Overview of flowslide in Balaroa during liquefaction of the 2018 Palu earthquake

An earthquake with a magnitude of 7.5 occurred on September 28th, 2018, at 18:02 in Palu, Central Sulawesi. The Palu-Koro Fault experienced a strike-slip mechanism. The earthquake epicentre is located 72 km north of Palu, with an earthquake depth of 10 km. This earthquake triggered extensive and massive landslides in the Balaroa Village. The goal achieved through this research is to determine the potential for liquefaction in the area affected by the liquefaction of Balaroa using the geoelectric method. This type of research uses a survey method. The contour map shows that the initial slope between the crown and toe is estimated to be about 3°. Based on the grain distribution graph plotted into the Tsuchida curve (1970), it is obtained that the soil in the sample contains predominantly sand and has a grain size that is within the boundaries of the potential liquefaction zone. Analysis of the Factor of Safety shows that the average liquefaction potential occurs at a depth of 6.5 meters. Liquefaction potential is strongly influenced by earthquake acceleration and ground stress. Resistivity data retrieval is carried out using the Wenner configuration method. The results showed that 1) the elevation of the measurement location was in the range of 18 meters to 59 meters, 2) The range of resistivity values at the liquefaction area in Balaroa village was 2 Ωm to 10000 Ωm, and 3) 4 types of soils were obtained at the research site consisting of water-saturated Alluvium layer, Conglomerate rock destruction, Weathered Granite, and Granite chunks, All measurement lines are shatter zones seen in resistivity cross-sectional patterns that do not show stratigraphic laminated sedimentary patterns good, At line-1 of Balaroa, traces of fault depression were found, which was interpreted as still part of the western Palu-Koro fault zone, and in line-3 of Balaroa, an ancient river channel was found that was trending almost West-East.