VELOCITY OF LIQUEFACTION-INDUCED LANDSLIDE IN JONO-OGE TRIGGERED BY 7.5 Mw PALU EARTHQUAKE

Abstract

On September 28, 2018, a 7.5 earthquake in Palu, Indonesia, triggered multiple phenomena including liquefaction, landslides, and tsunamis. A video recorded the landslide in Jono-Oge, located near Palu Valley, and was captured by a local citizen from his home, which was carried along by a debris flow. The video shows that the land moved like water, carrying buildings, and trees, whereas some other structures remained. The moving camera raises difficulties in the analysis because it operates with various degrees of movement. However, a velocity estimation is possible by applying two types of camera-angle analysis using non-moving buildings captured on the video as a point of reference. In this case, a red roof house and a steel tower were used. We identified that the camera moved from east to west and started at an elevation of 70 m, located 1000 m from the top of the Jono-Oge landslide at the irrigation canal. At an elevation of 68 m, the landslide velocity was 5.1 m/s and slowed down to 4 m/s after moving 200 m to an elevation of 62 m. This deceleration might correspond to a decrease in the slope inclination, from 3% to a gentler slope of only 1%. This result will be informative for the parameters used in landslides and landslide-induced tsunami simulations.