Quake Registers 6.1 Off the Northern Coast of Vancouver Island

A violent earthquake shook the ocean floor off the northwest coast of Vancouver Island, 191 kilometres west of Port Alice, B.C., early Thursday in the latest in a swarm of tremors this week.

Natural Resources Canada's Earthquakes Canada section initially recorded the tremor measuring a magnitude 6.1 at 5:37 a.m. PT but has downgraded it to a magnitude 5.5, according to its website. It said the quake was "too small to cause a tsunami."

The U.S. Geological Survey, which first measured the quake as magnitude 6.1 with a depth of 10 kilometres, has downgraded it to a magnitude 5.8, according to its website.

"There have been no felt reports, but this earthquake may have been felt mildly on Northern Vancouver Island," Earthquakes Canada's website said.

'Eventually we will have larger earthquakes on land because they are all part of the system.'
— Garry Rogers, earthquake scientistThe quake Thursday is the latest in a swarm of tremors rocking the ocean floor off the west coast of Vancouver Island. A magnitude-5 quake struck the ocean floor west of Vancouver Island at 1:17 p.m. PT on Wednesday. There were no reports of damage or risk of a tsunami.

In total, there have been 18 quakes in the same region this week.

Earthquake scientist Garry Rogers with the Geological Survey of Canada said Thursday that swarm activity happens several times a year in the area — an indication that the tectonic plates are moving.

"Swarm activity is common for that area … where new oceanic material is being created," Rogers told CBC News in a telephone interivew.

"[It's] an active volcanic region offshore under the water [and] has lots of small earthquakes. Typically they occur like this in swarm activity," he said.

More quakes are expected in the next few days and they could include an even larger one, Rogers said.

"They're all connected to land and eventually we will have larger earthquakes on land because they are all part of the system."