Diverse tsunamigenesis triggered by the Hunga Tonga-Hunga Ha’apai eruption

Abstract

On the evening of 15 January 2022, the Hunga Tonga-Hunga Ha’apai volcano 1 unleashed a violent underwater eruption, blanketing the surrounding land masses in ash and debris 2 , 3 . The eruption generated tsunamis observed around the world. An event of this type last occurred in 1883 during the eruption of Krakatau 4 , and thus we have the first observations of a tsunami from a large emergent volcanic eruption captured with modern instrumentation. Here we show that the explosive eruption generated waves through multiple mechanisms, including: (1) air–sea coupling with the initial and powerful shock wave radiating out from the explosion in the immediate vicinity of the eruption; (2) collapse of the water cavity created by the underwater explosion; and (3) air–sea coupling with the air-pressure pulse that circled the Earth several times, leading to a global tsunami. In the near field, tsunami impacts are strongly controlled by the water-cavity source whereas the far-field tsunami, which was unusually persistent, can be largely described by the air-pressure pulse mechanism. Catastrophic damage in some harbours in the far field was averted by just tens of centimetres, implying that a modest sea level rise combined with a future, similar event would lead to a step-function increase in impacts on infrastructure. Piecing together the complexity of this event has broad implications for coastal hazards in similar geophysical settings, suggesting a currently neglected source of global tsunamis.

Water waves generated by moving atmospheric pressure: theoretical analyses with applications to the 2022 Tonga event

“…In the Tonga event, the atmospheric pressure is nearly axisymmetric and decays in the radial direction (Amores et al 2022;Lynett et al 2022). In this section, approximate solutions are sought for axisymmetric shallow-water waves being forced by an atmospheric pressure field.…”

“…surface profile η. For the Tonga event, the atmospheric pressure wave is long (∼800 km) and propagates within the supercritical regime (Fr ≈ 1.5) (Amores et al 2022;Lynett et al 2022). Thus the free surface elevation of the leading locked wave has the same sign and shape as the atmospheric pressure wave, and (2.19) can be used in (4.1) to find the following relationships:…”

“…Based on the DART data at these stations, the Froude numbers range from 1.48 to 1.58, with average 1.54, confirming that the Tonga event is under the supercritical condition. During the event, the atmospheric pressure wave travels at the average velocity C p ≈ 1100 km h −1 in the Pacific Ocean (Lynett et al 2022), and the wave celerity of long water waves can be estimated as C ≈ 713 km h −1 , corresponding to average depth 4 km, representative of the Pacific Ocean. The theoretical time differences in the arrival times of the leading locked wave and the trailing free wave are listed in the second to last column in table 1.…”

“…In addition, a trailing train of tsunami waves, propagating at long water wave celerity √ gh, was also recorded in the Pacific Ocean. These trailing tsunami waves have been attributed to other tsunami generation mechanisms associated with the volcano explosion and collapse (Lynett et al 2022).…”

Tsunami Runup and Inundation in Tonga from the January 2022 eruption of Hunga Volcano

“…1). Hunga is often referred to by the names of two small islands Hunga-Tonga and Hunga Ha'apai that are located on the submarine caldera's northern rim (Cronin et al, 2017), During the rst 45 minutes of this eruption, a massive atmospheric pressure wave and a series of tsunamis were generated and observed around the world (Carvajal et al, 2022, Lynett et al, 2022.…”