What happens if a tsunami hits B. C.?
But seismic experts say there’s still a lot to be learned about earthquake preparedness
Cities such as Vancouver, Seattle, and Portland would be spared the damage incurred in Japan from a massive 8.9-magnitude earthquake and tsunami because they are not located on the exposed outer coast.
“ The advantage we have is that our population centres tend to be on the inland waterways,” Michael Bostock, a professor of earthquake seismology at the University of B. C., said Friday.
“ The main concern is the smaller coastal communities that face outward into the Pacific Ocean — Port Alberni, Tofino, Ucluelet.
“ We know there is going to be another large, great earthquake sometime in the next few hundred years off our coast. That’s a basic certainty. And there’s a good chance there will be a large tsunami associated with that. Not 100 per cent, but very likely.”
Bostock added the region can learn valuable lessons in the coming weeks in terms of the effectiveness of monitoring and early-warning systems employed in Japan, an international leader in earthquake preparedness.
“ Japan is among the most technologically advanced and most earthquake-savvy societies on the planet. I would expect Japan has the best monitoring systems ... state of the art.”
Amy Wright, a seismic analyst with the Pacific Northwest Seismic Network at the University of Washington in Seattle, agreed: “ For scientific purposes, this earthquake in Japan is really helpful to us because it’s very similar to the type of earthquake we could have here.”
She added that while Seattle might be largely spared from a tsunami, “ Some of our coastal towns could be completely wiped out by waves of three metres high, but our coast is not as heavily occupied.”
Japan and B. C. are located on the so-called earthquake-prone Pacific Ring of Fire.
Japan lies on the cusp of the Pacific-Philippine-Eurasian triple plate junction, making for complex and unpredictable seismic activity.
B. C.’ s major threat of earthquakes and tsunamis come from the eastward-moving Juan de Fuca tectonic plate sliding beneath the westwardmoving North American plate at the Cascadia subduction zone.
A catastrophic mega-thrust quake of 9.0 is thought to occur about every 500 years locally, the last occurring in 1700.
John Cassidy, a federal seismologist at the Pacific Geoscience Centre in Sidney, said the Japanese have “ literally thousands of seismographs on the ground,” the information from which will prove invaluable to scientists.
“ There will be many things learned from the earthquake and tsunami ... to improve our situation here,” he said.
“ Were there any signals, warning signs, anything obvious to help us understand if we’re closer to a big earthquake or not?”
Japan recorded an earthquake of 7.2 at the same location on March 9.
Cassidy said the data will also provide “ a really accurate picture of how the ground shook,” which can be compared with damage patterns to buildings and infrastructure and later lead to improvements in building codes and preparedness for the next earthquake.
A massive 9.0 earthquake and tsunami off Sumatra, Indonesia, in 2004, followed by the 8.8 Chilean earthquake in 2010 failed to provide such detailed information, he said.
The Sumatra disaster did lead to increased funding for B. C. coastal communities for preparedness, including sirens and maps of evacuation routes.
“ Even in Japan, they’re much farther ahead, but are still in the testing stage,” Cassidy said. “ We are not nearly at their level. It’s really in its infancy here, but we’re starting down that path. We’re working on it, but we’re not nearly as far along as Japan....”
Cassidy said there are about 150 standard seismographs positioned across Canada to record small to moderate or distant earthquakes. Another 100 “ strong motion” instruments are deployed on the West Coast, mainly southwestern B. C., to monitor for major local quakes, he said.
The earlier scientists know about the magnitude and location of an earthquake, the sooner they can issue public warnings and give people time to seek higher ground to avoid a tsunami.
“ With automated systems, you can shut down nuclear power plants ... stop traffic from going into tunnels or onto bridges, open the doors at fire halls so the trucks can get out,” he added.
The University of Victoria’s Neptune Project, which employs fibre-optic cable on the ocean floor, can record tsunamis and earthquake shaking and is in the process of being integrated into the greater coastal seismic network to provide faster information.
“ That’s the plan in the very near future,” Cassidy said. “ In this day and age, people not only want information quickly, they expect it. That’s a challenge in seismology. It takes some time for the waves to travel, so the magnitude of an earthquake will change over time as we get better data.
“ It takes time to get a final answer.”
Federal researchers are also looking at better ways of quickly locating earthquakes and tracking them for P or S seismic waves; the former is associated with up and down motion less damaging to buildings, the latter typified by larger and slower shear waves that shake side to side and are highly destructive to structures.
And what if B. C. experienced a quake similar to Japan’s? “ You’d see a lot of damage in coastal communities, the strongest shaking and a devastating tsunami following,” Cassidy said. “ They’d take the brunt of it.”
But there would also be “ significant damage” through Vancouver Island and parts of the Lower Mainland and all along the coast from central Vancouver Island south to California. Shaking would be stronger in Victoria than Vancouver, he added.
Cassidy emphasized there is “ no clear evidence” to suggest that the Japanese quake could somehow trigger a major quake off the B. C. coast, although surface waves from large earthquakes “ can, in some cases,” trigger small earthquakes great distances away as the waves pass through a region.
The message to be taken from the Japanese quake and tsunami?
“ Be aware we live in an earthquake zone,” Cassidy said. “ These earthquakes are rare but they’ve happened before and will happen again. Knowing what to expect and having a plan when you feel shaking, that can make a big difference.”
For information on preparedness, visit: www. pep. bc. ca.