This paper presents the first results of 3D simulations of the seismic response in the Caracas basin using the spectral element method. The seismic response of the basin is obtained by the excitation of an incident plane wave which is efficiently implemented via its traction and velocity at the rock sediments interface. A generalized filtering perfectly matched layer allows for a better absorption of surface waves in elongated basins. Our simulations clearly show combined effects from the topography and the basin, with diffracted waves coming from the mountains, and low frequency energy trapped in the deepest part of the basin. Spectral ratio exhibits focalization and 3D amplification effects.