LAUSR

On 15 January 2022, the Hunga Tonga-Hunga Ha‘apai volcano erupted, producing tsunamis worldwide including first waves which arrived more than 2 hours earlier than what is expected for conventional tsunamis. We investigated the generation and propagation mechanisms of the tsunami “forerunner,” and our simulation found that fast-moving atmospheric Lamb waves drove the leading sea height rise whereas the scattering of the leading waves related to bathymetric variations in the Pacific Ocean produced subsequent long-lasting tsunamis. Tsunamis arriving later than the conventionally expected travel time are composed of various waves generated from both moving and static sources, which makes the tsunami, due to this eruption, much more complex and longer-lasting than ordinary earthquake-induced tsunamis. Description Going on the lamb The Hunga Tonga undersea volcanic eruption was one of the most powerful recorded, with audible sound detected more than 10,000 kilometers from the source. Matoza et al. present infrasound and seismic recordings, along with other geophysical observations, that help to describe this event. An atmospheric lamb wave, characteristic of energetic atmospheric events, circled the planet four times and was similar to the 1883 Krakatau eruption. Kubota et al. detail how this lamb wave contributed to the global tsunami waves arriving much earlier than expected. The eruption also generated long-range infrasounds and ionospheric interations, along with a global tsunami. This set of observations will be helpful for disentangling the event and understanding the propagation of waves through the atmosphere and ocean (see the Perspective by Brodsky and Lay). —BG Observations of the Hunga Tonga volcanic eruption show a complex main event that was as energetic as the Krakatau eruption.