Experts say a "swarm" of small earthquakes off the northwest coast of Vancouver Island are part of the normal seismic activity in the area, and they could continue for several more days.

A 4.0 magnitude earthquake that struck just after midnight on Tuesday morning was the eighth small quake with a magnitude between 3.8 and 4.7 to strike the region since April 22.

Earthquakes Canada notice: There is a light swarm of earthquakes occurring offshore of Vancouver Island. The largest event was a magnitude 4.7 earthquake on Apr 22 and seven other earthquakes in the magnitude 4 range on Apr 27. These earthquakes are too far from land to be felt. Source: Natural Resources Canada

Pacific Geoscience Centre Seismologist Gary Rogers said the activity is focused along a 20-kilometre stretch along an area called the Raveer Delwood Fault, located about 200 kilometres offshore.

"In the very thin crust that we have out there off our west coast of Vancouver Island, it often fractures in a series of small earthquakes, usually about this size being the maximum."

Rogers said more small earthquakes are expected in the area over the next week.

"They often go on for days. There's been a lot of smaller ones, so eventually they'll wind down, but typically, what we've seen in the past is that most of these swarms last a few days to a week or so."

A similar but more powerful swarm that struck the same area in August 2008 included a magnitude 5.2 quake.

Experts have been warning a major earthquake hits B.C. every 500 years, and the last one was in 1700. But they said the swarm of small earthquake activity does not indicate a larger earthquake is more likely in the short term.

The last significant quake to rattle the West Coast was a magnitude 6.5 tremor centered that struck about 50 kilometres off the west coast of the island in September of 2011, swaying high-rises as far away as Vancouver, Kelowna and Seattle.