Development of spatial correlation and coherency model for simulating tri-directional ground motion fields at the dam-foundation interface

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Structures and infrastructure with large footprints, including dams, are affected by spatially varying multi-component ground motions. The tri-directional ground motions at multiple supports or the ground motion fields at the dam-foundation interface can be simulated for given spatial coherency and tri-component response spectra specified at given probability level (i.e., seismic hazard). However, information on spatial coherency for tri-directional ground motions is unavailable. Moreover, the seismic hazard modeling is sensitive to the standard deviation and the (intra-event) spatial correlation of the residuals of the ground motion prediction equations (GMPEs), which are usually estimated based on records from a broad network of recording stations with a minimum distance between the stations more than about one kilometer. The application of the GMPEs together with their residuals derived using such records is adequate if the minimum distance between the supports of the infrastructure is similar to those of the records. However, one must investigate what are the most appropriate GMPEs, if the interest is focused on estimating the seismic hazards at multiple supports within a localized area, such as dam base. This proposal is to assess the probabilistic model of ground motion measures and seismic hazard that are applicable to a localized area, and to develop empirical spatial coherency model by considering multi-directional ground motions. For the analysis, the ground motion records from the dense arrays with short station-to-station distance will be employed. The developed probabilistic models of ground motion measures and the spatial coherency models are used as the basis for simulating tri-directional ground motions at multiple supports within a localized area or at the dam-foundation interface. The algorithm developed in this project is useful to assess seismic risk of dams, and could be integrated as part of HATCH's risk-based tools for evaluating dam safety and for prioritizing long-term safety maintenance program. The funding from NSERC for this project is to be used to support a post-doctoral fellow for six months.