Effects of topography

Effects of Realistic Surface Topography on Seismic Ground Motion in the Yangminshan Region of Taiwan Based upon the Spectral-Element Method and LiDAR DTM. (April 2009)

In general, topographyincreases the amplitude of shaking at mountains tops and ridges, whereas valleys usually have reduced ground motion, as has been observed in both records from past earthquakes and numerical simulations.However, the effects of realistic topography on ground motion have not been clearly characterized in numerical simulations, especially the seismic response of the true ground surface.
Numericalsimulations show that seismic shaking in mountainous areas is strongly affected by topography and source frequency domain. The amplification of ground motion mainly occurs at the tops of hills and ridgeswhilst the valleys and flat-topped hills experience lower levels of ground shaking,
We demonstrate that topographic variations can change peak ground acceleration (PGA) values by +/- 50% inmountainous areas, and the relative change in PGA between a valley and a ridge can be as high as a factor of 2 compared to a flat surface response. This suggests that high resolution, realistic topographicfeatures should be taken into account in seismic hazard analysis, especially for densely populated mountainous areas.

Several numerical studies have indicated that structures located at the tops ofhills, ridges, and canyons suffer more intense damage than structures situated at the base of hills.
Boore – 1972 “A note on the effect of simple topography on seismic SH waves” BSSA 62 275-284
Geli –1988 “The effect of topography on earthquake ground motion: a review and new result” BSSA 78 42-63
Scott – 1997 “Topography effects on the seismic response of steep slopes” BSSA 87 701-709
Ma – 2007“Effects of large scale surface topography on ground motion, as demonstrated by a study of the San Gabriel Mountains, Los Angeles, California” BSSA 97 2066-2079

Lee, Chen, Liu (2008) used the...