Abstract
AbstractWe estimated strong motion generation area (SMGA) source model which is responsible for broadband (0.2, 0.3–10 Hz) strong motions of the 2005 west off Fukuoka prefecture earthquake and its largest aftershock using the empirical Green’s function (EGF) method. The estimated SMGAs are almost corresponding to the large slip area deduced by kinematic waveform inversion. The SMGA rupture for the mainshock propagated mainly upward and toward the northwest with rupture velocity of 3.15 km/s. The size of the SMGA follows the self-similar empirical formula of the asperity size derived by Somervilleet al.(1999). The stress drop of the mainshock SMGA is calculated to be 10.7 MPa, which is larger than those of the largest aftershock SMGA and the aftershocks used as EGF.
Highlights
At 10:53 on 20 March 2005, an MJ 7.0 earthquake occurred in the off-shore of the Fukuoka prefecture, northern Kyushu island, Japan
We estimated strong motion generation area (SMGA) source model which is responsible for broadband (0.2, 0.3–10 Hz) strong motions of the 2005 west off Fukuoka prefecture earthquake and its largest aftershock using the empirical Green’s function (EGF) method
In order to investigate the source characteristics that are responsible for strong motions up to higher frequency, we estimated the strong motion generation area (SMGA, Miyake et al, 2003) from broadband (0.2–10 Hz) strong motion simulation using the EGF method proposed by Irikura (1986)
Summary
At 10:53 on 20 March 2005, an MJ 7.0 (magnitude determined by Japan Meteorological Agency, JMA) earthquake occurred in the off-shore of the Fukuoka prefecture, northern Kyushu island, Japan. SMGA is a rectangular area with no explicit heterogeneities of slip, stress drop and rupture velocity inside it (Miyake et al, 2003) This simple source model has successfully been applied to explain broadband ground motions of many large to moderate-sized earthquakes. The SMGA was assumed to be located on the fault plane estimated by F-net moment tensor solution and the rupture starting point of the mainshock was assumed as the hypocenter determined by Institute of Seismology and Volcanology, Kyushu University. These fault plane and hypocenter are the same as those used in the kinematic source inversion by Asano and Iwata (2006). Seismic moment of the SMGA is calculated from multiplying that of the EGF event by the flat level of the spectral ratio, C N 3
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