Monitoring Areas of Potential Liquefaction Based on Water Index in Padang City Indonesia Using Landsat Images

Abstract Padang City is located on the west coast of Sumatra Island, facing a subduction zone. This subduction zone is an active area where the Indo-Australian Plate has infiltrated the Eurasian Plate, resulting in the city of Padang being earthquake-prone. Besides being able to knock down buildings, earthquakes can also cause liquefaction. One of the factors causing liquefaction is the high water index in the area. In this study, monitoring the potential liquefaction in the Padang City area was carried out based on the level of the water index. This type of research is applied research. We carried out NDWI (Normalized Difference Water Index) extraction using Landsat images with NIR and SWIR bands to monitor the water index. This study aims to monitor Padang's potential liquefaction area using Landsat images before and after the 2009 earthquake and 2020 conditions. The results of this study are a water index map in percentage form for Padang. The conducted research revealed that 11 subdistricts in Padang had a water index ranging from 0 to 100%. Bungus Teluk Kabung Subdistrict has the highest water index, while Padang Timur has the lowest. Water index monitoring can be used as a reference for urban development.