Disaster

Observing Earthquakes off the West Coast

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 magnitude 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 observe earthquakes off the West Coast

Image: Andrew Schaeffer, an Earthquake Seismologist with the Geological Survey of Canada.

Seismic Stations

Cortes Currents contacted Schaffer last March because he installed and looks after the seismometer on Calvert Island, but soon discovered there is a much larger story.  

The seismometers at Mount Washington, Campbell River, Quadra Island 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 4 earthquakes, which is what the Canadian National Seismic Network is tasked to do. It is tasked to detect and alert magnitude 4 earthquakes anywhere in 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. 

Map showing seismic stations (triangles in map above) in Northern Vancouver island and the West Coast (HAKB is Calvert Island) – courtesy the Geologic Survey of Canada.

How? When? And Where?

The Geological 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 against magnitude 4s, but we are improving the detection and location of magnitudes 2s and 3s. This allows us to paint a much clearer picture of where the earthquakes are happening and start to address questions like why?” said Schaffer.

“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.”

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.

Laying the foundation on Calvert Island – courtesy Andrew Schaeffer

Detecting earthquakes

“When there is a local earthquake it is usually significantly higher amplitude than these features from wind and waves,” said Schaeffer.

(Compare the waves from New Zealand’s earthquake to more mundane vibrations in the graph at the top of this page.)

“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.” 

Building the seismic station on Calvert Island (Fall of 2020) – courtesy Andrew Schaffer,

The seismic station at Calvert Island

Schaeffer works out of the Pacific Geoscience Centre in Sidney, BC.  

In the podcast above he explains how Calvert Island’s seismometer came into being through a collaboration between the Hakai Institute and Geological Survey of Canada. 

When 10 million cubic metres of rock plunged into Elliot Creek, sending a tidal wave into Bute Inlet last November, they sent out a low frequency signal resembling that of a 4.9 earthquake. This was recorded by the newly installed seismology station on Calvert Island. 

The completed seismic station – courtesy Andrew Schaeffer

Links of Interest:

Top photo credit: readings from the Calvert Island seismic station during the first hour that the New Zealand quake struck on March 4, 2021

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