Author Topic: Tsunami Warning in BC  (Read 197 times)

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Offline TimG

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Re: Tsunami Warning in BC
« on: January 23, 2018, 06:24:12 pm »
I used to believe that about Vancouver Island protecting Metro Van but came to find out a little while ago that it's not true. 

In fact, the warnings today actually included Vancouver.

Although direct evidence of tsunami impacts is lacking, a computer model  showing the propagation of tsunami waves from a great earthquake releasing 500 years of accumulated strain on the Cascadia subduction zone has recently been developed by a group of oceanographers at the Institute of Ocean Sciences in Sidney, British Columbia. Their simulation model predicts that a great earthquake at the Cascadia subduction zone will generate tsunami waves about 510 m high on the outer coast (Fig. 6). These large waves gradually diminish in height as they move through Juan de Fuca Strait and the narrows between the San Juan and Gulf Islands. The leading edge of the first wave is forecast to reach Boundary Bay on the southern foreshore of the Fraser River delta about 2 hours and 5 minutes after the earthquake. Because Boundary Bay is oriented at right angles to the direction of wave travel, this wave grows to a height of about 1 metre. The second wave, which is approximately the same size as the first, arrives at about three hours and 30 minutes. A third, slightly smaller, wave arrives at about five hours. By six hours this wave grows to almost 2 metres in height. Unlike Boundary Bay, the western foreshore of the Fraser delta lies parallel to the direction of wave travel, and the maximum wave heights on this foreshore are forecast to be much smaller (less than 0.5 metre).
So we have a computer model but absolutely no historical evidence of tsunamis. This is in contrast with Vancouver Island where historical evidence is plentiful (including first nations oral history). The computer models may be enough to justify spending money to shore up Richmond's dikes but I am not going to worry.