Ground Response Analyses for a Zoned Earth Dam Site in Southern Italy

The evaluation of the performance of critical infrastructure such as earth dams is typically performed using site-specific input ground motions. Input motions can be defined to be consistent with target response spectra derived from probabilistic seismic hazard analyses (PSHA). Such analyses are based on site effects estimated by means of proxies derived from global databases. These site response estimates are called ergodic. The actual site-specific response (non-ergodic) will differ from the global average in a manner proportional to local site complexities. Seismic ground response analyses (GRA) can be used to quantify site-specific effects such as resonance, nonlinear behavior, and impedance. If non-ergodic approaches are used, uncertainties related to site effects can be reduced. In this paper, site-specific ground motions are selected to evaluate the seismic response of a zoned earth dam in southern Italy. Two different target spectra are used: The Uniform Hazard Spectrum (UHS) and the Conditional Spectrum (CS). Differences between these spectra and their effects on site-response are illustrated. Limitations of GRA are also discussed and amplification functions for the foundations of the dam are shown.