Empirical Models for Surface- and Body-Wave Amplifications of Response Spectra in the Bogota Basin, Colombia

Empirical site amplification models for surface and body waves based on the average shear-wave velocity in the upper 30 m (V-S30) are developed for predicting horizontal response spectra in the Bogota basin, Colombia. By analyzing the earthquake ground-motion data recorded in Bogota, it is found that long-period ground motions with a period of 2 s from shallow earthquakes are strongly amplified within the basin, possibly as a result of the generation of surface waves at the basin edge, whereas shorter-period body waves with predominant periods between 0.5 and 1 s typically characterize records within the basin from deep earthquakes. The present results indicate that the attenuation relationship developed by Uchiyama and Midorikawa (2006) accurately reproduces the response spectra at reference rock sites. In this study, the site amplifications, defined as the ratio between the observed response spectrum and the reference spectrum obtained from the aforementioned attenuation relationship, are evaluated. Models of the site amplifications for surface and body waves are developed using the observed response spectra in Bogota and validated by comparing the model results to observation data from the 1999 Quindio, Colombia, and 2017 Chiapas, Mexico, earthquakes. The results confirm that the surface-wave amplification model developed in this study is shown to accurately reproduce the observed response spectra in Bogota.