February 12, 2019 – Prof. John Clague, “Earthquakes and Tsunamis”

John Clague
Professor and Shrum Chair in Science
Simon Fraser University

John Clague is one of Canada’s leading authorities in Quaternary and environmental earth sciences; Professor and Shrum Chair in Science at Simon Fraser University; Emeritus Scientist, Geological Survey of Canada; Fellow of the Royal Society of Canada; Professional Geologist, Association of Professional Engineers and Geoscientists of the Province of British Columbia; 30 years experience in surficial/terrain mapping, Quaternary stratigraphic investigations, engineering and environmental interpretations of surficial geological information, and natural hazard studies; noted for local, national, and international research collaboration with other geologists, geographers, biologists, and physicists.

Dr. Clague has published 200 papers, reports, and monographs on a wide range of earth science topics of regional and national importance. He has prepared innovative geoscience products for educators and the public. He has had numerous television and radio interviews (CBC Newsworld, CBC Radio, CTV Television) and has been featured in newspaper and magazine articles (Vancouver Sun, Victoria Times-Colonist, Equinox, Beautiful B.C., Westside News, The Westerly News). Clague’s research was featured in a 1997 Discovery Channel documentary on earthquakes and tsunamis on the west coast of Canada. He has influenced Quaternary scientists in the United States and Europe and his research on earthquakes, landslides, and floods has greatly increased public and official awareness of these hazards.

Q&A

Q: What’s the likelihood of a very large rockslide, like the Hope Slide, occurring on the North Shore?

A: I would say that’s very low, only because we haven’t seen the geologic evidence of a big landslide like that since the end of the last glacial cycle. So, in 10,000 years, we haven’t seen a big landslide on the south plains of the North Shore mountains. Not to say that you wouldn’t get a lot of smaller events, but I don’t think that you’d get a catastrophic failure like the Hope Slide, even during an earthquake there. You’re more likely to cause these fairly small rockslides or rockfalls on steeper slopes. So, in an earthquake, the only place I would think would be an issue is if you happen to have a property below a very steep rock slope, I would say, near vertical, I’d worry a bit about that, but not that the whole mountain side is going to collapse.

Q: I know that from listening to the news, there was some correlation between fracking and earthquakes in Northern BC and I think places like Oklahoma, that never had had earthquakes.

A: Oklahoma is an interesting case because it’s in the middle of a continent, it’s never had earthquakes, and then they started this fracking or hydraulic fracturing, and they began to get earthquakes, some of them at the threshold of damage, up at around magnitude 5. And they had hired a seismologist, which I thought was a hoot, because you know, the Oklahoma state geologists are the seismologists, but definitely in some areas, Oklahoma, Northeastern BC, the foothills of Alberta, you can induce earthquakes by fracking. They are very shallow, they occur along existing faults, and they typically are small, I think we’ve had an event close to up to magnitude 5, so the threshold of damage. And the two causes, sort of generically of those earthquakes, one is that you’re injecting fluids under very high pressure to fracture these oil-bearing rocks, and that pressure apparently is enough to cause slippage along existing faults. In other areas, typically what they do, they bring the fluids that they use to frack up to the surface, and they recover them, and then they reinject them into the ground somewhere else. And they reinject them under pressure and that can cause earthquakes in some areas too.

Q: Thinking about the mine tailings disaster in Brazil, which was by all appearances almost spontaneous, and there are something in the hundreds there, and I know this isn’t here, but there it strikes me that if they had any kind of a shake, that this could precipitate a whole lot of other failures.

A: Yes, that’s a powder keg down there, because they’ve got hundreds of these tailings dams and they’re not well designed. That was a case of liquefaction, I don’t know if you’ve been online and actually there’s a 20-second YouTube video that shows the collapse of the dam. You can see the liquified zone at the base of that dam going out. It becomes suddenly very dark-coloured. Well that’s the water kind of liquifying the soil. They don’t get earthquakes in that area, so at least they don’t have to worry about that, but I would say that these are improperly engineered tailings dams, and there’s hundreds of them. So that’s kind of a powder keg for them. We have lots of tailings dams in BC. We had one failure, Mount Polley. We have higher standards and whenever you have a significant tailings dam, you have to design them to withstand the expected ground shaking in the area where they’re built.

Q: A bit of information for Probus members who may not be aware, but the city of Vancouver, about 30 years ago, installed three pumping stations to fire pressurized sea water into the West End area. I know where two of them are, and there’s a plaque on them to notify you, on West Cordova and I think Bute Street, I’m not quite sure. There’s another one as you’re travelling north on Cambie Street, on the south side of False Creek, you’ll see some pipes sticking up, that’s another station. The third one, I’m not sure exactly, but it may be in this area somewhere, Kitsilano. The city installed it, I think 30 years ago, to put out any fires. I don’t think that they’ve ever been tested. Out of interest, by the way, one of our Rotarians, Don Evans, I think who was in charge of the emergency earthquake committee of the time, I think he probably got that started.

A: Yeah that was a measure, and I remember that. Thank you for that information, I didn’t realize where they were located. What partly drove that was the loss of these vessels that could pump water onto the waterfront. There was a point when the federal government decommissioned, or we lost that capability, but we have it back now so, we have the capability of fighting fires on the industrial water front. And these might not be earthquake related, they could be due to any cause.


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