Estimating the eruption-induced water displacement source of the 15 January 2022 Tonga volcanic tsunami from tsunami spectra and numerical modelling

The 15 January 2022 Tonga volcanic tsunami was a unique event as it was the only event after the 1883 Krakatau volcanic tsunami that created waves by a dual-mechanism generation process comprising atmospheric pressure waves and eruption-induced water displacements. Here, we study 22 tide gauge waveforms, eight DART (Deep-ocean Assessment and Reporting of Tsunamis) records, eight air pressure time series, apply spectral analysis, and conduct numerical modelling to develop a source model. Our source model accounts only for the contribution of eruption-induced water displacement. The maximum overall coastal tide gauge amplitudes were in the range of 4.2-148.8 cm, whereas DARTs registered maximum amplitudes of 3.6-21.4 cm. We identified the dominant tsunami periods due to the localized water displacement mechanism as 10-17 min and 4-7 min. The waves generated by atmospheric pressure waves had a period of 7-10 min and an amplitude of 9-19 cm on coastal tide gauges; the corresponding values for DARTs were 30-60 min and 4.2-15.7 cm. Modelling showed that the eruption-induced water displacement source had a characteristic initial length of 12 km, a maximum initial amplitude of 90 m, and a volume of 6.60 x 10(9) m(3).

Automated summary

The 15 January 2022 Tonga volcanic tsunami was a unique event where waves were created by a dual-mechanism generation process involving atmospheric pressure waves and eruption-induced water displacements. The study found that the maximum overall coastal tide gauge amplitudes ranged from 4.2 to 148.8 cm, while DARTs recorded maximum amplitudes of 3.6 to 21.4 cm.