Roy L Hales/ Cortes Currents - The offshore region between Northern Vancouver Island and Haida Gwaii is one of the most seismically active regions in Canada. There have been more than 2,000 earthquakes during the last 4 to 5 years, and four of them measured more than 6 on the richer scale. While the 2.9 quake in Campbell River last February was smaller, it is a reminder that earthquakes happen here. In this morning’s broadcast Andrew Schaeffer, an Earthquake Seismologist with the Geological Survey of Canada, describes the network of seismic stations that have been erected to observe earthquakes on the West Coast
Cortes Currents contacted Schaffer last March because he installed and looks after the seismometer on Calvert Island, midway between North Vancouver Island and Bella Bella, but soon discovered there is a much larger story.
The seismometers at Mount Washington, Campbell River and Sayward are among the twenty installed on Vancouver Island.
There is another seismic station in Prince Rupert and a string of stations along the Douglas Channel and out to Banks Island. After that, there is a station in Bella Bella.
“Because it is a challenging area to work in, with very little in the way of communications, stations are fairly sparse on the inside north coast. They are more than adequate to detect magnitude four earthquakes, which is what the Canadian National Seismic Network is tasked to do. It is tasked to detect and alert magnitude four earthquakes anywhere is Canada. Those are the earthquakes that will have an impact. Those are the earthquakes that, if you are close to it, it could cause damage. Less than that could cause an unpleasant shaking, but they do not typically cause damage,” explained Schaffer.
TheGeological Survey of Canada is trying to understand the how, when and where of earthquakes.
“To do that, we need a better understanding of the small earthquakes. That’s where adding more stations along the coast comes in. We are not improving the protection of magnitude fours, but we are improving the detection and location of magnitudes twos and threes that allow us to paint a much clearer picture of where the earthquakes are happening and start to address questions like why? For example, there are 300 kilometres between Port Hardy and Bella Bella and we’ve cut that distance in half by installing a station on Calvert Island, which allows us to detect smaller earthquakes than we could before,” said Schaffer.
The seismic station on Calvert Island is extremely sensitive. For example, it records ground vibrations from the impact of waves hitting the beach and trees swaying in a breeze.
“When there is a local earthquake it is usually significantly higher amplitude than these features from wind and waves. Once there is an earthquake of a decent magnitude nearby, that will all of a sudden come out of this low level noise,” said Schaffer.
“The seismometer on Calvert Island has picked up every global earthquake of more than a magnitude five since it was installed. The most recent would have been those earthquakes in New Zealand off the Kermadec Trench. (See chart at top of page) It has picked up a very beautiful signal from all of those. Any earthquake around the world that is at least a 5 or so, 5½, possibly even 4 depending where it is: this seismometer will pick it up.”
