Topographic Amplification of Seismic Motion: Observations and Simulations in 3D

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

This grant provides funding for the development of computational tools that will allow large-scale numerical simulations to be conducted to study the response of 2D and 3D convex and concave topographic features. Using these tools, a systematic parametric investigation will be performed to quantify the role of topogra­phic geometry, stratigraphy, soil nonlinearity and ground motion characteristics in site res­ponse. Numerical predictions will be validated via comparison with published field data from 3D arrays, speci­fically deployed to evaluate topographic ampli­fication effects. Numerical results and field observations will be finally compiled to develop simplified procedures for accounting of topography effects in engineering design practice. If successful, the results from this work will impact engineering design practices nationwide. While seismic hazard assessment and microzonation studies rely increasingly on wave motion simulations, most developments to date do not account for topographical features, making the sweeping assumption of a flat earth surface model. Observations from large earthquakes, however, have shown that the pre­sence of a strong topographic relief can significantly aggravate the catastrophic conse­quences of strong seismic motion. These effects of topography on site response may not be predicted by the widely employed flat surface models, and this work will lead to a next generation of wave motion simu­lation tools that take into account local topography. In addition, this work will contribute to the deve­lopment of design topographic amplification factors for generic features, to be implemented in excess of existing site amplification factors, and account for the topographic aggra­vation of ground motion.