On shaky ground

We can’t stop earthquakes from happening, but good engineering can help mitigate the risk they pose to billions of lives every day.

by Sean Rushton

The recent disasters in Haiti, Chile and China have brought new attention to the devastation that can be wrought in the world’s subduction zones, areas where the Earth’s tectonic plates grind against one another and are prone to sudden shift s that cause significant seismic events, or “megaquakes.”

Just such an area exists only slightly west of Vancouver Island, where an undersea fault called the Cascadia could potentially bring the bustling city of Vancouver — and possibly Portland and Seattle — to their knees. 

“This fault has the same characteristics as the fault that ruptured in Southeast Asia in 2004, causing major tsunami and earthquake damage,” says Murat Saatcioglu, a civil engineering professor at the University of Ottawa and one of the world’s leading edge earthquake scientists. “It’s also very similar to the fault mechanism we just saw in Chile, so the type of ground shaking we would see in Vancouver would likely be almost identical.” 

Indeed, the Canadian Risk and Hazards Network asserts that a significant earthquake is probably Canada’s greatest potential natural disaster. The question begs to be asked then: What can we do to prepare ourselves to help reduce loss of life and property in the face of such an eventuality? 

Over the centuries, many efforts have been made to predict earthquakes. Yet the truth of the matter is that earthquakes are going to happen whether they are successfully predicted or not. Therefore, one rational step in mitigating seismic risk is to strengthen and retrofit seismically deficient structures. These structures were oft en designed and built prior to the enactment of modern seismic codes and are, therefore, vulnerable to earthquakes. 

However, the inventory of seismically deficient buildings and bridges worldwide is very large, and it is not economically feasible to retrofit each and every one of them. Therefore, the assessment of seismic risk is an important first step in order to establish priorities before engaging in costly retrofit projects. The recognition of this important step has motivated Saatcioglu to spend a lot of his career travelling to earthquake-stricken regions. 

“I am oft en involved in earthquake reconnaissance visits after major quakes,” he explains. “People in disaster areas are desperate for advice, and as we walk around damaged areas, they often circle us and start asking questions in order to salvage what is left of their buildings.” 

“The psychology of people in disaster areas is one of hopelessness and desperation. They want to do something about their buildings after the fact, when it is oft en too late. Therefore, it is important to develop public outreach programs and sensitize people about the need to reinforce their buildings so they are more earthquake resilient.” 

Saatcioglu recently returned from Chile where he led a team of 10 scientists examining why some buildings remained standing while others fell down, and to try and determine if similar structures in Canada would react the same way. 

The Chilean disaster represented a unique opportunity for Saatcioglu and his team to study the various factors that could determine the outcome of such an earthquake on Canada’s West Coast, not only because similar tectonic forces are at play but also because Canada and Chile share similar buildings codes and seismic risk mitigation practices. 

One of the reasons the damage in the recent Chilean earthquake was not as extensive as the damage seen in Haiti — even though the earthquake in Chile was significantly stronger—is that Chile, unlike Haiti, uses modern building design practices to design earthquake resistant buildings. 

“Making structures behave in an earthquake-adaptable manner is full of challenges, but necessary for seismic risk mitigation,” states Saatcioglu. 

“Unless we research and develop seismic risk mitigation techniques, in terms of developing cost-effective and sound retrofit strategies, and improve the strength of our cities, we are prone to seismic risk and potentially devastating catastrophes.” 

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