June 23, 1946 Tsunami: British Columbia, Canada

There was a very strong earthquake in western Canada and in the northwestern United States. In the epicentral zone, it lasted about a half minute and caused numerous slides and subsidences of the loose ground. Many points of low-lying accumulative coastal relief forms: beaches at steep cliffs, spits, etc., disappeared.

The end of the spit, which cuts off Deep Bay, disappeared under water. The depth of the water to the north of the spit increased from 1.5 to 30 m. Apparently, the wave resulting from this slide reached the lighthouse situated to the east on Sisters Rock. According to the lighthouse attendant, a wave 2-2.5 m high rolled onto the little island 7 minutes after the earthquake; a second wave 0.25-0.5 m high moved in at a distance of 30 m from the first; the velocity of the waves was 10 knots.

A section of coast with a pier on Goose Spit which cuts off the entrance to Comox Harbor, subsided more than 0.5 m. Waves about a meter high were observed near the slide which occurred here.

Some sections subsided on Rebecca Spit, which cuts off Drew Harbor on the eastern coast of Quadra Island. According to a forest worker, a moment after the earthquake, the water level oscillated between the high and low tide marks at another place on this island. The water, which had been clear, became turbid. The fish did not bite for two weeks. A large tract of agricultural lands on Reid Island dropped 6-9 m.

In Alberni Bay opposite Franklin Creek, the water increased more than 30 m in depth. The underwater cable was broken and partially buried by detritus. In the words of an eyewitness, a roller 6-9 m high, arose on the surface of the water here. The roller then scattered along the axis of the bay and turned into small tidal waves, which were observed on its shores.

According to Hodgson (reference #2598), who carefully examined the epicenter zone of the earthquake, there were no real tsunami waves. Only these local waves arose, which were generated by collapses and suspension currents. A distinctive feature of this earthquake was the almost total absence of recurrent shocks.

(above from reference #415)

Based on dendrochronological analysis, tsunami deposits and aerial photographs Evans states: The 1946 Vancouver Island earthquake (M = 7.2) triggered a rock avalanche from the north face of Mount Colonel Foster, central Vancouver Island, British Columbia. The resultant displacement wave ran up a maximum vertical distance of 51 m on the opposite shore and the wave crest was about 29 m high when it spilled over the lip of the lake. Water displaced during the event destroyed forest in the upper reaches of the Elk River valley up to 3 km from Landslide Lake. (reference #9458) Note: runup these observations not included in historical database due to lack of instrumental recording or eyewitness accounts.