Its been 75 years since Canada's largest onshore earthquake occurred on the Island. We look back at that day and learn about how it happened. We also speak with a seismologist about the earthquake hazards on the Island today and into the future.
Its been 75 years since Canada's largest onshore earthquake occurred on the Island. We look back at that day and learn about how it happened. We also speak with a seismologist about the earthquake hazards on the Island today and into the future.
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Disclaimer: These interviews have been edited for clarity and length.
Jackie: Hi, my name is Jackie Lamport. Today is Wednesday July 7th. Welcome to the Capital Daily Podcast. Today on the show, 75 years ago, Canada experienced the largest on-shore earthquake in the country’s history. That happened right here on Vancouver Island. Today we look back on the event, how it unfolded, and how it impacted Islanders. At 10:13am on June 23rd 1946, Vancouver Island experienced the largest on-shore earthquake in Canadian history. The quake was a magnitude 7.3, and its epicentre was in the centre of the Island, the closest communities being Courtenay and Campbell River. Given the much lower population and lack of development on the island compared to today, the damage was not nearly as severe as it would be now, but it still shocked the entire island, and was even felt as far out as Portland, Oregon. Today we take you back to that day in 1946 to tell the story of what happened, the damage it caused, and the impact it left on the people at the time. We’ll also speak to a seismologist to learn more about if we’re set to see another quake just like this one in our future. First we welcome back to the show historian Kathryn McAllister. Kathryn, welcome back.
Kathryn: Thanks for having me back.
Jackie: Okay, so what happened on that day in 1946?
Kathryn: Yeah, so that was 75 years ago; we had the biggest earthquake, then definitely in living memory. On Sunday, June 23, 1946, at 10:13 am, there was a magnitude 7.3 earthquake on Vancouver Island, and it was Canada's largest historic onshore earthquake. A lot of them happened in the ocean.
Jackie: Can you tell me a bit about what areas were impacted and what happened?
Kathryn: Yeah, so the epicentre, the main point of the earthquake was in the forbidden plateau area, so central Vancouver Island. It wasn't populated, really, at that time, which was great because it meant that damage could have been a lot worse. So think west of Courtenay and Campbell River, Union Bay, Port Alberni; it actually reached as far as Powell River in terms of damage.
Jackie: What was the damage like?
Kathryn: Well, in some ways, it's not nearly as bad as it could have been. And then, in some ways, it was really significant. There were only two deaths, which is great. One person unfortunately drowned when a boat capsized because when you get an earthquake, it's not just the earth that is quaking; you also get tsunamis from changes in the ocean floor. So there was a boat that capsized due to a wave generated from the earthquake. And then another person had a heart attack in Seattle. The real casualties were chimneys. Apparently, about 75% of chimneys in the community surrounding the quake epicentre were just gone. Crockery was also a huge casualty; people had to buy a lot of new plates and glasses and that kind of thing.
Jackie: I understand that one of the deaths was actually in Seattle.
Kathryn: Yes. When an earthquake happens, we think of them as relatively localized events. But because of the geology of our surrounding area, earthquakes here can reach quite far, and it did. Someone had a heart attack in Seattle from feeling the quake's effects, and that's considered to be the other fatality other than the person who drowned.
Jackie: And some undersea power lines were destroyed, right?
Kathryn: Yeah, in the Alberni Inlet near Powell River. There's also a bunch of landslides on Vancouver Island. I think it was a beach in Campbell River that just turned into a cliff. So some significant things happened, but it was pretty good, all things considered. That's because Vancouver Island was not nearly as populated as today. There were 190,000 people there. Now it's four times that much on the island.
Jackie: You also sent a scenario modelled by the Emergency Management BC that helped us put that into context in today's population. What can you tell me about that?
Kathryn: There were two fatalities and a lot of crockery damage in 1946 because there weren't that many people here. But within that 7.3 magnitude earthquake. Now, that scenario suggests that there could be a death ball total of 10,000 people, more than 100,000 people injured, that these are always kind of rough estimates based on what we think could happen. We don't always know exactly. But there could be a bigger quake coming. And the results of that could be even more significant, not only for people's deaths but also for infrastructure. So when this happened, it was 1946. It was after the Second World War. Vancouver Island wasn't that populated; people still didn't fully understand plate tectonics. There was an idea of continental drift that had been sort of building in the scientific community. But it wasn't something that everyone understood. So even just the way that we understand earthquakes today is not necessarily the exact same as it was back then.
Jackie: So it would have been a lot more of a shock back then. Well, I mean, a lot of people were still asleep because it was a Sunday morning, so not exactly. Well, can you tell me a little bit about the reason the earthquake happened?
