LPI-Based Severity Mapping of Earthquake Induced Soil Liquefaction in Pacitan City Coastal Area Indonesia

Pacitan City, the capital of Pacitan Regency is located at the southern part of East Java Province. This area is facing directly to the earthquake source due to plates subduction between Indo-Australia and Eurasia plates. Southern part of this City is coastal resort area which is geologicaly consists of alluvial deposits that is still under compaction and some of the upper layers are consist of loose material. According to the condition, this area is vulnerable to the earthquake induced soil liquefaction. Five soil borings and 30 cone penetration tests were conducted in this study area to investigate soil properties for evaluating soil liquefaction. Severity of the potential surface damages due to liquefaction were identified by calculating Liquefaction Potential Index (LPI). The results show that study area is vulnerable to soil liquefaction, with potential damage severity vary from very low to very high. Medium to high severity of potential damage are distributed in almost area of the city, and only in the southern part close to the coast line have very high severity level.