Amplification of thickness and topography of loess deposit on seismic ground motion and its seismic design methods

Abstract

The Loess Plateau in China is a region with the biggest thickness and most complicated topography of loess deposit in the world, where is affected by strong earthquakes frequently. The seismic amplification effects were discovered in the Plateau during the Wenchuan Ms8.0 earthquake and some other strong events. The field investigations, observations, and analyses indicated that large number of casualties and tremendous economic losses were caused not only by collapse and damage of houses with poor seismic performance, landslides, liquefaction and seismic subsidence, but also amplification effects of thickness and topography of loess deposit on seismic ground motion. In this paper, the characteristics of strong ground motion recorded in the region were analyzed; shaking table tests were performed and numerical analysis was carried out on amplification of thickness and slope of loess deposit on seismic ground motion. Moreover, we also developed site amplification factors of ground motion for seismic design of engineering projects on loess sites. The results showed that the amplification effects are more predominant with increase of thickness and slope of loess deposit. The ground motion may be amplified in seismic intensity by 1–2°, PGA by 1.1–2.2 times, and predominant period by 1.1–1.6 times respectively.