A series of three large earthquakes have struck off the coast of British Columbia, according to the United States Geological Survey.

There were no immediate reports of casualties or damage from the quakes.

The first struck just before 11 p.m. PT Sunday, around 190 km southwest of Port Hardy, a town on the northeast end of Vancouver Island.

The first quake, reported as a magnitude 6.5, was followed by another, with a magnitude of 6.8, around 40 minutes later.

The third quake was reported at magnitude 6.5 just before midnight, near the same area as the previous two.

Prelim M6.6 Earthquake Vancouver Island, Canada region Oct-22 05:39 UTC, updates <a href="https://t.co/6lqYoLl1L3">https://t.co/6lqYoLl1L3</a> —@USGSBigQuakes

Prelim M6.8 Earthquake Vancouver Island, Canada region Oct-22 06:16 UTC, updates <a href="https://t.co/pJAofbfief">https://t.co/pJAofbfief</a> —@USGSBigQuakes

Prelim M6.5 Earthquake Vancouver Island, Canada region Oct-22 06:22 UTC, updates <a href="https://t.co/d9rQfY9qqn">https://t.co/d9rQfY9qqn</a> —@USGSBigQuakes

Three in a row 'unusual'

CBC meteorologist and seismologist Johanna Wagstaffe said the earthquakes are a reminder that B.C. is in a "complicated" tectonic setting.

British Columbia is located on the Pacific Ring of Fire, an active seismic zone where thousands of mostly small earthquakes are recorded annually by sensors in the province.

Looking forward to more info tmrw but preliminary assessment this <a href="https://twitter.com/hashtag/earthquake?src=hash&ref_src=twsrc%5Etfw">#earthquake</a> not in our subduction zone (too shallow for one) & of strike-slip orientation (horizontal movement which is why no tsunami threat). We live in a complicated tectonic setting! —@JWagstaffe

Most of the quakes happen near the Cascadia subduction zone, an area where the Juan de Fuca and North American tectonic plates converge, stretching from Vancouver Island to northern California.

"If any one of these quakes had hit closer to land, there would have been devastating consequences," said Wagstaffe about the Sunday-Monday quakes.

"Three large ones in a row does seem unusual, and I'm sure scientists will be learning as much as they can over the next couple of days about the change in stresses just off our coast."

There were no immediate tsunami warnings following the earthquakes.

Earthquakes Canada also reported a magnitude 4.4 aftershock from the first quake before midnight, and three below magnitude 5.0 early Monday.

Multiple <a href="https://twitter.com/hashtag/earthquakes?src=hash&ref_src=twsrc%5Etfw">#earthquakes</a> felt in parts of <a href="https://twitter.com/hashtag/BC?src=hash&ref_src=twsrc%5Etfw">#BC</a>, but no reports of damage or injury. <br>NO Tsunami threat. RT <a href="https://twitter.com/USGSBigQuakes?ref_src=twsrc%5Etfw">@USGSBigQuakes</a>: Prelim M6.5 Earthquake Vancouver Island, Canada region Oct-22 06:22 UTC, updates <a href="https://t.co/hvAEGnVOmW">https://t.co/hvAEGnVOmW</a> —@EmergencyInfoBC

With files from Reuters and The Canadian Press