The nonlinear dynamic behavior of an alluvionar valley situated in São Sebastão region in Terceira island (Azores archipel) is performed. The Mohr-Coulomb model is used in this paper. A bidimensional cross-section with 1240 m long and 250 m depth is considered. The cross-section of the model is composed by layers having different type of ground, each one having their own geotechnical characteristics. The Distinct Element method is employed in this case. UDE Code is used. The size of Finite Elements has been tailored to the wavelength of the propagating waves through the layers. The objectives of this paper are: 1) The analysis of seismic response in terms of maximum values of shear strain at different spots along the depth; 2) The study of the influence of the lateral faults in the seismic response in terms of maximum values of shear strain and shear strain-stress relationship; 3) The analysis of the seismic response of the soils at different locations in terms of shear strain-stress relationship for “no fault” case. This is the first attempt to study the nonlinear behavior of this valley using a 2-D refined model. The UDEC code is used for studying, not only the nonlinear behavior of the soils, but also the influence of the faults to the seismic response of the soils
