Item

Abstract

Hazardous tsunamis are generally generated by megathrust earthquakes in subduction zones, like the 2004 Mw 9.1 Sumatra-Andaman earthquake and the 2011 Mw 9.0 Tohoku earthquake. However, recent severe tsunami impacts from atypical sources gain remarkable attention from scientists in related fields. The 2020 Samos normal-faulting earthquake of Mw 6.9 produced an unexpected maximum tsunami runup of up to 3.8 m. The 2022 Hunga Tonga–Hunga Ha’apai volcanic eruption generated unusual tsunami through the air-sea coupling of atmospheric acoustic-gravity waves and ocean surface, which is widely observed in the global oceans. Here, we present the tsunami source characteristics and hydrodynamic behaviours of the two aforementioned atypical cases to investigate the intensifying factor for both tsunami events. We adopt an integrated approach, including source inversion and tsunami modelling, together with spectral and statistical analyses of tsunami waveforms. We find the 2020 Samos tsunami is exacerbated by not only the favorable source conditions for tsunami generation but also the near-source bathymetric morphology. For the 2022 Tonga volcanic tsunami event, we identify four distinct tsunami wave components which are associated with their complex generation mechanisms ranging from air–sea couplings to seafloor crustal deformation during the volcanic eruption. The unexpected tsunami hazards from the atypical sources highlight the significance of various unusual mechanisms for tsunami generation and some favored conditions in intensifying tsunami behaviours. Both tsunami events call for technical improvement for traditional seismic warning system. References Hu, G., et al. (2022) https://doi.org/10.1029/2022JB023961 Hu, G. et al. (2022). https://doi.org/10.5194/nhess-2022-200