Evaluation of Liquefaction in Karasu River Floodplain After the October 23, 2011, Van (Turkey) Earthquake

Abstract

The eastern shore of Lake Van was shaken by a powerful earthquake (M (w) 7.2) on October 23, 2011. The epicenter of the earthquake was located at about 30 km north of the Van Province, which is one of the main cities in the Eastern Anatolia. The Van Province and particularly its largest district Ercis were adversely affected by the earthquake, and unfortunately, a total of 600 people lost their lives. Besides severe constructional damages and building collapses, ground deformations were widespread at many locations nearby the Lake Van and Karasu River floodplain. Numerous sand boils and lateral spreading cracks were observed at the left and right embankments of the Karasu River, which is one of the major streams in the region. In this study, field observations on liquefaction and lateral spreading features triggered by the M (w) 7.2 Van earthquake are initially presented. Then, the results of subsurface investigations including trial pits, drillings and geophysical surveys on specific large-scale sand boils are explained. Subsequently, liquefaction back-analysis is performed considering the gathered subsurface data. The analysis indicates that the liquefaction occurred in a shallow zone with approximately 4 m thickness in the investigated area. The Liquefaction Potential Index method reveals high liquefaction potential for the analyzed sand boil location. In addition, the effect of cap soil thickness on liquefaction is once more validated by this case.