Seismic site effects in a deep alluvial basin: numerical analysis by the boundary element method

Jean-François Semblat (1) , Anne-Marie Duval (2) , Patrick Dangla (3)

1 LCPC/MSRGI - Division Mécanique des Sols des Roches et de la Géologie de l'Ingénieur
2 ERA 6 Risque sismique - Equipe recherche associée au LCPC - ERA 6 Risque sismique
3 LMSGC - Laboratoire des matériaux et structures du génie civil

The main purpose of the paper is the numerical analysis of seismic site effects in Caracas (Venezuela). The analysis is performed considering the boundary element method in the frequency domain. A numerical model including a part of the local topography is considered, it involves a deep alluvial deposit on an elastic bedrock. The amplification of seismic motion (SH-waves, weak motion) is analyzed in terms of level, occurring frequency and location. In this specific site of Caracas, the amplification factor is found to reach a maximum value of 25. Site effects occur in the thickest part of the basin for low frequencies (below 1.0 Hz) and in two intermediate thinner areas for frequencies above 1.0 Hz. The influence of both incidence and shear wave velocities is also investigated. A comparison with microtremor recordings is presented afterwards. The results of both numerical and experimental approaches are in good agreement in terms of fundamental frequencies in the deepest part of the basin. The boundary element method appears to be a reliable and efficient approach for the analysis of seismic site effects.

Mots clés: seismic waves; site effects; amplification; topography; caracas

Domaines: Mécanique des structures [physics.class-ph]; Mécanique des structures [physics.class-ph]

Jean-François Semblat, Anne-Marie Duval, Patrick Dangla. Seismic site effects in a deep alluvial basin: numerical analysis by the boundary element method. Computers and Geotechnics, 2002, 29 (7), pp.573-585. ⟨10.1016/S0266-352X(02)00017-4⟩. ⟨hal-00355605⟩