[SCG52-P05] Spatial distribution and b-values of earthquakes beneath Kii Peninsula, southwestern Japan
Keywords:intraslab earthquake, b-value, tremor, Oceanic mantle, Acoustic emission, Kumano acid rocks
Experimental results of the acoustic emissions (Ferrand et al. 2017; Kita and Ferrand, under review) indicated that the b-value of peridotite rocks increases with increase of hydration. Therefore, the oceanic mantle beneath southwestern Kii peninsula is more serpentinized than that beneath northeastern Kii peninsula. On the other hand, the mantle wedge beneath southwestern Kii peninsula is less serpentinized than that beneath northeastern Kii peninsula, which is consistent with the low attenuation structure of the mantle wedge there by Kita and Shibutani (2017). Theoretical simulation study for propagation of episodic tremor and slip by Ando et al. (2012) show that segmentations of slow-slip propagation (in the strike direction of the plate interfaces) occur depending on heterogeneous distribution of rheological strength on plate interfaces. The edges of the segments of slow slip correspond to points at which the rheological properties change and the spatial distribution of the seismic attentuation structure. As indicated by Kita and Matsubara (2016) beneath Shikoku region based on the atteuation structure imaging, the heterogeneity condition of the overlying plate and subducting plate could cause a formation of a segment of ETS.