What was the major source in the event of 2018 Sulawesi tsunami?

The tsunamis in the event of 2018 Sulawesi earthquake and tsunami (SET) occurred after an earthquake of magnitude 7.5. However, it is very difficult for such a strike-slip earthquake to trigger a tsunami with a 10-m flood depth. The causes of this tsunami events remain unknown. A submarine landslide, an additional seabed vertical displacement from the bending fault, local bathymetry effect, large-scale liquefaction into the water, and seiche may play roles. Data collected are gauge data, bathymetry data, official announcement, movie clips from social media, and filed survey data from many countries. However, we found conflicts between different type of data and have to be used very carefully. The impact intensity analysis method (IIA) was utilized to analyze the tsunami source in the SET event. The IIA method can quickly filter out the areas with low impacts of the tsunami sources and effectively reduce the number of tsunami scenarios. In this study, we performed scenario study by simulating the tsunamis generated by above-mentioned sources. The results show that the wave height contributed at Pantoloan by pure seismic motion is less than 0.5m which is far away from the observation. However, this simulated seismic wave matches the gauge record at Mamuju, which is outside the Palu bay. The results from a single in-the-bay landslide and seiche are away from the waveform and arrival time at Pantoloan gauge. However, combining many small landslide-tsunami sources, the small waves became large waves with wave period and wavelength 5 to 10 times longer than the one from a single landslide source. We conclude that there were two tsunami sources in this event. One was the seismic wave which affects the area outside the Palu bay. Another was the landslide tsunami in the Palu bay. The detailed results will be presented in the full paper.