Kathryn: We live on what's called the Cascadia subduction zone. And it's, it's huge because we have the Continental plates that cover the molten core of the Earth and all the different layers. I'm not a geologist, but you have these plates that float on the surface of the world. And then we're right on top of that, and where the plates meet, you get kind of interesting results. We have the subduction zone, which is overlapping plates running from Northern Vancouver Island all the way to Northern California. It's something like 1000 kilometres long, between different plates overlapping, sliding below the very much larger continental North American plate, and then they're kind of stuck. So usually, they can slide back and forth, and you'll have little quakes, and it kind of builds off the pressure; right now, the fault is locked. So stress is building up and then every so often, in this case, 1946 there was some rupturing of the fault line, and you get an earthquake. And then how big it ends up being proportional to the length of the rupture along the fault line. You also get volcanic activity. A lot of people remember when Mount St. Helens erupted in 1980. That's an example of the effects of the Cascadia subduction zone.
Jackie: Has something like this happened before?
Kathryn: Yes, it's happened before throughout our history. The one that we can sort of pinpoint a lot more clearly is the 1700 Cascadia earthquake. This was January 26, and then 1in 700, it was a megathrust earthquake, so 8.7 to 9.2 on the Richter Scale, which is a lot more significant than the one in 1946.
Jackie: How do we know that that one took place? Because we know we didn't have the newspapers reporting on it.
Kathryn: There weren't newspapers back then. But what we do have is what we have science, and then we have oral histories, which in so many cases, the First Nations already knew about this. And then science is catching up with us. Along the coast, there are oral histories and a number of different First Nations communities telling of an earthquake and flood consistent with a tsunami that happened in 1700. It generally gets explained as a battle between a Thunderbird and a whale. So I guess the whale is the tectonic plate in the ocean, and then the Thunderbird is the land. So you have the Makah, the Kwakwaka'wakw, and a whole bunch of different groups all have these stories, going back generations about an earthquake and flood that was worse than any other.
Jackie: How has science caught up to that?
Kathryn: Yeah, so I think it's paleo geological evidence. Again, I'm a historian, not a scientist. There was saltwater that swept in abruptly and killed vegetation along the shore in certain areas. And it happens so fast that plants are preserved in a layer that you can dig down to and see. There are also ghost forests, which are these gray stumps, showing where the ground just dropped below sea level during this earthquake and allowed the water to flood in and kill forests. This is shown to be different from just a gradual rise in sea level killing them. Because if you look at their red cedar growth rings, the last year of growth is 1699. So that pinpoints it right at the same time.
Jackie: And is this still observable?
Kathryn: Oh, yeah, there's the ghost forest. There are various scientists doing research to take a look at when this happened. There are also records in Japan that there was an orphan tsunami that just came in really unexpectedly 16-feet high, right at the time that we know the earthquake happened here. So there's all these sources, oral histories, written records in Japan, and then also science confirming what people have already known.
Jackie: But going back to this 1946 event, that was thankfully just a little bit smaller. What was the coverage on that?
Kathryn: One of the great things about having the internet now is that you can go back and without leaving your home COVID or otherwise, you can find out a whole lot of information, which I took a look at under the Daily Colonist's archive online. So the Times Colonist, if you go to their site, you can find the British Colonist Newspaper going back to 1858, so I was able to take a look at some of the reporting for that.
Jackie: What did some of it say?
Kathryn: Well, apparently, in Port Alberni, one in every three chimneys was shaken down.
Jackie: You said it was the earthquake of chimney casualties.
Kathryn: They had a hard time. But it does also point out things like a girl was treated for leg wounds because there was glass flying off of a broken window. The post office was not doing well, the power plant. There were also some picnickers on a ship near going to Bamfield, and then they noticed that there was rumbling, and they had to stop the engines and try and figure out what was going on. With this kind of documents, you get something a little more interesting than just looking at an encyclopedia about it because you have a report of this minister on his way to the Alberni United Church, and he feels the quake. He thinks it's just his car dying. And so he goes, "Okay, I'm going to leave my car, get out." And by this point, the earthquake is over, so he walks to the church, he sees another motorist who also thinks the car's broken down, and then they get there. And this lady is like, "No, that was an earthquake, your car's fine."
Jackie: So it wasn't felt to the same extent across the island then, obviously, because some people thought that it's just their car broken down. What was it like in Victoria?
Kathryn: In Victoria, there's also a funny little clip from that. Apparently, their damage was fairly late, all things considered, but a local man was informed at the event by a friend shortly afternoon; he was more incredulous than angry. "Why didn't somebody wake me up?" He cried. "Don't people know that I can't sleep during an earthquake?"
Jackie: The things that get preserved.
Kathryn: And we don't know who that was. But I bet someone showed him that he was in the paper. I wonder how you felt about that.
