On 23 January 2018, a magnitude 7.9 earthquake occurred in the Gulf of Alaska at 1:35 am PT. A tsunami warning was issued for the west coast of Canada and the United States. The tsunami warning was cancelled at 4:40 am PT.

Ocean Networks Canada’s (ONC) real-time sensors detected the earthquake and the subsequent small tsunami that rippled out across the northeast Pacific (Figure 1).

Figure 1. The relative timing of the magnitude 7.9 Alaskan earthquake and the subsequent small tsunami as detected by ONC real-time sensors.

The resulting tsunami wave was relatively small because this was a strike-slip...