When the earthquake hits, here’s the real worry (according to one UBC prof)
Key takeaway: the buildings most at risk aren't always the ones you'd assume
February 4, 2016
When a 4.3 magnitude earthquake struck northeast of Victoria on December 28, the rumble was felt clearly throughout Vancouver. It was enough to get everyone talking, but also, mercifully, not enough to do any real damage. The next one, or the next-next one, may not be as forgiving. Perry Adebar, the head of civil engineering at UBC, says a significant earthquake is far likelier than an apocalyptic one, and the threat therefore isn’t so much that thousands will die but rather that thousands will end up homeless as buildings are damaged and deemed unsafe. Which buildings are most at risk? We spoke with Adebar to find out.
You’re currently researching the seismic risk of various buildings throughout Vancouver. How are you going about that?
We’re in the middle of looking at this very carefully. I have a PhD student looking at exactly this question. We’ve actually managed to get a hold of the drawings of about 350 buildings in Vancouver, so we have a pretty good idea of what the building stock looks like. Now we’re trying to apply scientific methods to try to come up with really reliable estimates of what the damage might look like.
How do you determine which buildings are most at risk?
The general feeling is the older the building, the less it’s been designed for seismic resistance, and that’s true to some extent. We didn’t know what was needed back in the ’70s. There are older buildings that will do wonderfully and new buildings that won’t do well, so it’s a bit more complicated than old/bad, new/good.
Can you expand on that?
The biggest issue, and people don’t realize this, is the architecture. The more complex the architecture, the more likely it is to get damaged. A simple building—nice, uniform, boring-looking architecture—is probably not going to get too damaged. [But] you get something with fancy characteristics in it and you increase the probability enormously. Add soft soil conditions, and in the West End there are pockets where it is softer. You put a building with bad architecture—from the point of view of a structural engineer—on a site with a little bit of soft soil, and you have a building that’s going to be damaged. The same thing goes for the brand new buildings. Some of the older buildings that were simple and nice, and the engineers put in lots of walls and lots of structure, the building’s going to be totally fine. But we see brand new buildings going up with crazy architecture, where they’re not going to be habitable after the earthquake.
Speaking of the West End, most of the buildings your research looks at are in that neighbourhood. Obviously there are a lot of towers that were built in the ’60s and ’70s in the West End. What’s likely to happen there in the event of an earthquake?
A lot of people focus on getting hurt and dying, but the reality is the big worry for Vancouver’s West End is not that. It’s more a sizeable earthquake coming along and a lot of the buildings being damaged enough that people aren’t going to be able to live in their homes. To me that’s the real issue we need to be focused on: a big enough earthquake that in a large percentage of those buildings people are going to say, ‘look, this is too damaged, we don’t want you to live in there.’
People err on the side of safety, and they vacate buildings that perhaps don’t need to be, but that’s just to be safe. So it doesn’t take a lot of damage before people say you can’t live here. Then what happens? Then we have all these empty buildings in the West End. It’s very high density. To me, that’s the big issue: not so much people dying and buildings collapsing. It’s more about buildings being badly enough damaged that people won’t be able to live in them. The chance of an earthquake of that size is much higher, and that consequence is quite severe.
What can be done?
I went down to Chile in 2010 when it was a very severe earthquake. People said don’t go down there, there’s devastation. You go down to the areas that are hardest hit and look around, and it’s one building in 10 or 20 that’s badly damaged. It’s not like all the buildings collapsed. So even in a really bad earthquake, the issue is not so much people dying, it’s people losing their homes. Some of those buildings in the West End, a small repair now could make them usable after a sizeable earthquake. Some of them maybe should be torn down, but most just need repairs.