National Research Institute for Earth Science and Disaster Resilience (NIED) and the Earthquake Research Institute, the University of Tokyo have elucidated the global tsunami generation and propagation mechanism caused by the massive eruption of the Hunga Tonga-Hunga Ha’apai volcano in the Tonga Islands, South Pacific in January 2022, demonstrating that future tsunami research should consider not only earthquakes but also volcanic eruptions. The details of this study were published online in the U.S. journal “Science” on May 12, 2022.
On January 15, 2022, global tsunamis were generated following the massive eruption at the Hunga Tonga-Hunga Ha’apai volcano in the Tonga Islands of the South Pacific. These tsunamis propagated faster and arrived earlier at the global coast than those normally generated by subseafloor earthquakes, and were also observed at a far distance from the volcano.
This study simulated tsunamis caused by atmospheric waves called "Lamb waves" generated by the eruption in Tonga to reproduce the tsunami forerunner that propagated faster (about 300 m/s) than normal tsunamis from the observation records of the global ocean-bottom pressure observation network deployed on the seafloor. This demonstrated that the Lamb wave forcibly propagated the fast-travelling tsunamis across the entire Pacific Ocean. The subsequent tsunamis propagating at the speed of a typical tsunami (about 200 to 220 m/s) are considered to include waves generated by the resonance effects of tsunamis and “atmospheric gravity waves”, which should be verified by further data analysis and simulation in the future.
These results indicate that the generation mechanism of tsunamis caused by volcanic eruptions is different from that of tsunamis caused by subseafloor earthquakes. This made it clear it is important to pursue new tsunami research that also takes volcanic eruptions into account in the future.