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NOAA NCTR research product
Not an official forecast

On January 15, 2022, the Hunga Tonga-Hunga Ha'apai volcano (20.5°S 175.4°W), located about 60 km north of Fua'amotu, the main island of Tonga, violently erupted with a powerful explosion, culminating the period of volcanic activity that started in December of 2021. The explosion generated a strong tsunami that was recorded all over the Pacific Ocean, the waves were also reported in other ocean basins, including the Caribbean and Mediterranean seas.

Multiple tsunami generation mechanisms were at play during this event and not all of them are currently fully understood. Research is on-going to analyze all the event data for conclusive tsunami source assessment.

This page provides an overview of the initial analysis of the tsunami using the tsunami forecast modeling tools developed at NCTR and the real-time tsunami data available for this event. The goal of this preliminary analysis is to develop forecast capabilities for tsunami events of this type. The components of this page will be updated when new data and new models are available.

Tsunami Data

The tsunami was detected by virtually all available DART systems (Deep-ocean Assessment and Reporting of Tsunamis) and the majority of coastal sea-level gauges around the U.S. and the Pacific.

The Bottom Pressure Recorders (BPRs) of the DART systems recorded the waves of the Tonga tsunami led by the air pressure waves from the volcano explosion (Figure 1). The atmospheric pressure waves are responsible for the discrepancy in arrival time between model and observations reflected in the time series plots. That mixture of data in the DART records from independent generation mechanisms complicated the tsunami source inversion process for modeling the event.

Preliminary Modeling

The preliminary model of the Tonga volcano tsunami was developed by inverting the parts of the DART records that do not include the air pressure signature. A custom set of 9 Green's functions were computed in real time for the DART data inversion using Gaussian shapes as unit sources at the site of the volcano.

Graphs of model inversion results using three DARTs
Figure 1. Model inversion results using three DARTs. The model (red) is the best fit for the DART data (black) and uses a combination of 9 Gaussian unit sources. The fit process excludes the first wave recorded at DART, interpreted as the pressure wave from the volcanic explosion. The green circles indicate the arrival of the atmospheric pressure wave at the DART location.
Click to see larger image

The simulation results are obtained using MOST propagation model and high-resolution inundation forecast models that are available for several tide-gauge locations.

Maximum computed tsunami amplitudes
Figure 2. Maximum computed tsunami amplitudes are depicted with filled colors.
Click to see larger image
Tsunami propagation
Figure 3. Animation of tsunami propagation.
Click for animation

Comparison of the measured tsunami recorded at tide gauges (black) with model results (red) is presented in the following links:

The model results are preliminary. The tsunami source is estimated with the described inversion procedure. While there are significant discrepancies between model results and tide gauge observations, especially some arrival time differences, the amplitudes are mostly reproduced, even for far-away locations. The difficulty inverting the mixed data of DART records may be the main reason for the model deficiencies.

Source: 39.26*sc3 + 87.57*sc4 + 65.66*sc7 + 62.99*sc8 (Unit sources not directly available from the NCTR's unit source database.)

Disclaimer: The models on these pages show the results of ongoing research to enhance tsunami science and to improve NOAA operational tsunami forecasts. These products were developed during or shortly after the tsunami event, are intended for research use, and are not an official forecast. They should not be used as the basis of any public or private policy decisions. Please contact NCTR to find if there are more detailed follow-on analysis results.

Media Contacts

NOAA Public Affairs Monica Allen - 301-734-1123
NWS Public Affairs Susan Buchanan - 301-713-0622

When using information from this page, please credit NOAA / PMEL / Center for Tsunami Research

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