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How can science help keep us safe?
A growing global population means that earthquakes have increasingly devastating consequences. In Canada, many of our major urban centres are vulnerable. Find out what some Canadian scientists are doing to help predict when and where earthquakes will happen.
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At 2:46 p.m. on March 11, 2011, Japan's northeast coast was shaken by a magnitude 9.0 earthquake, the largest ever recorded in the country's history. Twenty-six minutes later, towering tsunami waves rolled in. As of June 2011, more than 14,000 people are thought to have died, although the true tally may never be known.* The World Bank ranks it as the world's costliest natural disaster, with economic damage estimated at $235 billion.
The Indian Ocean tsunami, on the morning of December 26, 2004, was triggered by an even larger magnitude earthquake (9.2). It was much deadlier, claiming the lives of more than 250,000 people in 14 countries bordering the Indian Ocean. The economic cost of $14 billion, however, was far less than in Japan, “partly because of low property and land values in the affected areas,” according to The Economist.
These cases illustrate the reality of natural disasters in the 21st century, says Dr. John Clague, Canada Research Chair in Natural Hazards and Director of the Centre for Natural Hazards at Simon Fraser University. “In poor countries, deaths from natural disasters are increasing, while in wealthy countries, economic damage from natural disasters is increasing.”
The impact of earthquakes in Canada
Are earthquakes more frequent?
Given the litany of recent devastating earthquakes, it may seem that we're going through a time of increased seismic activity, but we're not.
In Canada, happily, there have been no major earthquakes to date that have led to large-scale property destruction and personal injury or death. Many of our major urban centres, however, are vulnerable to earthquakes to some degree.
The west coast is Canada's most seismically active area ' of the approximately 4000 earthquakes recorded annually in Canada, half occur in or offshore British Columbia. This puts Vancouver and Victoria at the top of the list of urban centres at risk. But Montréal, Ottawa, Toronto and Quebec are all at risk of an earthquake as well.
The Canadian Risk and Hazards Network has concluded that a significant earthquake is Canada's greatest potential natural disaster, seeing as much of our urban infrastructure predates the seismic-based building codes introduced in the 1970s. The magnitude 6.7 Northridge, California earthquake in 1994 illustrates the level of damage that could occur on Canada's West coast under similar circumstances. It left 60 people dead, 7000 injured, and more than 40,000 buildings damaged in Los Angeles and surrounding counties.
Engineering for earthquakes
Canada's seismic activity is monitored by Natural Resources Canada, which maintains a network of 160 seismographs that monitor earthquakes and measure ground movement in all parts of the country. This information feeds into the National Building Code of Canada, which serves as a model to help provincial and territorial authorities ensure that structures are engineered to the level of earthquake hazard for their locale.
Although it's not yet possible to predict exactly when and where an earthquake will occur, Canadian scientists are carrying out a range of geophysical studies, both on land and offshore, to develop reliable prediction methods.
Measuring tremors to forecast earthquakes
At Natural Resources Canada, one project with strong potential benefits uses global positioning satellite technology to measure clusters of miniscule tremors along faults that form where the Juan de Fuca tectonic plate is being forced under (or subducted beneath) the North American Plate. This is Canada's most earthquake-prone region, and great earthquakes of magnitude 9.0 or higher occur here on average every 500 to 600 years ' the last one being in 1700.
Earthquakes in southwestern British Columbia occur in three distinct source regions:
(1) Relatively close to the surface in the North American Plate (continental crust); (2) Deeper in the subducting Juan de Fuca Plate (oceanic crust); (3) Along the boundary between the North American Plate and the subducting Juan de Fuca Plate (locked zone).
Reproduced with the permission of Natural Resources Canada 2011, courtesy of the Atlas of Canada.
These clusters of miniscule tremors, known as “episodic tremor and slip” events, were first identified by seismologists at the Geological Survey of Canada in 2003. They occur like clockwork every 12 to 16 months and last for several weeks.
While more research is required to fully understand these events, seismologists are certain that they are a key to improving forecasts of when and where the next great earthquake will occur in the region. Other countries, such as Japan and Chile, with similar geological environments, are adapting this Canadian discovery to their own research.
"Science and engineering can help us to understand earthquakes and live more safely with them. But at the individual level, we have to know the basics of emergency preparedness, so if an earthquake strikes we will have a better chance of getting ourselves and our loved ones through it."
Dr. John Clague, Simon Fraser University
A watery ear on the Earth's pulse
Another project is taking advantage of NEPTUNE, one of Canada's most exciting big science projects. NEPTUNE has wired an 800-kilometre loop on the seafloor of the Juan de Fuca Plate and sprinkled it with instruments that allow scientists of all disciplines to conduct experiments via the Internet.
Pinpointing buildings at risk
The geology under any area determines the intensity of shaking during an earthquake. Researchers are working on maps that will pinpoint the seismic risk faced by particular buildings in major cities. Learn more.
Do you know what to do during an earthquake?
If an earthquake rattles your world, “Drop, cover and hold on” is your mantra. Drop to the ground, take cover under a sturdy piece of furniture, and hold on until the shaking stops. Learn more.
Using NEPTUNE, researchers at Natural Resources Canada have set up a deep-water seismograph network that records real-time seismic activity on the Juan de Fuca Plate. This data is fed into the land-based Canadian National Seismograph Network, which is used to determine the size and location of earthquakes as they happen.
Dr. Clague suggests there could be another interesting theoretical application. Should a big earthquake occur at the plate interface, it would be picked up by the NEPTUNE seismometers in real time and transmitted to shore stations, arriving as much as a minute before the earthquake hit Victoria or Vancouver.
Granted a minute is not much time, but Japan had that much advance warning from their monitoring systems at the start of the March 2011 earthquake. This gave them enough time to shut down their railways, preventing the possible derailment of high-speed trains due to the shaking and averting another level of human tragedy.
Earthquakes happen: be prepared
The Earth is in constant motion, full of tremors and twitches, as its plates push into and under each other. Dr. Clague points out that earthquakes, devastating as they can be, are just part of the natural order.
"Science and engineering can help us to understand earthquakes and live more safely with them,” he says. “But at the individual level, we have to know the basics of emergency preparedness, so if an earthquake strikes we will have a better chance of getting ourselves and our loved ones through it."
ISSN 1927-0275 = Dimensions (Ottawa. Online)