Overdue Mega-Quake Could
Sink Vancouver Island
Will an earthquake cause part of Vancouver Island to "break off and sink," or "split in two at Alberni Inlet?" No, says Dr Gerard Fryer of the Hawaii Institute of Geophysics and Planetology at the University of Hawaii, Honolulu.
" Mr Fryer is quoted as saying "If there is a big earthquake along your coast then the risk of a tsunami (tidal waves) is high and you'll probably only have ten minutes to evacuate. Figure out either the fastest way to get above an elevation of 20 metres (the top of a tall sand dune is fine) or to get a kilometer or so inland from the shoreline."
He said, "At least I can reassure you that Vancouver Island is not going to break apart in the next big earthquake. Rest assured too that a lot of people are trying to figure out just how Cascadia earthquakes happen so that they can advise you of the risks and maybe even give you a warning when one is about to occur."
Experts say that Most recorded earthquakes are caused by stress accumulation within the plates. In BC and offshore, earthquakes have occurred either within the Juan de Fucaor or North American plates. None have occurred along the junction where the two plates are actually in contact.
The apparent inactivity within the zone of contact between the plates suggests the plates are locked together and are accumulating strain.
This stress accumulation can result in a potentially very destructive type of quake, called a megathrust earthquake. Some experts believe this is exactly the type of scenario Vancouver Islanders should be preparing for.
In a big earthquake the seafloor offshore from Vancouver Island will be uplifted and the area along the coast will sink. Land sinking may only be a few meters, on the other hand we don't know that for sure. Some experts say that the way things appear, large areas could liquify or sink.
Does Mr Fryer speak from both sides of his mouth when he says that "a lot of people are trying to figure out just how Cascadia earthquakes happen so they can advise you of the risks"? And then he tells us that he can say that the island will not sink? If he has no concrete idea of how the cascadia affect will play out, how can he say that?
Would it be fair to say that any expert who says all we have to do is climb on top of a sand dune, of all things, could be downplaying the risks just a little bit? We have probably all heard the story about the man who built his house upon the sand!
Is it any wonder that vancouver island has no real earthquake plan to speak of, and continues to build it's public schools without earthquake safe design?
The Cascadia subduction zone is the major fault zone that extends offshore parallel to the Pacific coast from central Vancouver Island, Canada south to northwestern California.
Geologic evidence, primarily well-documented elevation changes in coastal marshes, is interpreted as indicating the repeated occurrence of great earthquakes along this zone which could measure anywhere from 9 to 13 on the richter scale. A level virtually unheard of, which could cause liquifaction, or island sinking.
There is good evidence that the Juan de Fuca and North America plates are currently locked together, causing strain to build up in the earth's crust. It is this squeezing of the crust that causes the 300 or so small earthquakes that are located in southwestern British Columbia each year, and the less-frequent (once per decade, on average, damaging crustal earthquakes (e.g., a magnitude 7.3 earthquake on central Vancouver Island in 1946). At some time in the future, these plates will snap loose, generating a huge offshore "subduction" earthquake.
These great quakes generate water waves, called tsunamis, capable of causing extreme damage to coastal areas on both sides of the Pacific. Using detailed tsunamis records from Japan, geologists have been able to date the last Cascadia earthquake as occurring on January 26, 1700.
The geologic record indicates intervals between these great earthquakes of 500 to 600 years.Many of these quakes occur at sea where they are not felt by populations that could be hit by tsunamis.
We could be quietly sleeping in our beds when we are wiped out, without ever having known about it. Or in a "best case scenario" where only certain areas are wiped out, some hypothesize that medical care would be very limited due to the fact that most physicians reside along beachfront properties which would most assuredly be destroyed.
By A. Longson