Areal strain responses to Lamb waves generated from 2022 Hunga-Tonga volcano eruption

On 15 January 2022, the largest Hunga-Tonga volcano eruption ever recorded produced a plume, causing atmospheric waves that propagated from the volcanic epicenter to the surrounding areas. Although studies have reported multi-parameter responses to this eruption, the far-field areal strain on the surface remained underexplored. Here we adopted 7 parameters of the strain tensors in the far-field about 8700–13,500 km from the volcano epicenter to study their responses to the generated Lamb waves from the eruption. The results showed that at least triple perturbations could be picked up clearly from the strain curves, indicating Lamb waves propagated several times around the globe from opposite directions at the same speed of approximately 320 m/s, each lasting about 30.5 h. For the surface shear strain, we rotated the coordinates system to the radial and tangential direction of Lamb wave propagation, and found that the amplitude of the radial strain was twice that of the tangential strain. Additionally, the principal strain reflected by the Mohr strain circles is consistent with the propagation direction of Lamb waves. The results indicate that the volcano eruption caused fluctuations via the air-rock interaction induced by Lamb waves in the air.