A 7.7 earthquake off the west coast of Canada on Saturday evening triggered a series of tsunami alerts for the Pacific and some coastal evacuations in Hawaii. Although the quake was fairly large — the biggest Canada has seen in some 60 years — it produced waves of only about a metre in Hilo, Hawaii, and less than about 0.3 metres in California and British Columbia.
The quake originated on the Queen Charlotte fault, which lies a few hundred kilometres west of the mainland, and was also responsible for an 8.1 quake in 1949. This fault mostly produces horizontal movement of tectonic plates, rather than the large vertical movements that typically shift ocean waters and generate large tsunamis. But a 2010 Geological Survey of Canada review of the fault suggests that it is capable of producing large waves.
The Pacific Tsunami Warning Center issued a bulletin less than ten minutes after the quake, reassuring that “a widespread destructive tsunami threat does not exist based on historical earthquake and tsunami data”. Nevertheless, the dangers of more active seas and coastal flooding triggered sirens in Hawaii, where some beaches and ports were closed, and traffic jams were generated as people fled inland.
No major damage was reported from the earthquake. The Queen Charlotte area is not heavily developed or populated.
Smaller quakes have caused larger waves for Hawaii in the past. In 1946, a magnitude-7.1 earthquake from the Aleutian Islands flooded downtown Hilo, killing more than 150 people and causing US$26 million in damages.