Here on the West Coast we hear a lot about tsunamis.
As we know from recent events in Japan and southeast Asia, tsunamis can be incredibly
destructive.
So, what exactly are tsunamis and where do they come from?
A tsunami is what we refer to as a body wave.
It affects the entire water column in an ocean or a lake.
It is essentially is a wave phenomenon in that energy is propagated away from a source.
I kind of, because they've been so destructive, refer to them as stealth killers.
The seismic ones generated by earthquakes when you displace the bottom.
Off Sumatra in 2004, that huge tsunami that was generated there, was displacements of
five to ten metres in the bottom where suddenly the bottom goes up on one side and down on
the other and all that water, two thousand metres of water, is displaced.
Huge waves are generated.
So that's earthquake generated tsunamis, seismically generated tsunamis.
They happen everywhere in the world.
The other kind are landslide generated tsunamis.
So a failure of the coast line or some kind of big slump that fails and it pushes the
water ahead of it as it fails or a mountain falls into the water.
But about eighty percent of the big tsunamis in the world are generated in the Pacific
Ocean and the reason that tsunamis occur in these environments is that's where big earthquakes
occur, along the Pacific Ring of Fire.
It's called that because these earthquakes are also associated with active volcanoes.
We get these very explosive, fiery eruptions that occur because these plates are in contact
with one another and generating the forces that can create both earthquakes and volcanic
eruptions.
The speed of a tsunami is basically set by the depth of the ocean so if we use an average
depth of the ocean about five kilometres it's basically the speed of a jet.
So that's 700-800 kilometres per hour.
You're on an aircraft coming from Japan for example towards Canada during the 2011 Japanese
tsunami your jet plane would just be able to keep up with that wave as it crossed the
ocean.
It took it nine hours and fifty-seven minutes to get to Bamfield on the west coast of Vancouver
Island.
So this massive wave can move at the speed of a jet!
What are the odds of a tsunami landing here?
And if one does, what should we do?
The likelihood of a tsunami coming to Vancouver Island is actually very good.
We live in a very seismically active region and so we are
at a high risk of tsunamis.
So any Pacific based earthquake, and large Pacific based
earthquake could cause a tsunami which could impact British Columbia's Pacific coast.
We have developed with Rick Thomson very very precise sensors on the bottom of the ocean
that actually measure the actual pressure of the water which is really equivalent to
the height and we can precisely measure to sub-millimeter detail in 3 kilometers of water
how high that wave is.
And so with those sensors we can then begin to use models to predict the speed and direction
and the height of the wave that will impact our coast.
If there is a mega thrust earthquake off our coast we will have a major tsunami and we
want to be able to provide much more direct warning.
Now we wouldn't be doing this directly, we have to work with our emergency management
teams here in British Columbia but that's the direction we want to go in.
The information and data that's collected from Ocean Networks Canada helps emergency
managers to understand what kind of tsunami might be coming in at any given time.
We have the ability with the technology we have, to do an early detection of an earthquake
when it first hits.
We may be able to give places in Vancouver and Victoria a thirty to forty second warning
of major ground shaking hitting.
That's a lot.
People say well that's not very much but it can turn off a valve, it can stop trains,
it can set off an alarm in schools.
So there's many things we can do with that.
So we're working with a team of people in British Columbia over a five year time period
to see if we can implement something like that.
I think the most important thing about tsunamis is understanding your risks, where you live,
where you work and where you play.
So if you're travelling to an area that has tsunami risks to understand that there is
a tsunami risk and then to understand what you would take, what actions you would take
to keep yourself safe in the event of a tsunami.
You're walking the beaches in Tofino and there is a big earthquake, don't even wait for any
warning just go to higher ground because you're going to have about half an hour, at most
three quarters of an hour before that tsunami hits and it's going to be big on the outer
coast.
Today we had a chance to learn more about tsunamis.
Thanks to the team at Ocean Networks Canada and thanks to you for being part of our ongoing
explorations here at Ocean Alive!