VANCOUVER -- Sirens wailed on the Alaska Peninsula Tuesday night after a massive 7.8 magnitude earthquake struck about 100 kilometres off the coast.

It happened around 11:30 p.m. and triggered a tsunami warning, forcing people to evacuate buildings and move to higher ground. Luckily, a wave never came.

Brett Gilley, an associate professor with UBC’s earth sciences department says that area of the world is a "subduction zone."

"That's a place where the plates are coming together so the Pacific plate is trying to pass underneath Alaska,” he said, adding that it’s common to see about three powerful tremors a year.

While it was a strong quake, Joseph Farrugia from Natural Resources Canada says it wasn’t enough to impact B.C.

"This earthquake was far enough away, we didn’t feel any shaking and we weren’t at any risk of any tsunami," Farrugia said.

Hours later, a smaller tremor was detected off the coast of Tofino. Initial reports from Earthquakes Canada measured the tremor at 5.1 magnitude, while the U.S. Geological Survey recorded the earthquake as 5.4 magnitude. The USGS first reported the earthquake as 6.2 but later downgraded it.

Gilley says there was no tsunami warning issued because it was a different type of quake.

"That’s in an area of extension so the plates are pulling apart, we tend to get a lot of smaller earthquakes and that one was far enough away from Vancouver Island that I’m not really sure how many people felt it."

The Pacific Northwest is a hot spot of seismic activity, and for years, experts have been warning B.C. residents to prepare for "the big one."

"We had a big one about 300 years ago so we’re, quote, due, but it could be 1,000 years yet," said Gilley.

Early warning system

For years, there has been an early warning system in development. Starting in 2016, Ocean Networks Canada, working with the University of Victoria, began placing a number of sensors both underwater and on Vancouver Island to track seismic activity in real time.

The system has moved into the commissioning phase, where ONC is working with agencies such as the Canada Line and Fortis BC in trialing automatic shutdown alerts if a major earthquake is detected. For example, shutting off gas supplies to certain areas, alerting hospitals to pause surgeries and stopping the Skytrain from running.

Teron Moore, the public safety program manager for Ocean Networks Canada, says an early warning system would only give a maximum two minute warning before the shaking starts.

"The time can be anywhere between zero seconds of warning and about two minutes. That’s kind of on the maximum end and that’s really related to how far the earthquake is to your location," Moore said. "With earthquake early warning, you’re dealing with seconds, not hours or days."

The current phase of testing is due to end in March 2021. Moore says after that, it will be up to government bodies to decide how to push alerts into the public space, like to people’s phones.

"You could also think about sirens, or PA systems in schools or officers, computer systems and computer screens could alert people to an incoming earthquake," Moore said.

But he stressed that even with an early warning system, there’s not much time, so people need to be prepared.

"Think about what you can do before the earthquake, even today, to make your house a little bit safer, make your workplace safer."