Tsunami hazards in East Indonesia from seismic and non-seismic sources: Historical observations and modeling

Abstract:

East Indonesia underlies in a complex and seismically-active region. With the majority of the region covered by the sea, East Indonesia is vulnerable to tsunamis triggered by earthquakes, landslides, and volcanic sources. This region has experienced more tsunamis than the western part of Indonesia (Sumatra-Andaman and Java) but fewer studies have been conducted for East Indonesia compared to the west. Moreover, previous tsunami hazard assessments done in West Indonesia have been mainly focused only on tsunamigenic earthquake sources and other types of source were greatly overlooked. This study shows the complexity of tsunami hazards posed to East Indonesia from three types of source: earthquake, underwater landslide, and volcano flank-collapse.

Firstly, we model tsunami propagation from a hypothetical Mw7.8 earthquake from the Flores back-arc thrust zone. We found that small changes in the earthquake parameter is resulting in different patterns on tsunami and seismic hazards for the Flores Sea region. Second, the Makassar Strait might has experienced landslide tsunamis based on existing marine bathymetric and seismic surveys, but such tsunami hazards were not studied. We assess potential tsunami hazards from hypothetical submarine landslides based on marine sediment deposit identified from seismic data. Lastly, volcanic islands are evenly distributed in East Indonesia and some of them had generated tsunamis in the past. We model a flank-collapse scenario from the Ruang Volcano to study the 1871 tsunami and validate the modeling results against historical runup data.

In addition, many potential tsunami sources that need further investigation. Among which are: the Banda Detachment, a very low-angle normal fault, other potential underwater landslides in the region, as well as volcanic-tsunami source mechanisms.