Originality and relevance

The importance of long period motions on the response of large-scale structures (such as high-rise buildings, fluid-storage tanks, suspension bridges, etc.) has been well recognized by the earthquake engineering community. However, because such long period motions are usually associated with surface waves, their incorporation in analysis procedures was never systematically performed (to the best knowledge of the members of this consortium).

Part of the problem was the fact that surface waves are described by more complicated characteristics (e.g. dispersion) that may not be well understood widely among earthquake engineers. Furthermore, selection of strong motion records containing surface waves with particular characteristics (e.g. Rayleigh waves vs. Love waves) is not a trivial process. Also, techniques to synthesize strong motion records that contain surface waves with particular characteristics, are not widely available (if they exist at all).

In the last four decades great progress has been made in modeling and predicting strong ground motion. In particular, great strides have been accomplished in stochastic modeling of strong ground motion and in particular, of body waves. Unfortunately, the same statement cannot be made for basin-induced surface waves which are almost always present in the recordings obtained on the floor of sedimentary basins. Although numerous investigators have used a variety of numerical techniques to simulate basin-induced surface waves, no simple ‘guidelines’ have been developed as to how to use the stochastic modeling technique, mentioned above, to incorporate in the modeling/simulation process the basin-induced surface waves.