Ultra-long period and small-amplitude tsunami generated following the July 2020 Alaska Mw7.8 tsunamigenic earthquake

The July 2020 Mw7.8 Alaska tsunamigenic earthquake was a fresh call for potential large tsunamis associated with the Aleutian subduction zone. second largest ever-recorded worldwide (Mw 9.2) occurred in this zone 1964 indicating its massive and tsunami risk. Our analysis of revealed that it involves very long period waves (51–64 min) which is unusual an earthquake. coastal amplitude small (~0.5 m) much smaller than usually expected from size. Here, through numerical simulations spectral analyses, we explain ultra-long tsunami. using analytical equation showed can be reproduced shallow water depth around source region (100–200 length coseismic deformation area (~100 km). By comparing event four other similar-size similar-mechanism earthquakes (thrust Mw7.8), attribute relatively to deep focal (28 km) extremely region.