December 5, 2016 by Heather Kent
During the first half of this year, earthquakes claimed the number one spot as the costliest disaster type, wreaking over US$34 billion* in economic havoc, and placing seismic risk preparedness top of mind amidst the settling ashes of wildfire-dominated discourse.
This was largely thanks to two devastating earthquakes in Japan in April, but turning homewards, the recent discovery of a second active fault near Vancouver Island has prompted serious investigation into seismic risk preparedness in Canada.
Speaking at a panel presentation on preparing for seismic risk at this year’s National Insurance Conference of Canada (NICC) in Vancouver, Dr. Trevor Allen, earthquake hazards seismologist at the Geological Survey of Canada and a member of the National Building Code (NBC) of Canada’s Standing Committee on Earthquake Design, explained that Canada’s West Coast, with the Pacific and North American plate boundaries in close proximity, represents the region of greatest earthquake risk. However, the St. Lawrence River region of Montreal and Ottawa also contains potential risks, with Eastern Canada experiencing about 450 quakes per year.
Past major events include the magnitude 9.0 Cascadia earthquake in Oregon in 1700, and the 8.1 earthquake in Haida Gwaii in 1941, where a 7.8 earthquake was felt in 2012.
Seismologists have since warned of The Big One that will strike along the Cascadia subduction zone, which reaches as far as the north end of Northern Vancouver Island. However, new evidence suggests the presence of a potentially active fault just south of Vancouver Island, the Devil’s Mountain Fault zone. Because the shallow rift fault is close to downtown Victoria, an earthquake could result in devastating destruction, but scientists do not yet know the extent of the potential threat. “It is difficult to identify faults in the earth’s surface,” Allen said. The Devil’s Mountain Fault zone runs from Washington State to Victoria, and it’s possible that the Devil’s Mountain Fault and the Leech River Fault—which runs east to west across the southern tip of Vancouver Island, past Victoria—could connect beneath the ocean at some point.
The three types of earthquakes are: subduction, where plates become locked and build up stress to a rupturing point, in– slab earthquakes start from the deepest point and are usually limited to 7.0 magnitude; and shallow crust events, which occur at about 10 kilometres beneath the earth’s surface, Allen explained.
In-slab earthquakes present the largest threat to one to three storey buildings, causing high frequency ground shaking. Large, high–rise buildings are more susceptible to subduction earthquakes, which create longer periods of ground shaking. The NBC’s earthquake hazard maps were updated in 2015 to show the shaking level probability of quake scenarios in every region of the country. The mapping shows a 10 per cent chance of moderate damage in Victoria, and 4 per cent in Vancouver, within the next 50 years.
Researchers are using shake maps, considering random scenarios in order to form a picture of shaking distribution probabilities, and using ground motion models to estimate the likely amount of shaking at given distances from an earthquake’s epicentre. The risk of physical damage is highly sensitive to input ground conditions, Allen explained. Following the 1999 earthquake in Turkey, Allen developed 26 local scenarios, estimating fatalities ranging from 200 to 200,000, representing two orders of magnitude difference. This shows the very large scope of inherent uncertainty, he said.
Although Canada’s major earthquake potential hazard zone is in south–western British Columbia, south-eastern Ontario and Quebec are also at risk, although they are nowhere near plate boundaries, said Dr. Tuna Onur, seismic risk consultant and a member of the NBC’s Standing Committee on Earthquake Design.
The probability of ground shaking structurally damaging older buildings in Vancouver within the next 50 years is 15% in older buildings, Onur said. However, what is underneath each building also matters during a quake. Differences in geology can increase the duration and amount of ground shaking, as waves can become trapped. And, because of changes in building codes in recent years, buildings will behave very differently, depending upon their age, during an earthquake, Onur said. The greatest amount of damage occurs in buildings with a “soft storey” ground floor, which is more open and less stiff than the storeys above it. Damage is caused when increased loading results in a deformation yield; when the loading passes the “ultimate” point, the building will collapse, Onur explained.
Beyond property risk, insurers also need to consider associated earthquake damage caused by casualties, liquefaction, landslides, fire, tsunamis, business interruption, non–structural elements and contents. For instance, damaged equipment in hospitals would probably be worth far more than the buildings, Onur said.
Onur pointed out that the NBC’s codes only become law when individual provinces adopt them, and enforcement only occurs at the municipal level. B.C. took two years to adopt the 2012 building code. Meanwhile, the latest NBC code was launched in 2015, and discussions are underway regarding the 2020 code. The only goal of the NBC is to minimize loss of life by preventing building collapse, Onur emphasized.
Until the adoption of the 2012 code, many wood-frame houses in B.C. were not anchored to their foundations, creating soft storeys on the ground floors. Now builders have to place boards diagonally, rather than horizontally, on ground floors to reduce ground shaking risk. Apartment buildings with “tuck under” open parking areas offer very little seismic resistance as they are too open, and unreinforced masonry construction in heritage buildings carries the highest risk in major cities in both Western and Eastern Canada, Onur said.
The City of Vancouver is looking at its built environment and how to mitigate potential earthquake damage to its people and economy, explained Daniel Stevens, director of emergency management.
Where do people go after an earthquake and how do you get people back? What are the long-term impacts? “The ultimate purpose of emergency management is to save lives, preserve the environment and protect property and the economy,” Stevens said. This is a collective community effort, he added.
Vancouver has its own building code and wants to adopt the 2015 NBC quickly, Stevens said. The City is currently focusing on earthquake mitigation in municipal properties. For example: it is demolishing the east wing of City Hall this fall and planning to use resilient water pipes from Japan in high-risk areas. A dedicated fire protection system, which can use salt water, will be constructed.
Private sector ownership of the most critical infrastructure, such as pipelines, is one of the main challenges in earthquake preparedness efforts, Stevens said. Another is conflicting priorities between affordability and seismic resilience for expensive upgrades. Many buildings do not, therefore, undergo retrofitting.
The City’s ongoing community engagement efforts include the annual ShakeOut B.C. earthquake simulation event and running 25 Disaster Support Hubs throughout the municipality. The goal is to progress beyond awareness to taking action on earthquake risks, Stevens said. Similarly, in October, Quebecers were invited for the first time to experience an 8.0 magnitude quake through the Insurance Bureau of Canada’s Quake Cottage, a mobile earthquake simulator, as part of its earthquake preparedness campaign.
At the end of the day, as panel moderator Maiclaire Bolton, senior product manager, Global Earthquake Products, CoreLogic, aptly concluded: “The earthquake is inevitable, but the disaster isn’t.”
* According to Aon Benfield’s First Half of 2016 Global Catastrophe Report.
Copyright © 2016 Transcontinental Media G.P. This article first appeared in the November 2016 edition of Canadian Insurance Top Broker magazine
This story was originally published by Canadian Insurance Top Broker.