Earlier this month 400 tremors, which were not felt, were documented within a 24 hour period, with most of them located just south of Victoria. (Map from John Cassidy/Twitter)

Island moves four to five millimetres away from mainland

Southern Vancouver Island shifts due to tiny tremors

Tiny tremors in recent weeks are causing southern Vancouver Island to shift roughly four to five millimetres away from the Lower Mainland, says a local expert.

According to John Cassidy, an earthquake seismologist with Natural Resources Canada, the shift occurs when the Juan de Fuca plate sinks under the overlying North American plate, which Vancouver Island is on, causing them to lock together and store energy.

When the North American plate moves and releases some pressure in what is known as an episodic tremor and slip process, energy is released in the form of tiny tremors and causes the shift to the west. “As the ocean plate continues to be pushed towards us and it hits North America, it causes a buckling and a squeezing,” Cassidy said. “We have thousands and thousands of these little tiny tremors that nobody feels and they happen at the same time. When we record these tremors that we can easily locate, that’s the same time that Vancouver Island changes direction and moves to the west.”

RELATED: More than 150 tremors hit Vancouver Island in last 24 hours

Roughly 20 years ago, new GPS instruments were deployed and showed seismologists how the surface of the earth was moving.

What researchers found was that south Vancouver Island was slowly moving east roughly one centimetre towards the Lower Mainland each year. But as scientists began to process the data, they found it wasn’t moving smoothly.

Similar to a pin ball machine in which the ball bounces from one side of the machine to the other, scientists found southern Vancouver Island was also doing the same. Every 14 to 16 months over a two to three week period tiny tremors cause southern Vancouver Island to change direction and move roughly four to five millimetres to the west, away from the Lower Mainland, before continuing to move east again.

Cassidy said the information has helped researchers map out the parts of the subduction fault that are locked and where energy is being stored for future earthquakes. It allows them to estimate ground shaking, but doesn’t allow them to predict when an earthquake could take place.

Northern Vancouver Island will also go through a similar process within the next couple of months, changing directions and moving to the west, before continuing to move east.

While Cassidy said the shift is not out of the ordinary, it is a reminder to Island residents that they live in an active earthquake zone.

“We’re just a little bit farther from Vancouver for a few weeks,” he joked, adding the shift has also been seen in other parts of the world as well.

“It’s been scientifically useful, but for all of us, it’s a good reminder that this is an active earthquake zone.”


Like us on Facebook and follow us on Twitter

kendra.wong@goldstreamgazette.com

Just Posted

Ladysmith Interact club students inspired and inspiring

Ladysmith Secondary School group making a difference in their community

IIO doesn’t recommend charges after motorcyclist death in Mill Bay

An off-duty VicPD officer was involved in the crash

New wind warning for most of Vancouver Island

Forecasters are calling for strong winds up to 90km/h for some areas

Mount Washington opening for winter season this weekend

The resort’s original opening day was delayed due to lack of snow

VIDEO: Kitten rescued from under school bus in Duncan

School staff have affectionately called kitten “Axle”

VIDEO: Royals reveal the images on their Christmas cards

Prince William and his wife Kate are shown outside in casual clothes, their three young children in tow

Media, robotics, Indigenous studies coming to B.C. Grade 12 classrooms in 2019-20

Provincial tests are also being changed for students in Grade 10 to 12, the Education Ministry said

ICBC to apply for 6.3% hike to basic insurance rates

Crown Corporation said it will be submitting its next basic rate application to the British Columbia Utilities Commission Friday

Stranded B.C. trucker writes final wishes before being rescued 3 days later

‘I was just praying someone would come along’

Canfor Corp. extending temporary curtailment of sawmills in B.C.; cutting hours

Vancouver-based company says the decision is due to declining lumber prices, high log costs and log supply constraints

Canada’s prospective world junior team members await final roster decisions

Thirty-four players were invited to the national junior selection camp

Woman guilty of impaired driving in death of Vancouver Island pedestrian

Man in his 70s killed in 2016 Courtenay multi-vehicle incident

Rash of bomb threats a learning opportunity for response capacity, Goodale

Thursday’s wave of bomb threats swept across communities on both sides of the Canada-U.S. border

Windstorm topples tree onto townhouse in Nanaimo

Heavy winds have thousands of B.C. Hydro customers without power

Most Read