Jackie: When looking back at the newspapers, I know it's also quite easy to get lost in what life was like back then. Can you tell me some of the interesting things that you saw from that time?
Kathryn: You just get so many different things that you weren't necessarily expecting in a newspaper. I mean, there'll be this person who came to visit and is staying in a hotel; you don't get that anymore. But then you also get serious things like a letter to the editor about the experiments, atomic testing happening and pointing out that the ethical viewpoint that deliberately planned suffering is wrong and the torture of animals deliberately undertaken is on quite a different footing to the destruction of beasts of prey or noxious creatures, which the phrasing gets me all the time. It's an article saying that the atomic bombing of animals is ethically offensive to many people. And we have to think about that when we're talking about atomic testing, which we don't always assume back in the day that people were aware of that kind of impact. And it's always interesting to see.
Jackie: Yeah, I think it's, we often forget, because the overall narrative of a time is what takes precedent in our heads. But there are the people who push forward. And that's the reason that we keep moving. So clearly, some people were ahead of the times, and that's how we get to the present day. The idea of being atomic bombing, being unethical toward animals, but that doesn't feel radical anymore.
Kathryn: It's nice to remind ourselves that attitudes don't always change that much. But at the same time, then you get a Colgate tooth powder ad that's just weirdly sexist, reminding people to brush their teeth before every date.
Jackie: You also pointed out in your notes to me a Safeway ad.
Kathryn: When you're looking through the old newspapers, you get to see a whole lot of details. You can see, there's a mention that there was a pharmacy that had $500 of damage. Well, what does that mean? If you get to see the Safeway, you can see that brisket was 14 cents a pound, ground beef was 23 cents a pound, cantaloupe, two pounds for 23 cents. The subscription to the newspaper for the year was $12. So you can see what people ate, how they lived, and then also how much money was worth back then.
Jackie: Your notes also mentioned an interesting bit from an article about the earthquake.
Kathryn: One of the people they interviewed was a couple of Chinese cooks at the Comox Logging Company, and they talked about their experiences. One of the friends comments that his washing machine was lost during the flood because it sailed off the porch of the camp and landed far off into the woods. The article will comment that the washing machine was a casualty. But then it also says things like there are 30-foot high waves followed by several others as high on the lake at Comox. And then you kind of see that there's some funny stuff going on. But you also see the amount of damage that could happen. These are huge waves. I can't even imagine that.
Jackie: Yeah, thinking of Comox today, 30-foot waves that would be devastating.
Kathryn: And they kept coming for some time. The waves happen for longer than the actual earthquake does.
Jackie: Kathryn, thank you so much again for joining us.
Kathryn: Thank you for having me.
Jackie: Now, we'll speak to Ed Nisson, a University of Victoria associate professor and Canada Research Chair in Geophysics. Ed, thank you so much for joining us today.
Ed: Yeah, thank you for having me.
Jackie: I want to first start off by learning what's unique about the position of Vancouver Island.
Ed: So for Canada and North America, we're in a unique position because we're located directly on top of a locked and loaded subduction zone fault. So offshore, North America, there's Pacific Ocean oceanic crust, and it's being pushed underneath North America, a process known as subduction. That subduction can lead to giant earthquakes and tsunamis. So there are many other subduction zones around the world. So we're not entirely unique. But for North America, we're certainly very unique.
Jackie: We often hear about California's big one and the San Andreas Fault. But I've learned that the big one that we would be experiencing is from this different subduction course. Would it be more devastating?
Ed: Yeah, so that's a very good question. The answer is probably not very well known. But you're right. So California is actually in a slightly different tectonic setting. The two plates that meet in California are moving side to side. So they're scraping past each other. Whereas the two plates here in what we call the Cascadia subduction zone, so that's from north of Vancouver Island down to northernmost California, the two plates are pushing into each other, and one's being subducted or dragged underneath the other. So it's thought that the Cascadia subduction zone can probably generate larger earthquakes than the San Andreas Fault. So the maximum magnitude of an earthquake in California is probably around magnitude eight, whereas the maximum possible magnitude here in Cascadia is probably more like a magnitude nine. Now, that's only one number difference. But if you remember that this magnitude scale is logarithmic. So actually, a magnitude nine is around 30 times larger than magnitude eight. So that's much bigger. But the good news is that our fault is offshore. So it's about 100 kilometres west of us, and it does angle beneath our feet. So it's not quite correct to say it's 100 kilometres away, but it's not directly beneath our feet. Whereas the San Andreas Fault actually goes right through San Francisco, it goes very close to Los Angeles. So it's right underneath where people live. So what matters for a big earthquake is the magnitude of the earthquake and where the earthquake is located with respect to people.
Jackie: Would that mean that our tsunami risk is higher?
