B.C. early warning system in spotlight on anniversary of megathrust earthquake

B.C.'s earthquake early warning (EEW) system is in the spotlight once again as the anniversary of a massive 9.0-magnitude megathrust earthquake arrives.

On Jan. 26, 1700, one of the largest earthquakes to ever occur in the world rumbled off the west coast of North America.

The earthquake spanned from the northern tip of Vancouver Island down to northern California, wiping out homes, causing floods and knocking people off their feet.

Local Indigenous communities handed down stories of the incredible earthquake, tsunami, and aftershocks that occurred due to the Cascadia Subduction Zone rupturing, with the dates corroborated by scientists in Japan, who had written records of a tsunami reaching their shores from an earthquake originating from elsewhere in the world.

"[The earthquake] is very well documented in the oral traditions of First Nations groups from Vancouver Island down to California," said earthquake seismologist John Cassidy on Victoria radio station CFAX 1070.

"All of these Indigenous oral traditions describe exactly what we expect from one of these subduction earthquakes," he said.

Vancouver Island sits on the Cascadia Subduction Zone, and Cassidy says recent research into seismology has shown that 19 similar massive earthquakes related to the movement of the subduction zone have occurred over the past 10,000 years.

Each of the earthquakes occurs in a range of about 200 to 850 years, and Canada is looking at ways to prepare for future earthquakes.

323 years ago tonight (9 p.m. Jan. 26, 1700) a M~9 #Cascadia subduction earthquake rocked the west coast from #VancouverIsland to northern #California.
The Juan de Fuca Plate slipped as much as 20 m, causing a large tsunami, strong shaking and landslideshttps://t.co/l7nbpB7Q0G pic.twitter.com/4FJUeyFhzo

— John Cassidy (@earthquakeguy) January 26, 2023

NATIONAL EARTHQUAKE WARNING SYSTEM

Canada is building about 400 EEW sensor stations across the country, including more than 100 planned for British Columbia.

The early earthquake warning sensors are designed to pick up on seismic waves that occur right after an earthquake is triggered.

The sensors will give residents precious moments before the rumbling of an earthquake reaches them.

"So there is an opportunity for warning time depending on how far away the earthquake is," said Cassidy, noting that a massive subduction zone earthquake in B.C. would occur offshore.

"If you're very close you may only have five seconds or 10 seconds, but if the earthquake starts further away, say off of Oregon or off California, it could be four minutes to five minutes of warning," he said.

"It's not a lot, but it's certainly enough to get under desks or get under tables – time to get away from cabinets that may fall over, time for surgeons to put down scalpels, time to open garage doors at fire halls, stop elevators so people can get out," he said.

"So a lot of things can be done automatically with a very short amount of warning time."

Canada's national EEW network is scheduled to complete in 2024. The EEW stations are centred around regions where there is a threat of a significant earthquake, particularly around areas with high populations or that contain critical infrastructure, like power stations or rail lines.

Cassidy says the earthquake early warning system is an "important tool in our tool belt" to protect against earthquakes.

Other important tools include modern building codes and preparedness from residents.