S31A-2713
Modeling long- and short-term slow slip events and their interaction with large earthquakes along the Hikurangi subduction zone
Wednesday, 16 December 2015
Poster Hall (Moscone South)
Bunichiro Shibazaki, International Institute of Seismology and Earthquake Engineering, BRI, Tsukuba, Japan, Takanori Matsuzawa, National Research Institute for Earth Science and Disaster Prevention, Tsukuba, Japan, Laura M Wallace, University of Texas at Austin, Institute for Geophysics, Austin, TX, United States and Yoshihiro Ito, Disaster Prevention Research Institute, Kyoto University, Kyoto, Japan
Abstract:
Recent high-resolution geodetic observations revealed the occurrence of various slow slip events (SSEs) along the Hikurangi subduction plate interfaces. Long-term SSEs with a duration of 1.5 years (e.g., Manawatu SSEs) occur at the deeper portion of the Hikurangi subduction zone, and shallow short-term SSEs with a duration of 1–3 weeks occur along the northern and central parts of the subduction zone. Wallace et al. (2012) reported a sequence of simultaneous short-term and long-term SSEs along the Hikurangi subduction zone during 2010–2011. In the present study, we perform quasi-dynamic modeling on short-term and long-term SSEs along the Hikurangi subduction zone using a rate- and state-dependent friction law, while assigning realistic configurations of the plate interface. Based on the study of interseismic coupling by Wallace et al. (2009), we set the seismogenic zone where a-b is negative. We reproduce the long-term Manawatu SSEs and short-term shallow SSEs by setting the effective stress of these zones at 2.56 MPa and 0.48–0.64 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. A sequence of simultaneous short-term SSEs and the long-term Manawatu SSE can be reproduced as observed by Wallace et al. (2012). Long-term SSEs often trigger short-term SSEs that are located at the shallower extension of the Manawatu SSE zone. We also investigate the interaction between the SSEs and large earthquakes. A large earthquake nucleates at the southern 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. The occurrence of the various slip processes suggests heterogeneous distributions of constitutive law parameters along the Hikurangi subduction zone.
