Three earthquakes felt across Greater Victoria since Feb. 21 is more frequent than normal but not something a local seismologist sees as a precursor to a megaquake that threatens to reduce buildings to rubble.

On Feb. 21, a 5.1-magnitude earthquake hit near the Sunshine Coast, followed by a 4.5 earthquake on March 3 about 10 kilometres off Orcas, Wash. and a 3.9 about 58 kilometres south-southeast of Victoria on March 5.

The shakes have left the 'Big One' on many Greater Victorian minds – a megaquake on the boundary between the Juan de Fuca and North America plates. The last megaquake hit Vancouver Island in January 1700 and is predicted to occur in cycles of between 300 and 700 years.

"There's no deeper meaning," says Edwin Nissen, a professor and Canada research chair in seismology at UVic’s School of Earth and Ocean Sciences, referencing the recent slew of quakes.  "I would say every year, there's one or two earthquakes on average that are large enough and close enough to Victoria that people will feel some shaking. And we just happen to have had two within two weeks. And they're not close enough together."

Two quakes were about 100 kilometres apart and "too far" to be directly related, he said. "They're also in the North American crust, so they're actually nothing to do with the megathrust, the offshore force."

Unfortunately, there are no precursor events that seismologists can look out for to give a warning that a megathrust is on its way, he said. Nissen describes these precursors as the "holy grail of seismology" and researchers are "looking hard" for them. The depth at which faults occur also makes this challenging.

Only a small proportion of megaquakes have foreshocks – smaller earthquakes just before they happen – and these are generally not recognized as such until after the big quake happens, Nissen explained.

He likens a megaquake to blowing up a balloon. "You know it's going to pop. Can you predict at what time it's going to burst? Is it going to be a minute? Two minutes?" It's the same with a megaquake, it's going to happen eventually and every year it gets a little bit closer as the fault is stressed a little bit more, he said.

The last 'Big One' in 1700 had an estimated magnitude of 8.7 and occurred along the Cascadia Subducton Zone, a fault line that stretches from roughly 100 kilometres off the west coast of Vancouver Island about 1,000 kilometres to Northern California.

It generated a huge tsunami that devastated many First Nation communities.

While predicted to hit in cycles between 300 and 700 years, it is not the only type of earthquake to worry about, Nissen explained.

Where the crust of the Juan de Fuca Plate is being pushed down underneath North America, you can also get "deeper earthquakes, which are actually kind of below Victoria, below Vancouver, Puget Sound," he said. 

"They can be quite large, not anywhere near as big as the megathrust earthquakes, but they can be sort of magnitude seven or so. They can be quite damaging, but because they're so deep, they tend to not be really devastating."

He cited the most recent one in 2001 – a magnitude seven in Washington state. "It caused a bit of damage in Seattle, but I think only one or two people were killed." He said these types happen every two or three decades and seem to affect Washington State more than Vancouver Island.

Relevant to what's happened in the last couple of weeks are smaller earthquakes at crustal faults, in the crust of the North American plate. "They can also reach about magnitude seven, so quite big. The reason that they could be dangerous is that they are close to where we live."

The megaquake, on the other hand, has a 1000-kilometre-long fault that has to rupture, and the seismic waves – what we feel as shaking – would last for a few minutes, Nissen estimates.

"It would be quite the experience," he said.

For communities on the West Coast – Nissen referenced Tofino, Port Renfrew, and Ucluelet â€“ a tsunami wave is probably the "bigger danger" if a megaquake were to happen. These communities would probably get hit with a wave within minutes – possibly up to 10 – after the quake.

Victoria is much safer from a tsunami as models suggest it might take an hour or so for the wave to reach it and be smaller in size by that time, giving Greater Victorians "plenty of time" to get to safer, higher ground – Nissen recommends about two to three metres above sea level to be safe.

In Victoria, the greatest risk is from the ground shaking, he said.

While the last slew of quakes is not a signal of danger, Nissen said it's important to use them as a "welcome reminder that we do live in a plate boundary zone."

"People should think about earthquakes, prepare for earthquakes, know what to do in an earthquake," he said.

That includes ducking to cover, and holding on to shelter while covering your head and neck if you feel the ground shaking. If you're on the coast, get to higher ground calmly. "You don't need to rush, but just calmly walk to higher ground immediately," he said.

"Things falling off the walls are probably the biggest danger to a lot of people. And bear in mind that a big earthquake could make a lot of homes unlivable, so have an emergency kit. If you do have to leave your home, then you have food and water and things for a few days; clothes, medications, your important paperwork, the kind of things you would need to prepare for flooding, wildfires or all sorts of other hazards."

More tips can be found on the government of B.C.'s  page.