The sounds generated in the ocean by large submarine volcanic eruptions may help issue early tsunami alerts, according to a study led by researchers in New Zealand who analyzed the signals produced by the eruption of the Hunga volcano, in the Kingdom of Tonga, in 2022.
The team studied records from seismographs installed at various points across the Pacific, hundreds or thousands of kilometers from the volcano. Although the equipment recorded only normal, weak seismic signals, the researchers were able to identify, by adjusting the analysis to certain frequencies, a much stronger signal corresponding to sound waves propagating through the ocean.
One of the most expressive signals was detected in all directions from Hunga, reaching the Chatham Islands, about 2,600 kilometers away. The strong underwater noise arose approximately 90 minutes after the eruption began and about 45 minutes after the energy peak was released.
This interval led the researchers to conclude that the signal was not directly caused by the eruption itself. It would have resulted from the volcano collapsing onto itself, giving rise to the formation of a caldera.
It was precisely this collapse that provoked the largest tsunami recorded in Tonga during the Hunga eruption. The phenomenon caused three deaths and destroyed all the resorts on the main inhabited island of Tongatapu, as well as several coastal villages.
“We studied how to monitor eruptions in isolated submarine volcanoes through the sounds they produce in the ocean. From there, we discovered a possible way to issue alerts for volcano-induced tsunamis,” explains Shane Cronin, the study’s author.
The researcher emphasizes that large eruptions of submarine volcanoes can generate tsunamis of great size and destructive potential, but that it remains difficult to determine exactly what triggers them and when they may occur.
“In particular, we detected a huge sound signal that propagated in all directions from Hunga, easily reaching the Chatham Islands, 2,600 km away. This strong underwater noise occurred about 90 minutes after the eruption began and approximately 45 minutes after the eruption’s energy peak. Therefore, it was not generated by the eruption itself but by the volcano collapsing onto itself to form a caldera,” he says.
According to the researchers, these signals could in the future be used to identify and warn about tsunamis caused by caldera collapses or submarine landslides.
“By using these underwater sounds, we have a potential opportunity to identify and issue alerts for future volcanic tsunamis caused by caldera collapse or by submarine landslides. The main characteristic of sound waves is that they travel at 1.5 kilometers per second, more than seven times faster than tsunamis,” explains Shane Cronin.
The research thus suggests that sound could constitute a complementary tool to traditional tsunami monitoring systems, allowing a precious time window between the occurrence of a submarine volcanic event and the arrival of the destructive waves to coastal areas.
