Topographic effects evaluation for performance-based design

The evaluation of ground motion intensity measures is an important component of Performance-Based Earthquake Engineering (PBEE). Pronounced variations in ground motion can occur between level sites and areas with irregular surface topography such as ridges, canyons, or slopes. This paper presents the results of numerical analyses of slopes under seismic waves. The results show that these kinds of topographic irregularity may lead to intense amplification or de-amplification variability at neighboring points behind the crest of the slopes. Moreover, these analyses indicate that the amplification is highly frequency dependant and sensitive to the wave type and some measure of the topographic irregularity. There is no doubt that the presence of a slope plays a significant and important role in the spatial variation of the ground motion and therefore it is necessary to take this factor into account in the correct evaluation of the distribution of ground motion intensity measures (IMs).