Two-dimensional simulation of the seismic response of the Santiago Basin, Chile

Results from an ambient noise tomography, gravimetric studies, and local geophysical surveys are combined to develop three representative cross-sections of the Santiago Basin, Chile, that include the main geological features and the wave velocities of the materials. One-dimensional (1D) and two-dimensional (2D) seismic responses were simulated for each cross-section, considering input seismic signals polarized in different directions. Amplification factors calculated in the surface of the cross-sections highlight the larger amplitudes and durations of the strong-ground motions in the softer deposits of the Basin due to surface waves generated at the boundaries of the rock outcrops. 2D over 1D aggravation factors for several earthquake ground motion characteristics indicate that 2D effects are negligible in the stiff gravel deposits and that the 1D simulations cannot capture the basin edge effects in the fine-grained soils. Numerical predictions are confirmed using the analyses of earthquake records of the 2015 Mw 8.3 Illapel Earthquake.