Scientists in Victoria have successfully placed the first offshore early warning earthquake sensor along the seabed off Vancouver Island.

It will be part of a network of seismic sensors at the Cascadian subduction zone, a fault that is expected to produce a severely damaging earthquake within the next 50 years.

"We are the first really in the world to do this offshore," said Kate Moran, president of Ocean Networks Canada, based at the University of Victoria.

"It's very expensive, but it's very important to get them closer to the fault."

During a recent expedition, scientists installed three underwater sensors along the fault at depths of more than 800 metres. One was hooked up to start providing data.

The network will eventually include eight sensors offshore, along with many more sensors on land on Vancouver Island.

The sensors are being placed offshore because it puts them closer to the fault zone. (Ocean Networks Canada)

Once the network is complete it will provide up to 90 seconds of warning when a major earthquake strikes. That could be enough time to help people to take cover and to protect critical infrastructure.

"The denser the network, the more information we have to get a precise location ... and time before the secondary wave, the shaking wave, arrives in Victoria or Vancouver or in places of dense populations," Moran said.

Attaching delicate sensors to the seabed along the Cascadia fault, about 80 kilometres off the B.C. coast is no easy feat. The expedition involved nearly 150 people, three ships and three remotely operated vehicles.

"The sensor had to be placed in a glass sphere so it could withstand the pressure, so it's an incredibly complicated approach to actually getting them offshore and having them work," Moran said.

Cables also had to be carefully laid all the way back to an onshore monitoring station on Vancouver Island.

"The data will flow to our shore station in Port Alberni and then directly from there into our database at the University of Victoria campus," said Martin Scherwath, staff scientist with Ocean Networks Canada.

Kate Moran is president and CEO for Ocean Networks Canada, based at the University of Victoria. (Megan Thomas/CBC)

Data has started coming in from the first sensor that is up and running. Scientists have already been able to analyze information from recent minor earthquakes, Scherwath said.

But the ability to provide warning ahead of a major earthquake won't be possible until the entire network of sensors is finished.

"We have to just hope the thrust fault stays solid over the next few years," Moran said.

The B.C. Government has put $5 million towards the earthquake early warning system.

The next step is to determine how a warning can be distributed so people have time to take cover, said Moran.

The warning from the sensors will go to Emergency Management B.C, but it will be up to the government agency to figure out how it can get the message out, she said.

Moran said an app that delivers emergency information via people's phone could be the answer.

"We'd like to think that would be the direction to go in."