LAUSR

Abstract Following the 7.5-Mw earthquake that occurred on 28 September 2018, a series of field surveys were performed to further understand the impacts of the resulting tsunami. Tsunamis initiated by strike-slip earthquakes are rare. Other factors are suspected to have contributed to this unusual tsunami. One of these factors was the subaerial landslides around Palu Bay, which were observed at several locations. This paper aims to investigate the characteristics of the tsunami based on the flow depths/heights, tsunami inundation, wave direction and tsunami debris. The surveys were performed from 12 October to 10 November in 2018. The flow depths were measured at 84 locations along the bay. Higher tsunami depths were found at Talise Beach, which is on the closed end of the bay. The southwestern edge of Palu Bay had lower tsunami depths compared to the northeastern edge. The highest flow depth measured in this study was at the village of Tondo, at the northeastern edge of the bay. The sporadic subaerial landslides that generated the tsunami were implicated by the direction of the tsunami waves, which were inconsistent with nearby data. The combination of the complicated tsunami characteristics and the minimum level of tsunami mitigation contributed to the large number of casualties during the 2018 Palu Bay tsunami.