Seismic Wave Propagation in South America (original) (raw)

below the oceanic trench off the coast from Iquique. For the model of the structure below the oceanic trench off the coast of Iquique, the modes of the shorter periods travel practically entirely in the sediments in the trench (assumed to be of thickness 1 km), while the mode of period 10 is travels predominantly in the low velocity zone at a depth of approximately 110 km. The phase velocities of these modes in the model of the structure below Iquique are between 3.06 and 4.14 km/s; the phase velocities of the Love modes of shorter period (1.9 s to 3.7 s) in the model of the structure below the trench are between 0.51 s and 0.57 s. There is practically no coupling between the Love modes below the oceanic trench and the modes below Iquique. At present we are considering the relation between the Love and Rayleigh modes of short period in our various models and the L9 and the R. phases. For Colombia, we have constructed models of the regions below Quibd6, below Barranquilla and below the Caribbean Sea northwest of Barranquilla. The Caribe plate motion near M~rida, western Venezuela, suggests, together with right hand strike-slip motion, a substantial portion of thrust. We are at present analyzing by the finite element method the propagation of Love and Rayleigh waves across these regions.