper portions (25–60 km) and short-term SSEs occur along the shallow northern and central parts (e.g., Wallace et al., 2012). We reproduce the long-term Manawatu SSEs and short-term shallow SSEs by setting the effective stress of these zones at around 3.0 MPa and 0.6 MPa, respectively. The effective stress of the Manawatu SSE zone is approximately five times larger than that of the short-term SSE zones. However, the ratio of effective stress to critical displacement of the Manawatu SSE zone is smaller than that of the short-term SSE zones. We also investigate the interaction between the SSEs and large earthquakes. A large earthquake nucleates at the southern locked segment and propagates to the northern narrow seismic zones. Slips occur even at the SSE zones, and these slips contribute to the size of the earthquake.

In the Guerrero region, large SSEs of around Mw 7.5 occur every 3–4 years (Radiguet et al., 2012). We reproduced Guerrero long-term SSEs occurring at intervals of 4–5 years by setting the effective normal stress and the critical displacement at around 2.0 MPa and 4mm at the SSE zones. To reproduce large earthquakes, we consider segmentations of rupture areas in seismogenic zones. In many cases, large earthquakes near the SSE region initiates during occurrence of SSEs. In the present model, velocity strengthening occurs at higher velocities at the SSE zones; therefore, when earthquakes occur in the seismogenic zones, only small slips occur at the SSE zones and then, large afterslips can occur along the SSE zones.