Liquefaction macrophenomena in the great Wenchuan earthquake

Chen Longwei¹, Yuan Xiaoming¹, Cao Zhenzhong¹, Hou Longqing², Sun Rui1, Dong Lin¹,
Wang Weiming¹, Meng Fanchao¹ and Chen Hongjuan¹

1. Institute of Engineering Mechanics, China Earthquake Administration, Harbin 150080, China
2. East China Institute of Technology, Fuzhou 344000, China

Abstract: On May 12, 2008 at 14:28, a catastrophic magnitude Ms 8.0 earthquake struck the Sichuan Province of China.
The epicenter was located at Wenchuan (31.00oN, 103.40oE). Liquefaction macrophenomena and corresponding destruction
was observed throughout a vast area of 500 km long and 200 km wide following the earthquake. This paper illustrates the
geographic distribution of the liquefaction and the relationship between liquefaction behavior and seismic intensity, and
summarizes the liquefaction macrophenomena, including sandboils and waterspouts, ground subsidence, ground fissures
etc., and relevant liquefaction features. A brief summary of the structural damage caused by liquefaction is presented
and discussed. Based on comparisons with liquefaction phenomena observed in the 1976 Tangshan and 1975 Haicheng
earthquakes, preliminary analyses were performed, which revealed some new features of liquefaction behavior and associated
issues arising from this event. The site investigation indicated that the spatial non-uniformity of liquefaction distribution was
obvious and most of the liquefied sites were located in regions of seismic intensity VIII. However, liquefaction phenomena
at ten different sites in regions of seismic intensity VI were also observed for the first time in China mainland. Sandboils and
waterspouts ranged from centimeters to tens of meters, with most between 1 m to 3 m. Dramatically high water/sand ejections,
e.g., more than 10 m, were observed at four different sites. The sand ejections included silty sand, fine sand, medium sand,
course sand and gravel, but the ejected sand amount was less than that in the 1976 Tangshan earthquake. Possible liquefaction
of natural gravel soils was observed for the first time in China mainland.

Keywords: Wenchuan earthquake; post-earthquake investigation; liquefaction; macrophenomena



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