Analyzing the susceptibility for coastal and submarine landslides and their potential to trigger tsunami waves

Tsunamis generated by submarine or coastal landslides are a growing area of scientific interest. Events like the 2018 tsunami in Palu, Indonesia, have highlighted their destructive potential. Landslides can generate extremely high tsunami waves, but typically have a limited propagation range beyond 100 km. Areas close to the landslide are most affected. Unfortunately, early warning systems are not effective for this type of tsunami due to the short warning time interval between wave initiation and coastal impact.

This study aims to analyze the coastal and submarine landslide susceptibility for coastal areas. Limited data availability, including high-resolution bathymetric data and historical landslide tsunami catalogs, poses a major challenge. A heuristic model is used, incorporating historical case studies to calibrate and weight the parameters. Geologic, morphologic, and geometric parameters of coastal areas are considered.

First results show a high correlation of landslides generated during the Palu earthquake with the size of catchment areas of rivers entering the ocean. This parameter is strongly related with the sediment load that is transported into the ocean. High sedimentation rates might lead to the formation of thick, unconsolidated sediment layers., which are susceptible to landslides. This correlation will be further analyzed.

The results of this susceptibility mapping can help raise the awareness of the risks associated with landslide tsunamis. Even minor earthquakes, not expected to trigger tsunamis, could induce submarine or nearshore landslides and generate a tsunami in vulnerable areas. Consequently, adapting tsunami evacuation strategies to account for landslide-induced tsunamis may be required in these areas.