Large-scale flowslide in Sibalaya caused by the 2018 Sulawesi earthquake

Abstract

On 28th September 2018, an earthquake of Mw 7.5 hit the Central Sulawesi province in Indonesia. This was followed by liquefaction-induced large-scale ground flows in several areas in Palu city and its neighborhood. A significant characteristic of the ground flows at these sites was that large volume of soil slid downhill along gentle topographic gradients and travelled long distances (more than several hundred meters). To gain a better understanding of the fundamental mechanisms contributing to ground flows, this geo-disaster report summarizes a site investigation conducted at Sibalaya, one of the sites where massive ground flows were observed. We conducted interviews to reveal the time sequence of the event, including the main shaking that was followed by a sudden drop of the ground surface, the time at which the massive ground flow was initiated (with an extremely loud sound), as well as the change in the water level of wells. Water leakage from the unlined irrigation channel was confirmed to contribute significantly to the increase in the ground water level in this area, which thus increased the liquefaction potential. In situ tests, including eight large trench excavations and dynamic cone penetration tests, were carried out, which helped identify the liquefied and largely sheared layers. An analysis of the change in topography using satellite images and UAV photos also played an important role in capturing the overall picture of the event. Finally, a hypothesized mechanism for the extremely long slide was discussed.

Access to Document

Other files and links

• Link to publication in Scopus
• Open Access Version Available

Fingerprint