Theme Lecture – Accounting for topography effects in seismic design
Surface topography features such as ridges, slopes and canyons can modify substantially the ground motion, as documented in several historic seismic events. This phenomenon has been extensively investigated in the literature by numerical, field and more recently experimental studies. Despite the plethora of studies, topography effects are either ignored or accounted for in a simplistic manner in existing design codes.
The lecture will demonstrate the interdependency of topographic and soil layer amplification, which is commonly ignored in design code provisions, both for unidirectional as well as bi-directional excitations. It will then propose a set of simple design equations for the estimation of topographic amplification in the vicinity of canyons, which account for the interdependency of topographic and soil layer amplification. It will be shown that the proposed equations can be readily used either in conjunction with existing design elastic response spectra, irrespective of the soil type, or to modify existing ground motion prediction equations within a probabilistic seismic hazard assessment.