[S-CG48] Science of slow earthquakes: Toward unified understandings of whole earthquake process

[SCG48-P32] Spatial distribution of slow slip events off the Boso peninsula from 1996 to 2018 under sparsity constraints

*Ryoko Nakata¹, Hideitsu Hino², Tatsu Kuwatani^3,4, Takahiro Akiyama⁵, Shoichi Yoshioka⁶, Masato Okada⁷, Takane Hori¹ (1.Japan Agency for Marine-Earth Science and Technology, 2.The Institute of Statistical Mathematics, 3.Department of Solid Earth Geochemistry, Japan Agency for Marine-Earth Science and Technology, 4.PRESTO, Japan Science and Technology Agency, 5.Graduate School of Science, Kobe University, 6.Research Center for Urban Safety and Security, Kobe University, 7.Graduate School of Frontier Sciences, The University of Tokyo)

We estimated spatial distribution of the six slow slip events (SSEs) off the Boso peninsula, central Japan, from 1996 to 2018. We have applied an inversion method called fused regularization, a type of sparsity constraint, suitable for detecting discontinuous changes in the model parameters, for evaluation function [Nakata et al., 2017]. In this study, to shorten calculation time, we used a type of approximation method by Obuchi and Kabashima [2016] to search hyperparameters, not LOO-CV (leave-one-out cross validation).

From our tentative results, the maximum slips for the 2002, 2011 and 2018 SSEs were large, and the 1996, 2007 and 2013 SSEs were small. The slip distributions of the 2011 and 2018 SSEs seem to be distributed southward than 2002. It is confirmed by numerical experiments that the difference in slip distribution is not due to GNSS station distribution.

Furthermore, we are conducting numerical simulation of earthquake generation cycles, which modelling SSEs off the Boso peninsula and M~8 earthquakes along the Sagami Trough. We will discuss slip distributions of SSEs and locked area during an interseismic period.