HR: 09:45h
AN: S41C-07    [Abstracts]
TI: Spectral Element Modeling of 3D Site Effects in the Alpine Valley of Grenoble, France.
AU: * Chaljub, E
EM: Emmanuel.Chaljub@obs.ujf-grenoble.fr
AF: LGIT Grenoble, France., 1381, rue de la piscine. BP 53., Grenoble, 38041 France
AU: Cornou, C
EM: Cecile.Cornou@obs.ujf-grenoble.fr
AF: LGIT Grenoble, France., 1381, rue de la piscine. BP 53., Grenoble, 38041 France
AU: Gueguen, P
EM: Philippe.Gueguen@obs.ujf-grenoble.fr
AF: LGIT Grenoble, France., 1381, rue de la piscine. BP 53., Grenoble, 38041 France
AU: Causse, M
EM: Matthieu.Causse@obs.ujf-grenoble.fr
AF: LGIT Grenoble, France., 1381, rue de la piscine. BP 53., Grenoble, 38041 France
AU: Komatitsch, D
EM: dimitri.komatitsch@univ-pau.fr
AF: Universit\'e de Pau et des pays de l'Adour, Avenue de l'Universit\'e, BP 576, , Pau, 64012 France
AB: Sitting on top of a 3D Y-shaped basin filled mostly with late quaternary deposits, the city of Grenoble (French Alps) is subject to strong amplification of seismic motion (see the SISMOVALP web site). In order to assess the magnitude and 3D complexity of these site effects, we propose a spectral element modeling approach previously applied to the prediction of strong ground motion in the Los Angeles sedimentary basin (Komatitstch et al., 2004). The spectral element method naturally accounts for depth variations of the free surface and of internal interfaces, such as the contact between the sediments and the bedrock. It is also well suited to model the propagation of surface waves generated at the basin edges. The 3D spectral element mesh honors the stiff surface topography of the mountains surrounding the city, as well as the bedrock depth obtained from extensive gravimetric measurements. In the basin, we use a generic 1D velocity model derived from geophysical measurements performed in a deep borehole that reached the substratum at 550 m depth in 1999. Results and comparison to data are shown in the time and frequency domain for small-size (Mw=2.5 and Mw=3.5) local events recorded in the past years. Then, a Mw=5.5 strike-slip event is simulated on the eastern border of the basin along the Belledonne fault, and the results are compared to those obtained by the method of Empirical Green Functions. References: http://www-lgit.obs.ujf-grenoble.fr/sismovalp/ Simulations of ground motion in the Los Angeles basin based upon the spectral- element method, Dimitri Komatitsch, Qinya Liu, Jeroen Tromp, Peter Sss, Christiane Stidham and John H. Shaw, Bulletin of the Seismological Society of America, vol. 94, p 187-206 (2004).
DE: 7260 Theory and modeling
DE: 7212 Earthquake ground motions and engineering
DE: 3210 Modeling
DE: 3230 Numerical solutions
DE: 0902 Computational methods, seismic
SC: Seismology [S]
MN: 2004 AGU Fall Meeting