Space-time Renewal Model for Repeating Earthquakes and Slow Slip before and after the Major Earthquakes in the Northeastern Japan Subduction Zone

Abstract:

Repeating earthquake sequences on the plate subduction zone represent the slip-rate histories around their fault patches. So they are useful resources for monitoring precursory aseismic slip of major earthquakes on plate boundaries. Repeating earthquakes are often modeled by renewal processes, point processes whose recurrence intervals are independent and identically distributed. However, their repeating intervals are greatly influenced by larger seismic events or aseismic slow slip, and hence we need to model such non-stationary behavior of repeating earthquakes. In this study, we propose a non-stationary space-time model for repeating earthquakes based on the model in Nomura et al. (2014) applied to the Parkfield catalog. We used the empirical relation between magnitudes and slip sizes of repeating earthquakes by Nadeau and Johnson (1998) to estimate the slip-rate histories in repeating sequences. The proposed model can estimate spatio-temporal variation in slip rate with smoothness restriction adjusted to optimize its Bayesian likelihood.
We apply the proposed model to the large catalog of repeating earthquakes in Uchida and Matsuzawa (2013) on subduction zone of Pacific Plate in the northeastern Japan from 1993 to 2011 and estimate slip-rate history of the plate boundary. From this analysis, we discuss the characteristic changes in slip rate before and after the major earthquakes such as Sanriku-Haruka-Oki (1994 Mw7.6), Tokachi-Oki (2003 Mw8.0), Kushiro-Oki (2004 Mw7.1), Fukushima-Oki (2008 Mw6.9), Ibaraki-Oki (2008 Mw7.0) and Tohoku-Oki (2011 Mw9.0).