In this paper the free-field response at the Large-Scale Seismic Test (LSST) site in Lotung, Taiwan, during the earthquake of May 1986 is studied, comparing the downhole motions recorded in-situ with the results of simple equivalent-linear visco-elastic analyses and advanced finite element numerical simulations. The comparison between recorded array data and numerical predictions obtained with approaches of different level of complexity allows to highlight the limits and benefits of the adopted numerical schemes and to assess the performance of the advanced non-linear approach with respect to the traditional equivalent-linear model.