Haida Gwaii earthquake yields new data
Science team probes quake fault along B.C. archipelago
Curt Petrovich, CBC News
Posted: Nov 26, 2012 5:42 AM ET
Last Updated: Nov 26, 2012 10:55 PM ET
A team of federal government scientists that descended on Haida Gwaii following last month's 7.7 magnitude earthquake is getting new insights into the fault that caused it — and the fear it generated.
Seismologist Alison Bird is one of about a dozen experts from Natural Resources Canada who were dispatched to the archipelago when the shaking started.
"My heart was in my throat until I started reading the reports, and started realizing that everyone's fine," Bird said.
There were no physical injuries from the most severe Canadian quake in more than 60 years, and Bird says the worst building damage may have been a cracked foundation and a crumbled chimney.
After spending the better part of three weeks debriefing Haida elders, school children, teens and adults about the experience, Bird says most handled it well — but it's clear not everyone came through the event unscathed.
"It really depended on the person ... There were some people who were extremely rattled. It's almost like a post-traumatic stress they're going through," Bird said after touring the region.
"Some people had to take time off work. Some children had trouble and needed to be comforted at school, and thankfully it's the kind of community [where] that was at their fingertips."NRC seismologist Alison Bird documents how people felt the quake. (Curt Petrovich/CBC)
Weeks after the quake, Haida Nation Coun. Cindy Boyko is spooked by any creak or groan in her house in Skidegate.
She still has a bag packed by her door, and a truck in the driveway is loaded and ready to go.
"That night was terrifying," Boyko said. "It's the scariest thing I've ever been through in my life."
Boyko says she expected the shaking to stop after a second or two. When it didn't, she was paralyzed with panic.
"I knew I had to just move, so I did. I got up and made a run for the hallway, hanging on to the moving walls, walking on the moving floor. So I ended up in the doorway just hanging on, screaming for my husband. "
Boyko described the sound of the quake like a freight train coming from beneath her floor.
Bird is paying close attention to experiences like Boyko's.
She says they will help planners understand the psycho-social impact of natural disasters, and how they might play out in a more severe event in a more populated area.
But descriptions of how the quake felt are also giving scientists a clearer picture of the geological event itself.
"The information I'm getting from these people can actually be translated into intensity," Bird said.
"We've been doing intensity maps for decades, and what it does is it gives you an idea of the level of ground motion, or level of movement in those different communities. From that we can gain a lot of information about the characteristics of the earthquake."
She says the people of Haida Gwaii have become human sensors.
"We only have really a handful of seismometers around the Haida Gwaii region," Bird said. "But we've got 4,000 people so if they tell us how they experienced the earthquake, it's almost like they become another seismometer."
Thousands of quakes
Geophysicist Mike Schmidt was first on the ground after the initial quake.Geophysicist Mike Schmidt installs GPS receiver on Hot Springs Island. (Curt Petrovich/CBC)
"It's exciting and I think a lot of us are saying this is probably a once-in-a-lifetime sort of thing."
Schmidt oversaw the installation of seven new seismometers throughout the island chain, which relay data in real time to scientists in Ottawa and Sidney, B.C.
As well, six new highly precise global positioning receivers Schmidt's team placed will measure every heave and sigh of the earth's surface as small as a millimetre.
"I mean people are feeling it," Schmidt said of the continuing aftershocks.
"Every day I come into the restaurant in Queen Charlotte City and people say, 'Well did you feel it last night?'. And so there are still earthquakes out there, people are feeling them. If you take all of them, including the tiniest ones, we're into well over two or three thousand earthquakes right now."
It wasn't easy finding suitable sites for the new sensors on short notice — the equipment had to be mounted on bedrock, and Schmidt and his team had to use helicopters to hop islands.
Schmidt also had to make sure the Haida Council was comfortable with the placement of satellite dishes, solar panels and other gear in places like Gandll K'in Gwaayaay, or Hot Springs Island, a sacred site in Gwaii Haanas National Park Reserve that's also a carefully managed tourist attraction.
Hot Springs vanished
"Well it's funny," Schmidt said. "Right after the earthquake and laying out the preliminary plans, of course everybody was saying 'OK, let's go put one on Hot Springs Island.' Everybody was volunteering to go there."Carey Bergman of Parks Canada stands in a once overflowing hot spring, now dry. (Curt Petrovich/CBC)
But right after the quake, the bathing pools which are fed by 30 C water heated several kilometres under ground abruptly dried up. Now the basins collect only cold rain water.
Some people have now taken to referring to the retreat as Not-Springs Island, and everyone's asking Schmidt if their measurements will tell them if the hot water will return.
"We just don't know," Schmidt said.
"The plumbing changed when the earthquake happened. We do know that after other earthquakes, other hot springs in other parts of the world have gone dry and have come back. We just don' t know what's going to happen here."
Predicting the next quake
Schmidt must also disappoint anyone looking for a definitive answer about when the next major quake will rumble through the region.
He says the data they're collecting won't yield any clues, but will ultimately help people prepare for the next one.
"All this work we're doing is to try to get a sense of the type of earthquake [it was] ... what kind of shaking, how long the shaking will take, what kind of G-forces we're likely to experience," Schmidt said.
"All of that information is then taken and we give it to the engineers and that goes into the building codes. From that we just get a better infrastructure."
The data is also helping researchers get a picture of what happened.
A GPS receiver at Sandspit that was active during the quake recorded a shift of 20 centimetres.
But seismologist John Cassidy says closer to the epicentre along the Queen Charlotte fault, the Pacific tectonic plate may have moved as much as four metres in a rare and violent collision, rather than a routine slipping of the plates against each other.
"Our thought at this point is that this earth quake represented the Pacific plate being pushed beneath Haida Gwaii," Cassidy said.
It's a theory that could take specialists with Natural Resources Canada several months to verify as they pore over the data flowing from the newly installed sensors.
Boyko had hoped all the science being done on her doorstep would ultimately find a way to give her increased warning time.
"So we aren't sitting around all scared, just waiting for the next shake to happen ... so we can be prepared and get out of the way if we do have a tsunami," she said.
There's not much earthquake scientists can do to predict the next big one but Boyko is still glad to see them study the last one so closely.
"I think Hot Springs was a small price to pay for what we went through," she said.
"I think it was a wake-up call. I have to evaluate what's important to me, and not take it all for granted. I love Haida Gwaii. I want to protect her. But in the end it's my family that's important — my family and the people we live with."
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