A team of scientists from the Japan Earthquake Research Institute has managed to identify a mysterious signal in the form of a “seismic wave” which took place minutes before the most powerful eruption ever recorded to date, at a volcano in the Pacific.
The eruption occurred in January 2022when the Hunga Tonga-Hunga Ha’apai underwater volcano exploded, emitting energy equivalent to 61 megatons of TNT or a magnitude 8.4 earthquake. According to this new study, two distant monitoring stations recorded a seismic wave about 15 minutes before of that violent explosion.
The researchers maintain that these types of early signals could be used to warn of other impending eruptions on remote oceanic volcanoes.
The authors of the study, published in the journal Geophysical Research Lettersdescribe the detected wave as a “seismic precursor” to the later eruptionboth caused by a collapse in a weak section of oceanic crust beneath the volcano’s caldera wall.
This fracture allowed both seawater and magma to spill into the area between the seabed and the volcano’s underground magma chamber, thus causing an explosive eruptionexplain the researchers.
Furthermore, the fracture caused what is known as ‘Rayleigh wave’a type of acoustic wave that moves along a solid surface, in this case, the Earth’s surface. This wave, which was not felt by humans, was detected 15 minutes before the main volcanic eruption on January 15, 2022, about 750 kilometers away, at seismic stations on the islands of Fiji and Futuna.
“Many eruptions are preceded by seismic activity“said Takuro Horiuchi, a graduate student in volcanology at the University of Tokyo and lead author of the study. “However, these seismic signals are subtle and are only detected several kilometers from the volcano,” he points out.
In this case, the researchers believe that this wave meant a precursor event and a possible cause of the massive eruption.
Study co-author Mie Ichihara, a volcanologist at the University of Tokyo, notes that “Early warnings are very important for disaster mitigation“. In this sense, he maintains that “island volcanoes can generate tsunamis, which are a significant danger.”
At the time of issue emergency alertsthe detection of this Rayleigh wave by distant instruments bodes well for future predictions, according to the authors. “At the time of the eruption, we didn’t think about using this kind of real-time analysis,” Ichihara says. “But maybe the next time there’s a major underwater eruption, local observatories can recognize it based on their data,” he concludes.
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