Vancouver Island was created as a result of the earth rising due to the pressure of the Juan de Fuca plate and the Explorer Plate slowly travelling under the North American plate in the Cascadia Subduction Zone. For the same reason, this is one of the most earthquake-prone areas in Canada.
Large ‘megathrust’ earthquakes take place in the vicinity of Vancouver Island approximately every 500 years. Scientists believe that quakes of this type took place around 600 BC, 170 BC, 400 AD, 810 AD, 1310 AD, and in 1700AD.
The most recent megathrust quake took place on January 26, 1700 at 9 p.m. This time has been pinpointed due to the very accurate timekeeping of the Japanese, who reported an ‘orphan’ tsunami (a tsunami without a quake) that took place the following day.
The 1700 earthquake was estimated to have measured about 9.0 on the Richter scale, and struck near the Canada border with Washington State.
Many First Nations’ oral histories tell of this quake. The Nuu-chah-nulth on the West Coast of Vancouver Island have stories that tell of a great quake that happened before the first white men came. Some Coast Salish tribes have stories that tell of a violent shaking of the earth that went on for 20 hours (this likely includes aftershocks), made houses fall down, and people on land get seasick.
A Makah storey tells of great flooding which covered the land up to the trees for four days. Other communities tell of sand that shook until it swallowed things up.
The effects of more recent earthquakes have been felt on Northern Vancouver Island.
A 7.0 quake centered in the area near the Estevan Point Light Station woke up people around the island at 12:41 a.m. on December 16, 1918, but did not cause much damage.
A 7.3 quake in the mid-island area at 10:13 a.m. on June 23, 1946, knocked down 75 per cent of the chimneys in the Campbell River/Comox area, and caused a soil failure that ripped apart the highway near Sayward. It has the distinction of causing the most recorded damage of any quake on the island in historic times.
On August 21, 1949, at 8:01 p.m. a strong 8.1 quake struck in Haida Gwaii which reportedly knocked over cows near its epicentre, but this quake was not felt strongly on the North Island.
A 9.2 quake in Alaska on March 27, 1964 caused a tsunami that hit many West Coast communities. Most people are aware of the damage that happened in Port Alberni, but a number of more northern communities also felt its effects.
Hot Springs Cove and Zeballos both reported a rising tide that would not stop rising. The water kept coming until almost every building was knocked off its foundations, and several floated some distance.
The Zeballos Iron Mine, which was on higher ground, served as a makeshift shelter. Crew buses transported women and children from the village to the mine camp, and cooks provided hot food for the refugees.
Local accounts told of massive churning of waters around Tahsis Narrows killing thousands of bottom fish, which were rapidly forced to the surface where their swim bladders exploded.
In Port Alice an airplane dock, mail wharf, and oil float were all damaged.
The coastal float camps were largely able to ride out the tsunami. The tsunami occurred at a low tide, and damage would have been much greater if the tide was higher at the time.
Another more local tsunami took place in Knight Inlet around 1600 BC. First Nations oral history tells of a massive landslide on the South side of the channel, on the side of a mountain the First Nations knew as “Tohu.”
A landslide caused three to four million cubic metres of rock to fall into the inlet to a depth of 500 metres. This caused a tsunami wave somewhere between 3 and 10 metres in height that travelled across the narrow inlet in less than a minute, sweeping away the unsuspecting village of Kwalate.
The village was believed to have been home to more than 100 people, with four chiefs, who were all lost in this tragic event. A number of the victims were recovered and were laid to rest near the entrance to Simoom Sound, and pictographs of four coppers etched into the nearby rock are believed to commemorate the event.
Archeological excavations found evidence of the old village site, including middens and firepits under one metre of overburden. Covering the village site were tsunami deposits one to five centimetres deep, mostly of sand. The village was abandoned after this event, and never recolonized. Today the event is much studied by geologists, looking at the potential of tsunamis from above and from underground landslides.