[S-CG45] Science of slow-to-fast earthquakes

[SCG45-P50] Influence of the 2011 Mw 9.1 Tohoku earthquake stress perturbation on Boso slow slip events

*Luhong Lu^1,2, Satoshi Ide², Yajing Liu¹ (1.McGill University, 2.University of Tokyo)

Keywords:slow slip events, earthquake cycle modeling, numerical simulation

Slow slip events (SSEs) are quasi-static fault slip on average several mm to cm accumulated in a few days to months in the vicinity of the subduction zone megathrust earthquake rupture patch. The spatiotemporal correlation between the slow and fast slip modes in some subduction zones such as Mexico and Costa Rica suggests possible interactions between them through stress transfer. We aim to model the impact of the 2011 Mw 9.1 Tohoku earthquake on the Boso SSEs to verify whether the change of recurrence interval is related to the stress transfer from the coseismic slip and afterslip, or there are undetected small Boso SSEs. GPS studies suggest that after the Tohoku earthquake, the recurrence interval of Boso SSEs dropped from 6 years in 1996 to 2 years in 2011 (Ozawa, 2014), followed by a recovery to 4.4 years by 2018 (Ozawa et al., 2019). Two small SSEs in 2005 and 2010 are suspected through a combined study of GPS and repeating earthquakes, indicating a shorter recurrence interval of Boso SSEs that is unaffected by the Tohoku earthquake (Gardonio et al., 2017). The Boso SSEs and the Tohoku earthquake will be simulated on non-planar fault models of the Philippine Sea plate and the Pacific plate through earthquake cycle modeling to understand the influence of earthquake stress perturbation on the recurrence interval of Boso SSEs. The model parameters will be optimized under the rate-and-state friction framework to reproduce the observed feature of SSEs, including the long-term recurrence interval, duration, magnitude, and slip rate. Simulations will be performed on multiple versions of the Philippine sea plate model to discuss the effect of plate geometry on the SSE slip distribution. Potential hidden SSEs with smaller magnitudes will be discussed from the modeling results to understand the SSE stress accumulation process and friction heterogeneity on the Philippine sea plate.



Gardonio, B., Marsan, D., Socquet, A., Bouchon, M., Jara, J., Sun, Q., ... & Campillo, M. (2018). Revisiting slow slip events occurrence in Boso Peninsula, Japan, combining GPS data and repeating earthquakes analysis. Journal of Geophysical Research: Solid Earth, 123(2), 1502-1515.

Ozawa, S. (2014), Shortening of recurrence interval of Boso slow slip events in Japan, Geophys. Res. Lett., 41, 2762–2768, doi:10.1002/2014GL060072

Ozawa, S., Yarai, H., & Kobayashi, T. (2019). Recovery of the recurrence interval of Boso slow slip events in Japan. Earth, Planets and Space, 71, 1-8.