CONSIDERACIONES SOBRE AMPLIFICACIÓN SÍSMICA EN DEPÓSITOS ALUVIALES, CASO CUENCA DEL TEMPISQUE, COSTA RICA

Abstract

The study and analysis of seismic amplification was developed from the geologic setting of theTempisque Basin and other regions with similar geological settings (alluvial deposits considerate as soft soils).The first well group (northwestern of the basin) gave maximum acceleration’s amplitudes between 0,55-0,91 secfor an oscillation period of soil approximately of 0,88 and 0,71 sec. This area is where the biggest thicknessesof soft soil are located (between 35-60 m). The second group (central part) gave a period range for the maximumamplitude of 0,24-0,85 sec for an oscillation period approximate in 0,65 and 0,54 sec. The soft soil thicknessesare intermediate between 30-50 m. The third group (middle and southeastern part) present values of maximumamplitude in the range between 0,10-0,55 sec for an oscillation period of 0,23 and 0,14 sec. The thicknesses areminimum with values between 10-20 m. The spectral values of amplification in the rank considerated are 0,5-1,1g, 0,55-0,98g and 0,4-1,5g for the first, second and third well group respectively. For the third group theamplification factors trend to overestimate the maximum values of amplification for about 2g.The classification of soil types according to FEMA and ATC’s discernments was done in four types: B, C, D andE (rock, soft rock and very dense soil, soft soil, very soft soil).