Hydrodynamics of Palu Bay during the Event of 2018 Palu Earthquake and Tsunami

Abstract

The devastation of coastal area in Palu Bay few minutes after the September 28th, 2018 Sulawesi earthquake showed high variation of tsunami arrival time as well as the tsunami run-up and inundation. Recent findings showed that both local submarine landslides and the normal-slip components inside the Palu Bay may contribute to the generation of tsunami. However, the fact that the event occurred during high tide, the hydrodynamic characteristics of this narrow bay and their role in the dynamics of the generated of tsunami were unknown. Hydrodynamics simulation (Mike21-flow model) using the latest available bathymetry field data (the 2018 deep water of the Indonesian navy data and 2015 shallow water of the BIG data) was conducted to investigate the variation of sea levels and tidal currents within the bay during the event of earthquake and tsunami or within the first 8 minutes timeframe. Results showed that significant increase of water elevation up to 6 cm and current velocity up to 1 cm/s directed towards the city of Palu were observed that may contribute to the dynamics of the tsunami e.g. the speed of tsunami arrival time and the transformation of tsunami. Therefore, considering that multiple tsunami arrivals were in few minutes after the earthquakes, the hydrodynamics of Palu Bay during the event should also be considered in future tsunami simulation scenarios.

Keywords

• palu,
• tsunami
• erthquake
• tides
• hydrodynamic