The U.S. Geological survey said the quake happened Tuesday at 7:29 p.m. about 140 miles southwest of Prince Rupert, or 400 miles north of Vancouver.
It began about 7 miles below the surface, the Canadian Broadcasting Corp. said.
There were no reports of injuries or damages in the sparsely populated, rugged area and no tsunami warning was issued, the report said.
Monday's quake wasn't far from a much larger quake that did trigger tsunami warnings Saturday night and Sunday.
The 7.7 earthquake was centered about 398 miles south of Juneau, Alaska, and was the strongest in Canada in more than 60 years.
Early Sunday, Hawaii responded to a tsunami warning and evacuated thousands of people from coastal areas, but they were allowed to return later in the day.
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