Earth-shaking Discovery
A Simon Fraser University researcher has come up with an earth-shaking theory about where seismic activity is likely to pop up on the West Coast.
 Earthquake specialist Dr. Andrew Calvert analyzed seismic images of the Juan de Fuca plate, which runs from northern California to Vancouver Island, and is being pushed under the neighbouring North American plate.
Dr. Calvert realized for the first time that there was a region of rock trapped between the two plates as they grind together, creating two separate faults on top of each other. This obstacle – around 100 km wide and 5 km thick – causes the Juan de Fuca plate to sharply change the angle at which it descends below the North American plate.
When Dr. Calvert compared this finding to data on earthquakes, he found that the two dips the Juan de Fuca plate makes on either side of the trapped rock correspond to the distribution of earthquakes in the Juan de Fuca plate around Vancouver Island.
It seems these steeper dips must have something to do with the seismic activity, a discovery that may help scientists pin-point exactly where a quake may strike, as well as how severe it will be.
Dr. Calvert says these findings show a need for more research into how tectonic plates behave. “We assumed the plate boundary was a simple structure. But now we know that it’s more complex,” he says. “The more we look at the process, the more complex it seems to be.”
Contact:
Dr. Andrew Calvert
Simon Fraser University
Tel. : (604) 291-5511
E-mail: acalvert@sfu.ca
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