Dan H. Shugar, Katherine R. Barnhart, Mira Berdahl, Jacqueline Caplan-Auerbach, Göran Ekström, Aram Fathian, Marten Geertsema, Stephen Hicks, Bretwood Higman, Erin K. Jensen, Ezgi Karasözen, Patrick Lynett, John Lyons, Thomas Monahan, Gerard Roe, Kristian Svennevig, L. Toney, Maximillian Van Wyk de Vries, Michael E. West
-cubic meter landslide struck Tracy Arm fjord in Alaska. The landslide was preconditioned by glacial retreat caused by climate change. The resulting 481-meter runup megatsunami followed an initial 100-meter-high breaking wave traveling at >70 meters per second. The landslide was preceded by several days of microseismicity, which increased in rate and magnitude until ~1 hour before failure. The landslide produced globally observed long-period seismic waves equivalent in size to a moment magnitude 5.4 earthquake. A long-period (~66 second) global seismic signal, produced by a landslide-induced seiche trapped within the fjord, persisted for up to 36 hours, the second time a days-long seiche had thus been observed. With fjord regions increasingly visited by cruise ships, and climate change making similar events more likely, this unanticipated, near-miss event highlights the growing risk from landslides and tsunamis in coastal environments.