HR: 1320h
AN: S43A-0990    [Abstracts]
TI: A method of prediction of strong ground motion by stochastic green function considering 3-D attenuation structure
AU: * Nakamura, R
EM: naka@tepsco.co.jp
AF: Tokyo Electric Power Services Co. Ltd., 3-3-3, Higasi-Ueno, Taito-ku, Tokyo, 110-0015 Japan
AB: The 3-D attenuation structure is a big problem to evaluate seismic ground motion when the seismic motion that uses a statistical Green function in the great earthquake such as Tonankai earthquake generated along subduction zone. On the other hand, Q structure analysis results (ex, Nakamura and Uetake,2004) of the short period beneath the Japanese Islands show strong inhomogeneity. Therefore, We developed the strong motion evaluation technique by a statistical Green function considering three dimensions Qs structure, and examined the effect of the 3-D Q structure using 1968 Tokachi-Oki earthquake fault parameter. First, we obtained 3-D Q structure of Hokkaido district in Japan by inversion using a large quantity data of the K-NET and the KiK-net strong ground motion records. Second, we modeled fault plane and its divided elements of the fault, and calculate ground motion using 3-D Q values between observation points and the elements, and summed calculated ground motion in time domain. The result of inversion shows that low-Q area are distributed widely on the north side of volcanic front, that distribute in Hokkaido from east to west. The checkerboard resolution shows no good in this area. It is thought that earthquake is very few in northern area in Hokkaido. Nakamura and Uetake (2004) reported there are strong Low-Q at only volcanic front area in Tohoku inland. They used same data and same inversion method. So, widely distributed Low-Q area obtained in Hokkaido district may distribute in smaller area actually than its calculated. So, we could not discuss detail of Q structure. Next, we tested calculation method in this study comparing two case of using 3-D attenuation structure and homoginious structure (here, Q=100f, f : frequency). The waveform synthesis technique of stochastic green function used Kamae et al (1991) method. The source acceleration spectrum and the envelope from the elements of fault were after Boore(1987). The spectrum gives 1-10Hz. Qs effect between calculation site and each divided elements of fault plane are differently considered in the 3-D case. The result of calculation of ground motion shows that the difference of amplitude between for near field site is very small, but the difference for far field site (x : about 100km) is large. And there is difference in ground motion in case of almost same hypocentral distance sites of far field.
DE: 7223 Seismic hazard assessment and prediction
DE: 7203 Body wave propagation
DE: 7212 Earthquake ground motions and engineering
SC: Seismology [S]
MN: 2004 AGU Fall Meeting