2D SIMULATION IN THE GRENOBLE BASIN USING THE AKI-LARNER METHOD COMBINED WITH AN EQUIVALENT LINEAR APPROACH

ABSTRACT- In the framework of the ground motion simulation benchmark in the Grenoble basin, the two-dimensional response of the valley to SH waves is calculated by the discrete wave-number method proposed by Aki and Larner (Aki and Larner, 1970). To overcome the frequency upper bound limitation, the Aki and Larner’s method is combined with a one dimensional computation using a classical multi-layer method (Aki and Richards, 1980). The ground response is computed at ten receivers across the valley, nine at the surface, and one at depth. In the framework of the free style prediction of the benchmark, we use an original version of the method to assess the two-dimensional non-linear response of alluvial basins. The so-called “Aki-Larner extended method ” is associated to an iterative algorithm, as proposed by Seed and Idriss (1969) which accounts for the modulus and damping degradation using a linear visco-elastic model. Results in the linear and the equivalent linear cases are compared for the magnitude 6.0 earthquakes proposed in the framework of the benchmark