Estimation of strong motion generation area (SMGA) based on the empirical Green's function
Speaker: Shih-Wei Yang
Abstract
The empirical Green's function (EGF) method, which uses actual small-event ground motions as the Green's functions instead of the theoretical Green's functions. If the two earthquakes follow the £s ? 2 source spectral model (Aki, 1967; Brune, 1970) with a different stress drop whose ratio is C , then N and C are related to the two flat levels of the spectral ratio of the large earthquake to the small earthquake records. Irikura et al. defined the ¡§strong motion generation area¡¨ as the area characterized by a large uniform slip velocity within the total rupture area, which reproduces near-source strong ground motions up to 10 Hz. The strong motion generation area of each mainshock is estimated by waveform fitting based on the empirical Green's function method. The low-frequency limit is constrained by the signal to noise level ratio of the small event record used as an empirical Green's function. Suzuki et al. analysized the 2005 west off Fukuoka prefecture earthquake. They got that the stress drop of strong motion generation area (SMGA) of the mainshock is 10.7MPa with the seismic moment 7.2 ¡Ñ 10 18 Nm. The length of SMGA is 4.1km, and the width is 10.2km. Also the stress drop of the lagest aftershock is 1.4Mpa. The length of SMGA is 4.0km, and the width is 4.5km. Another case is 2004 Mid Niigata Prefecture earthquake. Kamae et al. estimated the source model composed of two asperities. The length of the Asp1 is 7.5km, and the width is 10.0km; the length of the Asp2 is 4.0km, and the width is 4km. In this case, they pointed out the importance of the quantitative analysis of nonlinearity of the sedimentary soils at K-NET station.
Reference
Kamae,K., T. Ikeda, and S. Miwa, Source model composed of asperities for the 2004 Mid Niigata Prefecture, Japan, earthquake (M JMA =6.8) by the forward modeling using the empirical Green's function method, Earth Planets Space , 57, 533-538, 2005.
Suzuki, W. and T. Iwata, Source model of the 2005 west off Fukuoka prefecture earthquake estimated from the empirical Green's function simulation of broadband strong motions, Earth Planets Space , 58, 99¡V104, 200.