Site amplification and strong ground motion of the 2007 Noto Hanto, Japan, earthquake estimated from aftershock observation

Abstract

Abstract Site amplifications in the lowlands most affected by the 2007 Noto Hanto earthquake, Monzen, Anamizu, and Wajima, are examined using aftershock records observed at eight temporary seismic stations installed just after the mainshock and at two K-NET stations. The predominant frequencies of spectral ratios at alluvium sites in Anamizu and Wajima are approximately 1 Hz. Site amplifications at the alluvium sites are successfully reproduced from 1-D response analysis, except for that at ISK005 where 2-D or higher amplification effects are inferred to play a significant role. A source model composed of two asperities reproduces the ground motions of the mainshock using the empirical Green’s function method. The seismic moments of the asperities are 3.76×1018 N m and 2.21×1018 N m, respectively. Peak ground velocity (PGV) at alluvium sites during the mainshock are estimated to be 70–110 cm/s for Monzen, 50–110 cm/s for Anamizu, and 60–70 cm/s for Wajima.