Soil amplification factors in terms of period derived from regressions using Costa Rican data set

摘要

Amplification factors for two soil types and 23 periods were obtained, using accelerographic records and their correlation with seismic parameters and local geology related to the site for Costa Rica. The factors were obtained from regressions between PSA (pseudo spectral acceleration) for 5% damping as the dependent variable and three independent variables: magnitude, hypocentral distance and soil type at each site, defined as S II (hard soil) and S III (medium to soft soil). It was assumed that the condition S I (rock) does not amplify seismic waves in the range of periods defined. Factors obtained for S II shows an almost constant value throughout the range of periods for the three different data sets considered (subduction, crustal or crustal + subduction combined) and compared with amplifications obtained by other authors, especially for Japan. For S III, amplification factors obtained in this investigation for the entire data set (subduction + crustal origin) are clearly higher than those proposed by other authors for Japan, mainlyabove period of 0.4 s.