Reconstruction of the 2018 Palu Tsunami based on Tectonic Earthquake

Abstract

On September 28, 2018, Indonesia was devastated by a 7.5Mw earthquake that triggered a tsunami off of the coast of Palu Bay, Central Sulawesi. This incident was puzzling because strike-slip fault earthquakes rarely generates destructive tsunamis. Previous studies have shown that the 2018 Palu tsunami had not been generated solely by a tectonic source, but there had been other motions such as submarine landslide which could have potentially contributed to and intensified the main tectonic tsunami. Such hypothesis was concluded based on the significant difference between the result of numerical simulation and the tide gauge’s record. The purpose of this study is to further analyze the conclusion of this hypothesis by comparing the result of numerical simulation with the post-tsunami survey in several observed points. The observed points were located at two tide gauges, Pantoloan and Mamuju, as well as twenty-two other points located both within and outside of Palu Bay. The comparison of simulation results with observed data showed a 30-minute arrival delay of the tsunami in Mamuju. Maximum inundation in observed points also showed a difference of 0.2–6 meters compared with post-tsunami survey. The inundation areas were significantly different at a range of 1–7 km2, which indicated other motions that could have contributed to the Palu tsunami.