Waves from Tonga eruption reach 90m - 9 times higher than 2011 Japan tsunami

Waves from Tonga’s volcanic eruption reached 90 metres, nine times higher than the 2011 Japanese tsunami

The eruption produced an initial wave 90 meters high.Credit: University of Bath

The January 2022 eruption of the underwater Hunga Tonga Ha’apai volcano in Tonga produced an initial tsunami wave height of 90 metres, about nine times the height of the highly damaging tsunami of the 2011 Japanese tsunami, new research has found.

The eruption should serve as a wake-up call for international groups looking to protect people from similar events in the future, an international team of researchers say, claiming that volcano-based tsunami detection and monitoring systems are 30 years behind similar tools used to detect them. Years of earthquake-based events.

Dr Mohammad Heidarzadeh, Secretary-General of the International Tsunami Committee and Senior Lecturer in the Department of Architecture and Civil Engineering at the University of Bath, authored the study with colleagues from Japan, New Zealand, the UK and Croatia.

In contrast, the largest tsunami waves from earthquakes prior to the Tonga event were recorded to an initial height of 10 meters following the 2011 Tohoku earthquake near Japan and the 1960 Chile earthquake. They are more destructive and the waves are wider as they get closer to land.

Dr Heidarzadeh said the Tonga tsunami should serve as a wake-up call for more preparation and understanding of the causes and signs of tsunamis caused by volcanic eruptions. He said, “The Tonga tsunami tragically killed five people and caused massive damage, but the impact could have been greater if the volcano was closer to human communities. The volcano is about 70 kilometers from Tonga’s capital, Nuku’alofa — This distance greatly reduces its destructive power.”

“This is a huge and unique event that underscores the need for us internationally to invest in improving systems to detect volcanic tsunamis, which are currently about 30 years behind the systems we use to monitor earthquakes. We are ill-prepared for volcanic tsunamis. .”

The research was conducted by analyzing oceanographic data records of atmospheric pressure changes and sea level oscillations, combined with computer simulations validated using real-world data.

Waves from Tonga eruption reach 90m - 9 times higher than 2011 Japan tsunami

Snapshots of tsunami propagation at different times for the Tonga tsunami on 15 January 2022 from our source model S6.Credit: University of Bath

The team found that tsunamis are unique because the waves are created not only by water displaced by volcanic eruptions, but also by huge waves of atmospheric pressure that circle the Earth multiple times. This “dual mechanism” created a two-part tsunami – an initial wave created by an atmospheric pressure wave followed by a second wave displaced by the erupting water more than an hour later.

This combination meant that the initial wave was not detected by the Tsunami Warning Center because they were programmed to detect tsunamis based on water displacement rather than atmospheric pressure waves.

The team also found that January’s tsunami was one of very few tsunamis large enough to travel globally — it was recorded in all of the world’s oceans and oceans, from the western North Pacific coast of Japan and the United States to inland coasts. Mediterranean.

The paper, co-authored by colleagues from GNS Science in New Zealand, the Japan Society for the Development of Earthquake Prediction, the University of Split in Croatia, and Brunel University in London, was published this week in Ocean engineering.

Dr Aditya Gusman, Tsunami Modeller, Geoscience Service New Zealand, said, “The 2018 Anak Krakatau and 2022 Hunga Tonga-Hunga Ha’apai eruptions clearly show that coastal areas around volcanic islands are at risk of being attacked by damaging Tsunamis. While it is best to keep low-lying coastal areas completely away from residential buildings, such a policy may not be practical in some places, as volcanic tsunamis can be considered rare events.

Co-author Dr Jadranka Šepić, from the University of Split, Croatia, added: “It is important to have an effective early warning system, which includes real-time warnings and education on what to do in the event of a tsunami or warning – such a system can save lives. Also, in volcanic areas, monitoring of volcanic activity should be organized, and it is always a good idea to do more high-quality research on eruptions and hazardous areas.”

Another study published in June by atmospheric physicist Dr Corwin Wright at the University of Bath found that the Tonga eruption triggered atmospheric gravity waves that reached the edge of space.

Scientists offer explanation for special Tonga tsunami

More information:
Mohammad Heidarzadeh et al., Estimating the source of water displacement from the eruption of the Tonga volcanic tsunami on 15 January 2022 from tsunami spectroscopy and numerical simulations, Ocean engineering (2022). DOI: 10.1016/j.oceaneng.2022.112165

Provided by the University of Bath

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