Ed: Yeah, so that's the flip side of the earthquakes that you would expect here, at least the ones on the Cascadia megathrust fault. And those aren't the only type of earthquakes that we might expect here. But those offshore earthquakes because they're located underneath the ocean, whenever there's vertical motion on the fault, so one at one side moves up, and the other side drops down, you get a step in the sea surface, which generates a tsunami wave. The San Andreas Fault is, for most of its length, onshore, so there's no tsunami hazard in California.
Jackie: And this episode, we were talking about an onshore earthquake. Yeah, that's the one that happened in 1946. I know that that one had minimal damage, given that the island population was a lot smaller and there wasn't as much development. But what kind of impact would an earthquake of that size onshore have today?
Ed: Yeah, so it caused a lot of damage. I think a lot of chimneys were toppled even down here in Victoria. It wasn't completely without its tragedy and fatalities. But you're right to say that an earthquake of that size today would be a lot worse because there are so many more people living in the region. Now it was a magnitude seven. So, we talked about eights and nines being the biggest possible earthquakes in California and Cascadia, respectively. So this wasn't as big, but anything above a six is considered pretty dangerous if it's close to people. So a seven is a lot bigger than a six. So this was a 7.2, or 7.3. And the important thing is it was very shallow. So it wasn't deep within the subducting plate of the Pacific Ocean. It was actually here in the North American continental plate. And it is what we call a crustal earthquake. And because they're shallow, they're shallower than the offshore earthquakes that are closer to the surface and have for close to where people live. So they're potentially actually just as damaging as the offshore earthquakes, even though they can't reach those giant magnitudes of sort of 8 to 9.
Jackie: Is that type of earthquake for our area rare?
Ed: That's a very good question. So that's a subject of current intense study. So we're trying to map these thoughts. As we speak, my own research group and collaborators in the US are trying to map out these thoughts. And I can tell you a little bit about the one closest to Victoria because we've done a detailed study and know when it last ruptured. But it's thought that these crustal faults rupture more rarely than the megathrust fault, which is the giant offshore fault. The Cascadia megathrust is known to rupture every few 100 years. The last one was in 1700, so 321 years ago now. So we're inching ever closer to the next one on the Cascadia subduction zone. It might be tomorrow, it might be in 10 years, it might be in 100 years, we don't know. But the crustal faults are thought to rupture on a more like the 1000 year timescale. So, for example, the one closest to Victoria, at least we think, is closest to Victoria, which is what's called the leech river fault. So it goes from near Port Renfrew down through Esquimalt. Lagoon, and then just offshore Southern Victoria. We think that at least this part of that fork closest to Victoria last ruptured about 9000 years ago. So that's a long time ago. But for geologists, that's the blink of an eye. So we consider that an active fault. But it probably doesn't rupture every few 100 years, but every few 1000 years.
Jackie: What kind of damage would that one do?
Ed: I think it would be devastating. I mean, it would depend on the magnitude. If the whole of that fork ruptured in one earthquake, it could easily generate a magnitude seven, maybe even a 7.5. If only a small section of it ruptured, you'd be looking at a six or five and probably a five to six magnitude earthquake would cause a lot of alarm. People would definitely feel it very strongly in Victoria, but it probably wouldn't topple any buildings. But if you go up to a magnitude seven, you're talking about substantial building damage and probably some injuries and fatalities.
Jackie: It does sound alarmist to be saying it could happen at any moment. But realistically, it could happen at any moment, either the onshore or the offshore earthquake.
Ed: I think the key message is that we can do lots of things to prepare for these earthquakes. You can do things in the short term, and there are things we should be doing more. I think, in the long term, certainly, in terms of retrofitting older buildings. There's an adage in our community that earthquakes don't kill people buildings do. And so, there's no reason that a building should fall down when it's shaken. But unfortunately, lots of the buildings, certainly those built before the 1980s, and 1990s, were not built to withstand earthquakes, because, at that time, we didn't know that there were earthquakes in this region, at least, not big ones. So, we can do that in the long term, and we can try and improve the buildings and their ability to withstand strong ground shaking. And then, on a personal level, I mean, we should all have grab-and-go kits and earthquake emergency kits, and earthquake emergency plans. So we know what to do if there's an earthquake, and not all of your family's in one place, and maybe the phone lines are down, and you can't contact each other. So those little things are that you can buy an earthquake emergency kit online in five minutes, or you can build your own one in a few hours. Earthquakes, of course, are not the only hazard that would come in handy. We've all seen the terrible wildfires on the mainland and in the last week or so. And people there had to rush out of their homes in a matter of minutes. And, of course, those who had prepared a grab-and-go pack. We're better off than those who didn't see lots of things that we can all be doing to prepare for the next earthquake.
Jackie: Thank you so much for today.
Ed: Yeah, no problem.