The big one is coming: the B.C. megaquake. Researchers with the non-profit Ocean Networks Canada broke ground June 15 on a network of three sensors installed on the sea floor close to the Cascadia subduction zone just off British Columbia’s coast, which ought to be the beginning of an early warning system in case “the Big One” decides to strike.
Forecasters predict that the region, which sits where the Juan de Fuca tectonic plate slips eastward underneath the North American plate, is due for a magnitude 9 earthquake, which could strike any time between now and the next several hundred years.
Up and running as of the end of June, ONC’s sensor network is unique from similar systems in the United States, adding a crucial extra few seconds warning in the event of a major quake.
The last great B.C. megaquake was in 1700
The last great quake to affect the region around British Columbia’s southwest coast happened in 1700, a subduction quake that sent a tsunami towards modern-day Washington state’s coastline.
A subduction quake in Alaska devastated Anchorage in 1964.
The Ocean Networks array of sensors, funded with a $5 million grant by the B.C. government in February, may give a crucial few extra seconds edge warning residents that the Big One is on its way.
The sensor network is part of ONC’s NEPTUNE sea-floor observatory, which consists of approximately 840 kilometres of ocean-bottom cable looping beyond the Cascadia fault.
Signals are transmitted from the continental shelf to a shore station at Port Alberni, and then on to Victoria via fiber optic cable, and then further inland to Saskatchewan, in the event that the Victoria research station become incapacitated.
NEPTUNE director Kate Moran hopes to grow the network to 40 sensors during the next five years, and also to install a tiltmeter down a 300-metre borehole in the area, which would detect the nearly imperceptible, slower shifting of tectonic plates at the Cascadia fault.
The Japanese are still world leaders in earthquake detection, with a system in place since the 1960s for stopping bullet trains during quakes, and a public warning system since 2007.
Many clusters of slow-building subduction events were recorded in the lead-up to the March 2011 magnitude-9 Tohoku earthquake, which gave residents of nearby Sendai a 15-second warning and Tokyo residents a little over a minute.
Japan unveiled phase two of its undersea seismometer network in March, doubling the number of its detectors to 50, and has begun work on a 150-station network called S-net, with 5,700 kilometres of cable promising to provide up to 30 extra seconds warning during a large offshore quake.
A spate of magnitude 8 or larger subduction-zone earthquakes along North and South America’s west coast has been happening since 2004, generating more than twice the average events recorded in the previous century at 1.8 quakes per year, beginning in Sumatra and followed up by a tsunami-generating quake near Peru in 2007, and a smaller event in northern Chile in 2014.
The worst-case scenario for a B.C megaquake would involve a 1,000 kilometre rupture all the way down the west coast from B.C. to South America.
Ocean Networks Canada, affiliated with the University of Victoria, is one of Canada’s four major scientific initiatives, and has attracted over $230 million of federal funding to date.
ONC has been running its network of undersea cables and sensors off the B.C. coast for the past 10 years, reporting on a variety of ocean conditions, including temperature, salinity, and sediment content, data which is used by scientists, companies and the Canadian military, among others.
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