Earth Planets Space, Vol. 60 (No. 10), pp. 1023-1028, 2008LETTER
Central Research Institute of Electric Power Industry, 1646 Abiko, Abiko-shi, Chiba 270-1194, Japan
(Received July 2, 2007; Revised May 8, 2008; Accepted July 1, 2008; Online published November 7, 2008)
The source rupture process during the 2007 Noto Hanto earthquake is inferred using a broadband waveform inversion technique based on the empirical Green's function and the simulated annealing. The spatio-temporal distributions of the moment density and rise time on the fault are estimated from displacement motions in the frequency range from 0.1 to 2 Hz, and effective stress distribution is derived from the velocity motions in the frequency range up to 5 Hz. Results from the displacement inversion indicate that the seismic moment is mainly released from a single asperity with an area of 10 × 10 km2, and total moment release is estimated to be about 1.3 × 1019 N m. The velocity inversion shows that the high effective stress area distributes on and around the asperity, in particular at the deep periphery of it. The broadband strong motions determined using the conventional source model composed of only the moment distribution are compared with those calculated by considering both moment and effective stress separately. The fit between observed acceleration motions and synthetic ones from both source models are generally good in the frequency range up to 10 Hz, and no evident difference is recognized.
Key words: Rupture process, waveform inversion, strong ground motion, simulated annealing, empirical Green's function.