Finding the sources of tsunamis in the Southwest Pacific: A case study on Niuatoputapu, Tonga. (APSF 22004)

APSF 22004 | Amount: $36,620 | Project Leader: A Lau | Project Period:

A project undertaken at The University of Queensland, and supervised by Dr Annie Lau.

The volcanic-generated tsunami in Tonga in early 2022 is a timely reminder of the devastating impact of such events on coastal settlements. Understanding past tsunami occurrences, including wave magnitudes, sources, and recurrence intervals is crucial for tsunami hazard assessments. Finding and analysing coastal sediment layers created by past (including pre-historical) tsunamis can tell us how high the waves were, how far they flooded, and how often they occurred.

This project focuses on Tonga, one of the oldest Polynesian settlements. From the hazard perspective, Tonga is in a high-hazard location as the Tonga trench is the world’s fastest converging subduction zone. The nation has experienced at least four earthquake tsunamis and two volcanic tsunamis in history, including in 2009 when it was badly affected by the Samoa earthquake tsunami, but prehistoric tsunamis’ magnitude and recurrence patterns remain unknown, non-earthquake tsunami sources such as areas prone to submarine landslides are unidentified. This project aims to address these knowledge gaps by examining the physical (e.g. geomorphic and sediment) properties of the northern Tongan island of Niuatoputapu with the guidance of local Indigenous knowledge, to reconstruct long-term tsunami history for more accurate analysis of future hazard risk in the northern Tonga region.

Coastal settlements on Niuatoputapu Island

Niuatoputapu’s morphology, comprising a broad shallow, low-elevation shelf, is ideal for recording tsunami wave inundation. We aim to generate a history of previous (historical and ancient) tsunami events, including their timing, magnitude and wave direction. We will identify potential tsunami source locations to inform the local community and wider Tonga of the probability of tsunamis generated not only by earthquakes. We also aim to use evidence from the landscape and sediment cores to reveal Niuatoputapu’s sea-level and environmental change history over the past 5000 years. This can provide baseline information for studying climate change impacts on southwest Pacific islands. 

he project outcomes will benefit Pacific Island Countries by increasing the understanding of tsunami sources in the southwest Pacific, informing disaster management practices to mitigate the risk of natural hazard events, and enhancing human welfare in the Pacific region.