New approach for coupling k−2 and empirical Green's functions: application to the blind prediction of broad-band ground motion in the Grenoble basin

• Published in: Geophysical journal international 2009, Vol.179 (3), p.1627-1644
• Main Authors: Causse, Mathieu, Chaljub, Emmanuel, Cotton, Fabrice, Cornou, Cécile, Bard, Pierre-Yves
• Format: Article
• Language: English
• Subjects: Sciences of the Universe
• ISSN: 0956-540X; 1365-246X
• DOI: 10.1111/j.1365-246X.2009.04354

We present a new approach for performing broad-band ground motion time histories (0.1–30 Hz) of a future earthquake in a sedimentary basin. Synthetics are computed with an hybrid scheme combining reciprocity-based 3-D-spectral element method simulations at low frequencies and empirical Green's functions (EGF) at high frequencies. The combination between both deterministic and empirical parts results in a set of hybrid Green's functions, summed according to a new k−2 kinematic model algorithm. The summation technique enables to remove the high-frequency artefacts that appear above the EGF corner frequency. The ground motion variability is assessed by generating a variety of source parameter sets selected from a priori probability density functions. This leads to a population of response spectra, from which the median spectral acceleration and standard deviation values are derived. The method is applied to simulate a MW 5.5 event in the deep Grenoble basin (French Alps). The comparison with EC8 regulations suggests the need of specific design spectra in the Grenoble valley.