The Effect of Opak Fault on Liquefaction Potential at Toll Road Construction in Klaten Regency, Central Java

Abstract

The activity of the Opak Fault on May 27th, 2006, caused a strong earthquake of Mw 6.3, then known as the Yogyakarta Earthquake. Previous studies have shown that several damages during the earthquake were caused by liquefaction. This paper aims to determine potential liquefaction hazards at toll road construction in Klaten Regency, within less than 10 km of the Opak Fault. The liquefaction potential was analyzed from Standard Penetration data using the simplified procedure to determine the safety factor and Liquefaction Potential Index by Iwasaki et al. (1981). In addition, vertical displacement caused by liquefied soil was calculated using the equation developed by Yoshimine et al. (2006). Based on the analysis of the liquefaction potential of 10 boreholes, the results showed that liquefaction occurs at 6 boreholes, with a high to a very high level of liquefaction potential index with a maximum horizontal acceleration of at least 0.46g. The extensive ground surface damage potentially occurs at 2 boreholes, with the vertical settlement of 32.55 cm and 47.02 cm, which occur at the nearest site distance to Opak Fault.