Simulation of the Submarine Landslide Tsunami on 28 September 2018 in Palu Bay, Sulawesi Island, Indonesia, Using a Two-Layer Model

Kwanchai Pakoksung, Anawat Suppasri, Fumihiko Imamura, Cipta Athanasius, Amalfi Omang, Abdul Muhari

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)

Abstract

The strike-slip earthquake on 28 September 2018 (Mw 7.5) along the Palu-Koro fault on Sulawesi Island has raised concerns about the potential impact of tsunamis generated by submarine landslides in Palu Bay, Indonesia. The horizontal displacement of the Palu-Koro fault generated landslide tsunamis that covered Palu Bay, creating wave-related hazards along the coastal area. Based on the unusual amount of information on this tsunami, this study investigated possible sources using the available preliminary data. The generation of comparatively small tsunamis by coseismic seafloor deformation is omitted, and only tsunamis generated by submarine/subaerial landslides are analyzed in this study. Two-layer modeling (soil and water) based on the shallow-water equation was used to simulate the tsunami propagation in the bay with severe, moderate, and minor impacts. The accuracy of the model was validated based on the waveform at the Pantoloan tidal gauge and trace data. The tsunami heights from a combination of small to large submarine landslides could reach up to 3.0–7.0 m along the Palu shores. This model focused on studying the effects of the tidal level on coastal inundation in Palu Bay, using the 2018 Palu tsunami event as a benchmark scenario, to demonstrate the capabilities of the model. One result shows that, regardless of the tidal level, the 2018 Palu tsunami, which occurred during high tide, will always result in flooding, with a maximum tsunami height of up to 7.0 m above mean sea level. The main results suggest two causes for this tsunami event: the tsunami source and the topography. First, the model requires one large source at the bay entrance to reproduce the arrival time (approximately 5 min) and the large wave observed at the Pantoloan gauge. To reproduce the later waves, small sources in the bay (S1–S6) and minor large sources (L2 and L3) are needed. Second, the datum correction for the terrain is changed to improve the accuracy of the water level. Additionally, the removal of buildings from the topography is important to achieve highly accurate flow depths and to obtain an inundation area close to the real situation. The impacts along the coastline of Palu Bay from peak waves can be used to identify tsunami hazards in the area in the future.

Original languageEnglish
Pages (from-to)3323-3350
Number of pages28
JournalPure and Applied Geophysics
Volume176
Issue number8
DOIs
Publication statusPublished - 2019 Aug 1

Keywords

  • Palu tsunami
  • Tsunami
  • numerical simulation
  • submarine landslide tsunami
  • two-layer modeling

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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