I monitored a discussion about the possibility of a tsunami hitting the east coast of Vancouver Island at a recent meeting in the Cowichan Valley Regional District with great interest.
The district is considering applying for a $400,000 provincial grant to assess the risk of tsunamis to both the western and eastern shorelines of the CVRD.
CVRD chair Kate Segall said at a committee of the whole meeting on March 26, where the subject arose, that she had been taught that the threat of a tsunami hitting the east coast of the district in the Salish Sea was minimal, if not non-existent.
But Ryan Wainwright, the senior manager of Emergency Management Cowichan, said tsunami science has progressed over time and it has been determined that near-shore earthquakes and other events do have the possibility of generating tsunamis on Vancouver Island’s east coast.
The main concern for most people in the region when it comes to earthquakes is where the Juan de Fuca tectonic plate meets the North American plate at a subduction zone in the waters offshore of Tofino and Ucluelet, where the “Big One”, a huge earthquake registering 9.0 magnitude or more, is expected anytime from right this moment to 300 years from now.
Many here in the Cowichan Valley and others along the east coast of Vancouver Island have long believed that they would be mostly insulated from tsunamis if and when that cataclysm happens as there is almost 100 kilometres of land between us and the earthquake that would protect us, with those on the west coast taking the brunt of it.
But Wainwright dispelled that myth and said that the east coast could be just as vulnerable as anywhere else, and that’s why local emergency services want to study and assess the risks of tsunamis in the region.
In fact, there have been three earthquakes that have struck in the Vancouver Island area over the last few weeks that were closer to the Salish Sea than many realize, and they were not directly connected to where the Juan de Fuca tectonic plate meets the North American plate.
On Feb. 21, a 5.1-magnitude earthquake hit near the Sunshine Coast, followed by a 4.5 earthquake on March 3 about 10 kilometres off Orcas, Wash. and a 3.9 one occurred about 58 kilometres south-southeast of Victoria on March 5.
Just nine years ago, Canadian and American seismologists confirmed the existence of a previously unknown earthquake fault zone just five kilometres south of Victoria, called the Devil’s Mountain Fault Zone.
The zone is actually made up of a series of faults that run from Washington state to Victoria.
The Devil’s Mountain Fault Zone lies entirely on the North American plate, which usually generates smaller, shallower crustal earthquakes, but they could potentially be as high as a 7.5-magnitude shaker, which could do a significant amount of damage to the Cowichan Valley if (or when) they occur.
Also, as I mentioned in a column I wrote a number of years ago, of equal or greater concern to Valley residents should be a report released by BC Hydro and the Geographical Survey of Canada in 2003.
That report envisions a towering wave the size of a six-storey building rising up out of the Salish Sea and rolling west, slamming into the Gulf Islands and the east coast of Vancouver Island mere minutes after a major earthquake strikes the area.
Apparently, between 17 million and 20-million tonnes of sediment build up at the mouth of the Fraser River in the Salish Sea every year.
The study concluded that it’s possible that a major earthquake in the region could see a significant underwater landslide of the ever-accumulating sediment that could cause huge tsunami waves that would quickly come our way.
That would play havoc with shoreline communities in this area, and the water could, theoretically, reach much higher in a worse-case scenario.
There are other experts that have since concluded that such an event is highly unlikely, but they haven’t dismissed it outright.
The fact is that we live in a highly seismically active area, and I hope that the CVRD gets the provincial grant to carry out its study.
I'd certainly like to know what we should be prepared for.
