Japan Geoscience Union Meeting 2016

Presentation information

International Session (Oral)

Symbol S (Solid Earth Sciences) » S-CG Complex & General

[S-CG21] Recent advances and future directions in slow earthquake science

Sun. May 22, 2016 3:30 PM - 5:00 PM A08 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Yoshihiro Ito(Disaster Prevention Research Institute, Kyoto University), Michael Brudzinski(Miami University), Ryosuke Ando(Graduate School of Science, University of Tokyo), Hitoshi Hirose(Research Center for Urban Safety and Security, Kobe University), Amanda Thomas(University of Oregon), Chair:Ryosuke Ando(Graduate School of Science, University of Tokyo), Yoshihiro Ito(Disaster Prevention Research Institute, Kyoto University)

4:30 PM - 4:45 PM

[SCG21-23] Modeling long- and short-term slow-slip events and their interaction with large earthquakes along the Hikurangi subduction zone

*Bunichiro Shibazaki1, Laura Wallace2, Yoshihiro Ito3, Takanori Matsuzawa4 (1.International Institute of Seismology and Earthquake Engineering, Building Research Institute, 2.Institute for Geophysics, University of Texas at Austin, 3.Disaster Prevention Research Institute, Kyoto University, 4.National Research Institute for Earth Science and Disaster Prevention)

Keywords:Long- and short-term slow slip events, The Hikurangi subduction zone, Modeling, Large earthquakes

Recent geodetic observations revealed the occurrence of various slow slip events (SSEs) along the Hikurangi subduction plate interfaces (Wallace and Beavan, 2010). 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. One of the fundamental questions is how SSEs interact with large earthquakes. In the present study, we performed quasi-dynamic modeling on short-term and long-term SSEs and their interaction with large earthquakes along the Hikurangi subduction zone. We used a rate- and state-dependent friction law with a cut-off velocity to the evolution effect (Shibazaki and Shimamoto, 2007). We investigated a realistic configuration of the plate interface. On the basis of the study on interseismic coupling by Wallace and Beavan (2010), we set the seismogenic zone where a-b is negative. The long term average relative slip velocity of each element was fixed at 4.5 cm/year for simplicity.
We set both the Manawatu and Kapiti SSE regions at the deeper extension of the seismogenic zone. The activity of Kapiti SSEs changes significantly during a cycle of large earthquakes. When large earthquakes approach, slip velocities increase at the deeper extension of the seismogenic zone. Consequently, slip velocities of the Kapiti SSEs at the deeper extension of the seismogenic zone increase. During a large earthquake, coseismic slips occur at the Kapiti SSE zone, but the occurrence of SSEs is subsequently restrained for some time. We also developed a model which investigated subducting seamounts in the northern segment of the Hikurangi subduction zone. The effective stress is assumed to be very high in the region of seamounts. The seamounts act as barriers of slow slip but between seamounts slips propagate to the shallow fault zones. Comparison between our results and observations will be necessary to develop a more realistic model of SSEs in this region.