Numerical Analysis of Seismic Site Effects in Loess Region of Western China under Strong Earthquake Excitations

Tuo Chen,Qiyin Zhu,Yanhu Mu,Ping Wang,Zhijian Wu

doi:10.1155/2020/3918352

Abstract

The Loess Plateau is one of the most tectonically and seismically active areas in the world. Observations from past strong earthquakes, particularly the Minxian–Zhangxian and Wenchuan earthquakes, have shown distinctive evidence of seismic site effects in the mountainous area of southeastern Gansu province. In this study, seismic damage in the loess areas of southeastern Gansu province induced by these earthquakes was investigated and briefly described. Different types of ground motion were selected, and the one-dimensional equivalent linear method was used for numerical analysis of the ground motion effects in the loess regions. Moreover, seismic response analysis of a typical loess tableland was conducted. The results showed that the seismic responses of a typical loess tableland under different seismic excitations have totally different dynamic characteristics. Moreover, the seismic damage in loess regions was more serious under far-field seismic excitation compared with near-field seismic excitation with the same peak acceleration. Through this study, the quantitative assessment of ground motion effects can be approximately estimated and the mechanism of site amplification effects on ground motion is further explained.

Highlights

Loess and loessic deposits cover an area of 631,000 km2 of the mainland of China, which accounts for approximately 6.6% of the total area of the country. e Loess Plateau is located on the upper and middle stream of the Yellow River, covering an area of 440,000 km2 in the northwestern part of China
In addition to the theory of the reflection and refraction of seismic waves during the wave propagation, resonance theory may help explain the characteristics of the seismic response of loess tableland. e seismic response is strongest when the dominant frequency of the site is close to the dominant frequency of the strong motion
Based on the seismic damage investigation, different types of ground motions were selected considering the different earthquake characteristics. en, a seismic site response analysis was conducted; the seismic response of the loess tableland was investigated. e numerical results indicated that the mechanism of seismic response is very complex and that seismic damage can vary in the same area

Summary

Introduction

Loess and loessic deposits cover an area of 631,000 km of the mainland of China, which accounts for approximately 6.6% of the total area of the country. e Loess Plateau is located on the upper and middle stream of the Yellow River, covering an area of 440,000 km in the northwestern part of China. E Loess Plateau is located on the upper and middle stream of the Yellow River, covering an area of 440,000 km in the northwestern part of China. Observations from past earthquakes have shown distinctive evidence of seismic site effects in the mountainous area of the southeastern Gansu province. Wu et al [2] discussed the phenomena of site effects on ground motion in the mountainous area of southeastern Gansu province during the Wenchuan Ms8.0 earthquake. Wang et al [3] concluded that amplification of ground motion by loess deposits caused additional damage during the Minxian–Zhangxian Ms6.6 earthquake. During these two devastating earthquakes, the seismic site effects in the form of amplification or deamplification were quite obvious

Results

Discussion

Conclusion