Characterization of Heterogeneous Source Model of Intraslab Earthquakes Toward Strong Ground Motion Prediction

Since Japanese Islands are located along the subduction zone, large intraslab earthquakes that occurred within subducting slabs generated earthquake disaster (e.g., the 1993 Kushiro-oki earthquake, the 2001 Geiyo earthquake, and the 2003 Miyagi-oki earthquake). It is necessary to construct characterized source model for reliable strong motion prediction of intraslab earthquakes. Somerville et al. (1999) compiled the kinematic source models and proposed a set of empirical scaling relationships for inland crustal earthquakes. Murotani et al. (2008) proposed empirical scaling relationships for plate-boundary earthquakes. Mai and Beroza (2000) also studied scaling properties of kinematic source models. We started to compile kinematic source models of intraslab earthquakes to compare source scaling properties with those of inland crustal and subduction-zone plate-boundary earthquakes. At first, we characterized these heterogeneous slip distributions and extracted rupture area, asperity, and average slip following the procedure proposed by Somerville et al. (1999) to see general nature of source models for these intraslab earthquakes. We also collected SMGA (strong motion generation area, Miyake et al., 2003) source models by the studies on broadband strong ground motion simulation using the empirical Green's function method for intraslab earthquakes (e.g., Asano et al., 2003, 2004; Morikawa and Sasatani, 2004) to compare with the heterogeneous source slip models by waveform inversion. From the seven event source models (Mw 6.6- 7.7), the average size of total rupture area and combined area of asperities of intraslab earthquakes are 67% and 46% of those of crustal earthquakes under the same seismic moment. The ratio of the combined area of asperities to the total rupture area is 9-21% and it is almost the same for the crustal events. We also find that the stress drops on the asperity area shows 10-65MPa, which are larger than those of inland crustal earthquakes. The SMGAs coincide to the asperity area for the 2003 Miyagi-Oki, and the 2001 Geiyo earthquakes. The characterized source model for intraslab earthquakes will be discussed. Acknowledgments: This study is supported by the Special Project for Earthquake Disaster Mitigation in Metropolitan Tokyo Area of MEXT.