Seismic hazard prediction using multispectral amplification maps in a complex topographic area: A case study of Qiaozhuang town, Sichuan Province, Southwest China

Abstract

Earthquakes can cause widely distributed slope failures and damage in mountainous areas. The accurate prediction of ground motions in mountainous areas is essential for managing the seismic risk of urban cities near mountains but is restricted primarily by complex seismic site amplification effects in areas of uneven terrain. This study selected Qiaozhuang town located in the Qingchuan—Pingwu fault zone, Southwest China, as a case study. A simulator for mapped seismic responses using a hybrid model (SiSeRHMap) was applied to compute the multispectral seismic topographic amplification maps at the three slope units surrounding Qiaozhuang town (Weigan hill, Mt. Dong, and Mt. Shizi). Post-earthquake damage survey maps, 1D seismic site response spectral ratios, and H/V spectral ratios of earthquake data were used to validate the computed seismic site amplification factors and resonance frequencies. The results suggest that strong topographic amplification effects usually occur at distinct slope locations, such as hilltops, convex slope positions, upslope, and narrow ridges. The computed topographic amplification factors in the study area reached up to 2.4 at upslope or hilltops, and the resonance frequencies were between 3 and 10 Hz. Topographic effects can be as important as stratigraphic effects when assessing seismic amplification effects in the study area. We conclude that both topographic and stratigraphic effects should be considered in the comprehensive seismic hazard assessment of the study area or other similar mountain towns.