Nearly 400 earthquakes shook various regions of Canada last month, but only a handful were noticeableB次元官网网址攁t least to humans.
B次元官网网址淚t is a pretty typical month,B次元官网网址� said John Cassidy, an earthquake seismologist with Natural Resources Canada. Cassidy works with the national earthquake hazard project based in Victoria.
The west coast of Canada is one of the most active areas for earthquakes, with approximately 80 percent of CanadaB次元官网网址檚 earthquakes happening along the Pacific Coast.
Even May 1B次元官网网址�2 before the Alberni Valley B次元官网网址 went to press there had been 22 earthquakes recorded, including three west of Tofino and Port Hardy, and another south of Port Renfrew on Vancouver Island. A magnitude 3.6 earthquake near Mount Vernon, Wash., was felt in the early-morning hours of May 1. The quake was 80 kilometres away from Victoria and nearly equidistant with Seattle and Vancouver.
B次元官网网址淲e see 4,000 to 5,000 earthquakes located across Canada each year. ThereB次元官网网址檚 undoubtedly more than that because those are the located ones,B次元官网网址� said Cassidy. Earthquakes that are picked up by seismographs are usually magnitude 2.0 to 2.5 or larger.
388 across during the past month. A typical pattern with ~80% of the earthquakes on/near the active plate boundaries of western Canada. The largest was M5.3 (offshore Vancouver Island) and only a few were felt this month.
B次元官网网址� John Cassidy (@earthquakeguy)
Details:
B次元官网网址淎lmost all of those are tiny and not felt.B次元官网网址�
There are typically three dozen earthquakes felt across Canada every year, and that number has remained constant for the past two decades.
Most of the earthquakes that occur on the west coast do so because tectonic plates underneath land and sea move and shift along active fault lines. Tectonic plates are slabs of solid rock, some larger than a continent, that shift slowly and change the topography of Earth.
In southwestern B.C., for instance, the Explorer and Juan de Fuca plates are B次元官网网址渟hiftingB次元官网网址� underneath another called the North American Plate. TheyB次元官网网址檙e moving somewhere between two and four centimetres per year, according to Cassidy.
Did you feel shaking in northwest and southwest at 4:16 this morning? Many people did.
B次元官网网址� John Cassidy (@earthquakeguy)
That was a M3.6 earthquake near Mount Vernon - nearly midway between Seattle (90 km), Victoria (80 km) and Vancouver (110 km).
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Another natural event that has been occurring onB次元官网网址攐r perhaps more suitably B次元官网网址榰nderB次元官网网址橞次元官网网址擵ancouver Island lately is something called episodic tremor and slip. TheyB次元官网网址檙e likened to ground vibrations, similar to windstorms.
More than 6,000 of these events were recorded between March 20 and April 7. They are not felt, and they happen every 14 months or so, according to Cassidy.
These B次元官网网址淓TSB次元官网网址� started in September 2021 in the southern Vancouver Island and Northern Washington State regions, according to the Pacific Northwest Seismic Network.
The curious thing, says Cassidy, is very little is known about the correlation between earthquakes and episodic tremors. B次元官网网址淲e donB次元官网网址檛 think thereB次元官网网址檚 any link,B次元官网网址� he said, B次元官网网址渂ut itB次元官网网址檚 something weB次元官网网址檙e still actively working on.B次元官网网址�
Episodic tremors were discovered about 20 years ago here on Vancouver Island. They have been found to run along the subduction zone, which follows the coast line and is approximately 100 kilometres wide. Similar episodic tremors and slip are happening at subduction zones around the world, he added.
Only 67 tiny ETS tremors (not felt) on southern today - perhaps ETS is winding down! Nearly 6000 tremors have occurred here since March 20th.
B次元官网网址� John Cassidy (@earthquakeguy)
More on Episodic Tremor and Slip (ETS):
Cassidy said the number of earthquakes recorded in April, coupled with the number of episodic tremors, is a good reminder that we live in a seismically active zone, but said there is nothing out of character. B次元官网网址淭heyB次元官网网址檙e both typical patterns. Nothing unusual,B次元官网网址� he said.
There are few places that donB次元官网网址檛 experience earthquakes: one would have to move to the prairies for that, said Cassidy. Saskatchewan and Manitoba, as well as parts of the country under the Canadian Shield (Laurentian Plateau) rarely feel earthquakes because they are farthest away from tectonic plate movement.
We feel them more on the west coast because Vancouver Island is situated within an earthquake zone.
B次元官网网址淓arthquakes are happening each and every day,B次元官网网址� he said. Some of the damaging earthquakes happen B次元官网网址渆very decade or two.B次元官网网址�
Devastating earthquakes, such as one that hit the Comox Valley area in 1946, fade from memory because they donB次元官网网址檛 happen all the time. B次元官网网址淚tB次元官网网址檚 easy to forget about those events but they do happen and they will happen. ItB次元官网网址檚 good to take advantage of the reminder that we live in an area that has seen large earthquakes,B次元官网网址� Cassidy said.
He said there are websites such as EmergencyInfoBC or Shakeout BC that have information on how to prepare in the event of an earthquake. He suggested keeping a flashlight and slippers or shoes by the bed, so you have a way to see and protect your feet from debris on the floor following a serious earthquake.
B次元官网网址淭hatB次元官网网址檚 our message, is not to be afraid or worried but to be prepared.B次元官网网址�
Earthquakes Canada uses the information its seismologists collect to help builders and emergency managers know what to expect for future events.
B次元官网网址淭hatB次元官网网址檚 really the goal of all the work that we do is to minimize the impact of earthquakes we may have in the future.B次元官网网址�
susie.quinn@albernivalleynews.com
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