SIMULATION-BASED COMPARISON OF 4-SITE-RESPONSE ESTIMATION TECHNIQUES

Recent earthquakes have triggered renewed interest to understand bette r earthquake site response. Most of the studies comparing various tech niques for estimating site response were based on real data (from eart hquakes, nuclear blasts, and seismic noise). A theoretical approach, u sing synthetic data generated with the pseudospectral method, is used to compare four site-response estimation techniques. The limits of app licability of each method were determined by modeling microtremors and incoming SV waves (with different incidence angles) and analyzing the site amplifications. The first two techniques investigated consist of dividing the spectrum of the horizontal motion at a site by that of a reference site using either incident S waves or microtremors. The lat ter was unable to reveal either the resonant frequencies or peak ampli tudes in any cases. The two other techniques are based on the horizont al-to-vertical (H/V) spectral ratio using S waves or microtremors. The se techniques were found to reveal at least the fundamental resonant f requency and amplitude (former method only) within 10% error, in the c ase of simple geology (flat layers). However, the results show that th ese techniques are unable to take into account 2D effects such as focu sing effects and basin-edge effects and yield unreliable or incorrect results in such cases.