Assessment of seismic liquefaction hazard in Shanghai based on ground motion intensity and Standard Penetration Test

Abstract

Shanghai is located in the alluvial plain of the Yangtze River Delta, the merge area of the Huangpu River and Suzhou River. The unique geographical and sedimentary environment have formed the shallow sand layers in Shanghai. Due to the significant urbanization process in Shanghai, geological hazard analysis, particularly the assessment for seismic liquefaction hazard in the Shanghai urban area has become an subject to be studied urgently. In this paper, we presented a regional liquefaction hazard analysis model. Based on the borehole Standard Penetration Test (SPT) data and regional Peak Ground Acceleration (PGA) zonation of the Shanghai area, we analyzed liquefaction risks with different probability of exceedance in 50 years. As our results indicated, under the condition that earthquake with 10% probability of exceedance in 50 years happens, more than 66.0% of the land area in Shanghai will not be affected by earthquake-induced liquefaction, 21.8% will only surfer modest liquefaction, and only 12.3% has the risks of serious liquefaction. These places cover Chongming island, Hengsha island, Changxing island and the banks of the Huangpujiang River and the Suzhou River. Provided that earthquake with 2% probability of exceedance in 50 years happens, due to the overall increase of peak ground motion acceleration, not less than 46.25% of the land area may suffer from modest to serious liquefaction risks. Although the rare seismic liquefaction risks exist, the probability of that is quite low. The current high fortification intensity for Shanghai in Chinese Code for Seismic Design of Building may result in unnecessary cost of construction. Our study provides new ideas and suggestions for perfecting the Code for Seismic Design of Building for Shanghai.

Keywords

• seismic liquefaction
• ground motion
• standard penetration test
• assessment for liquefaction hazard