2018 Sulawesi tsunami explained by sub marine landslide
Published: 12 December 2018
Tsunami land slide model
The reported tsunami heights cannot be explained by conventional earthquake slip-displacement mechanism. Initial computer simulation made by experts from the Dutch research institute Deltares, the peak tsunami wave caused by the earthquake reached only ~0.4 m at Palu and ~0.3 meter at Donggala. Videos taken from the airplane that has just departed Palu city just after the event showed a number of coastal landslides. However, these appear to be relatively small slides incapable of generating the observed tsunami heights and run-up. Deltares experts explain that one or more submarine landslides with larger dimensions must have occurred in the area.
Multiple source locations
Deltares experts Deepak Vatvani, Maarten van Ormondt and Ap van Dongeren localized a number of possible large landslide sources using visual inspection of sonar charts of the bottom sea obtained from internet (www.navionics.com). These sources are input into a Delft3D hydrodynamic computer model as instantaneous bed displacements, without considering the landslide kinematics. By combining these sources with the initial earthquake source large tsunamis are generated in the Bay of Palu, which match the observed flooding pattern and flood heights in Palu.
Deepak Vatvani (tsunami expert Deltares): “Up till now, most tsunami warning systems only account for earthquake mechanisms. This event in Sulawesi shows that tsunami caused by landslides need to be included as well”.
Next steps: mapping underwater topography
In order to improve the computer models and forecasting in the future, there is a need for accurate mapping underwater topography and a better understanding of submarine landslide mechanism and also how to incorporate these effects in tsunami warnings.