Geotechnical damage in the 2018 Sulawesi earthquake, Indonesia

On September 28th, 2018, at 18:02 local time (10:02 UTC), a strong earthquake of magnitude Mw = 7.5 struck Central Sulawesi Province, Indonesia. The epicenter was located at 0.256o south latitude and 119.846o east longitude, around 77 km from Palu city, and 20 km below the ground surface. To understand the damage caused by the earthquake, and find a solution to mitigate the geo-disasters in Indonesia, a preliminary investigation on the 2018 Sulawesi earthquake was conducted from 16 to 20 November 2018. This quick report focuses on ground displacements induced by fault movement and large-scale ground flow. During the survey, there is some geotechnical damage were found, such as ground displacement induced by fault movement, liquefaction, landslides, and large-scale ground flow in some certain areas. Large ground displacement was found in some particular areas, such as Kedondong, Pipa Air, Pangeran Diponegoro and Cemara streets in Palu city. The earthquake also triggered large-scale ground flow in some different sites, such as Balaroa and Petobo districts in Palu city and Jono Oge and Sibalaya Villages. The locations of large ground displacements appeared at surface coincide well with the estimated fault line. Therefore the large ground displacements were seems to be induced by the fault movement. Large ground flow caused severe damage to not only human but also houses and buildings. The mechanism of the large ground flow should be clarified in near future.