Estimates of the site effects in Oaxaca, Mexico using horizontal to vertical spectral ratios

Abstract

We compare estimates of the site response in Oaxaca, Mexico determined using non reference-site spectral methods. In particular, the spectral ratio between horizontal and vertical components of the S-wave arrivals (e.g. Lermo and ChavezGarda, 1993) is used to estimate the site response of hard-rock and sediment sites. The results are compared with site functions determined by Castro et al. (1995) using a generalized inversion. Although the methods used are independent of a reference site, both provide similar site functions; and consistent amplification factors for the hard-rock sites. However, there is a scale discrepancy for the site on sediments which can be explained in part by the site constraint imposed in the inversion scheme.