Is Vancouver Ready for the Big One?
Canada's earthquake expert, seismologist John Cassidy, tells us what to expect when the Big One hits.
January 17, 2017
Be thankful for the little earthquakes that shake us—they serve as much-needed reminders that a 7- to 9-magnitude event looms. The treacherous Juan de Fuca plate will eventually buck up and the ground will move, a lot more destructively than the 4.7-magnitude quake felt across Vancouver and Vancouver Island in December 2015.
There are reasons to be nervous. Especially when earthquakes still scare one of the country’s foremost experts, John Cassidy, a seismologist with Natural Resources Canada. It’s Cassidy’s job to better understand earthquake hazards through research, including looking for hidden faults and mapping the forces that cause earthquakes. His realization after 30 years of doing this: there’s no way to predict when the Big One will hit.
Q: What is the reaction you get when people meet you for the first time and find out you’re an earthquake expert?
A: Everyone I meet is really appreciative of the work—because it does protect people’s lives and structures and ultimately our economy—and they’re really interested in what kinds of earthquakes we’ve had in the past. Most don’t know there was a 7.3 earthquake in 1946 and a magnitude-9 back in 1700, and we know energy is being stored for another big earthquake to occur here.
Q: What has been the greatest advancement of tools or techniques in understanding earthquakes in your lifetime?
A: Very precise GPS that can track tiny movements of the earth’s surface. That just started 20 to 25 years ago, with instruments deployed where you can start tracking the movement of how the surface of the earth is being formed. That’s part of how we discovered the Cascadia subduction zone where these magnitude-9 earthquakes occur. We didn’t know they occurred off our coast.
Q: What’s better to have: instruments or tools that can predict earthquakes, or an informed public who knows what to do when an earthquake hits?
A: At this point in time we can’t predict earthquakes. We can assess where earthquakes can occur; we can model and say this is the level of shaking we can expect. That’s the information we can use in building codes. It may be that we can never predict earthquakes. So I believe the most important thing is having an informed public and having well-designed building codes that incorporate the latest earthquake science.
Q: Why can’t we predict earthquakes?
A: We’ve heard of animals in China that may exhibit strange behaviour before an earthquake, but that doesn’t happen before every earthquake and not in every area. There have been some interesting observations at different times. The real challenge is finding something that is consistent and works all the time.
Q: Do you know right away, “I am in an earthquake,” or do you wonder, “What just happened?”
A: With small earthquakes, it can be hard to tell. It can feel like a gust of wind or a big truck. With bigger earthquakes there’s no doubt and it’s very frightening because earthquakes occur without warning. The first shaking we feel is the P-wave, a sound wave that travels, and that’s not the strongest shaking, it’s the up-and-down shaking. The shaking that causes damage are S-waves—that’s the side-to-side shaking—and they travel slower than P-waves.
Q: What’s the future of seismic preparedness and what does that look like for Vancouver?
A: I think back to when I was growing up in Victoria and there were no earthquake drills in school, there was no talk about seismic upgrades. Now we see bridges being retrofitted and, in Victoria, the old buildings being retrofitted. Before, we only had fire drills, and now we’re regularly doing things like ShakeOut. It’s all good progress. It’s important for individuals to have earthquake kits and to know what to expect; that’s at the personal level of preparedness. As a scientist, the work we’re doing in earthquake research and working with engineers to design buildings and bridges and infrastructure that prevents shaking is working. As federal government scientists, our research feeds into national codes and standards used every day by engineers and regulators and decision makers.
Q: What is something people don’t know about earthquakes?
A: Knowing what to expect is the best thing you can do. Large earthquakes are followed by smaller shocks. I was in Chile and for days, even weeks, you feel non-stop aftershocks, and up in Haida Gwaii in 2012, there were hundreds and hundreds of aftershocks. It’s always frightening. You feel the ground shake every hour, every half an hour. In Chile, I was in a store and a can fell off the shelf and I just about jumped. You’re on edge and you experience this feeling of being very frightened.
Q: Hearing that you’re afraid of earthquakes makes me even more nervous.
A: The key message is that we can protect ourselves from earthquakes. You asked how people react when they meet earthquake scientists, and one of the things that comes through is that people are really happy to hear earthquake scientists live in earthquake zones and we’re not in Saskatchewan, where earthquakes don’t happen. We live here, where earthquakes have occurred and will occur.
Q: What is the future for us here in Vancouver, and in B.C., if we can’t predict earthquakes? Do we just live with uncertainty until the Big One?
A: What is known is that there has been a great deal of data that has been supplied and used. Engineers have used that information; there have been upgrades made to infrastructure, building codes. We are much better off now than we were even 20 years ago because we have that much more research—even something like more detailed maps that allow us to see through vegetation and trees. We have new tools that allow us to get very detailed images of the sea floor to identify active faults. Every day we know more, and when people are prepared, we can now know what to expect. If people know what to expect, and they’re prepared and they know what to do after the earthquake occurs, that will minimize the impact of future earthquakes. And there will be future earthquakes.