The State of the Art in Seismic Hazard Analysis

The seismic hazard analysis is concerned with getting an estimate of the strong-motion parameters at a site for the purpose of earthquake resistant design or seismic safety assessment. For generalized applications, seismic hazard analysis can also be used to prepare macro or micro zoning maps of an area by estimating the strong-motion parameters for a closely spaced grid of sites. Two basic methodologies used for the purpose are the “deterministic” and the “probabilistic” seismic hazard analysis (PSHA) approaches. In the deterministic approach, the strong-motion parameters are estimated for the maximum credible earthquake, assumed to occur at the closest possible distance from the site of interest, without considering the likelihood of its occurrence during a specified exposure period. On the other hand, the probabilistic approach integrates the effects of all the earthquakes expected to occur at different locations during a specified life period, with the associated uncertainties and randomness taken into account. The present paper gives a critical and detailed description of both deterministic and probabilistic approaches for seismic hazard analyses. A large number of example results are presented to illustrate the implementations of the two approaches. The results of the probabilistic approach are able to account for the effects of all the controlling factors in a balanced way, and can thus be considered more reliable. The advantages quoted in favour of using the deterministic approach can simply be achieved via deaggregation of the probabilistic hazard analysis.