FULL INTERVIEW: UW seismologist breaks down recent earthquakes that shook near Washington, Japan

Added: 2026-05-05

[00:00:00]Yesterday we had an earthquake in Japan.

[00:00:01]Is it similar to the type of earthquake that would happen at the Cascadia subduction zone here, but maybe mirror image of it? It is exactly that. Yes, it's a subduction zone earthquake, so it's on the actual fault between the two plates, just like what we, you know, worry about for the Cascadia megathrust earthquake megaquake. And they had a 7.5 earthquake in Japan yesterday. They've had a lot of aftershocks ever since, and there's some concern.

[00:00:25]Okay, and this wouldn't be considered a megaquake then, right? No, it's not. We They It's the same area, just a little bit north of where the 2011 tsunami disaster came from.

[00:00:35]That one was [clears throat] magnitude nine. So, a megaquake, you know, in our definition is roughly anything above about 8.5 or so, which remembering the scaling is actually a much, much bigger earthquake than a 7.5. Sure, sure, sure.

[00:00:47]What would it be? Like 20-ish, 20 to 30 times stronger? An 8.5 is 30 times stronger in energy released than a 7.5, and then a nine is another, you know, sort of 10 times stronger than that.

[00:01:00]Okay. All right. So, um how bad was the tsunami in Japan?

[00:01:04]Oh, there was only a very tiny tsunami.

[00:01:06]There was no no As far as I know, no damage from it. I think they reported up to 80 cm, so that's about, you know, two two and a half feet uh reported in some harbors. So, fortunately, it didn't create a significant tsunami, and they canceled the tsunami warning relatively quickly.

[00:01:23]Um but there's the the concern that it's possible that an earthquake like this can be a foreshock to a larger one, and then that larger one would produce a damaging tsunami, at least it's a very likely scenario.

[00:01:35]Okay, so how do they jump in and say, "Okay, we went from a 0.1 to 1% chance of a stronger earthquake happening?" Is that just standard protocol?

[00:01:43]Um it's a new protocol in Japan, and we don't have a similar thing here or really anywhere else around the world.

[00:01:49]They've developed some criteria. They have some certain areas of the the subduction zones in Japan that they think um have the potential for a larger earthquake in the, say, coming decades.

[00:02:00]And so, when a magnitude seven or larger occurs inside a particular box, and this was inside that box, then um it's actually more or less automatic that they do this advisory. The advisory is not a prediction of a coming earthquake.

[00:02:14]It just says that based on past experience, there's a higher chance of a larger earthquake than there was before the seven occurred.

[00:02:22]Okay, and the science behind this is just past activity.

[00:02:26]It's past activity both there and and sort of globally. Um you know, there's Every earthquake has a chance of being actually a foreshock to something bigger, but it's quite a low probability. Um but uh in the particular case of the experience in Japan, that one in 2011 was preceded by a magnitude seven earthquake.

[00:02:44]If you remember the um the the earthquake and tsunami warning that came from Kamchatka, from Eastern Russia, last July, uh we had a whole situation with that, and that was also preceded by um uh a whole bunch of early foreshocks, including a seven, and that was a magnitude 8.8, actually the seventh largest earthquake we've ever recorded on the planet.

[00:03:06]Wow. Okay, and the reason why we didn't have anything here, obviously it just wasn't strong enough that far away, right? Very much not strong enough to have affected us here in Cascadia um or in the Pacific Northwest. I will say though that, you know, should a larger earthquake occur, should a megaquake occur in Japan, then that could trigger a long-distance tsunami and tsunami warning like we've seen with some of the others. And that has, in the past, you know, caused damage in Hawaii, in places in the West Coast of the US, from California to Washington and British Columbia.

[00:03:36]Okay, would we be talking what, like a high eight or a nine?

[00:03:39]Yeah, that would be an earthquake at least uh sort of the mid-eights range.

[00:03:43]Yes, I would say if we saw something in the general vicinity of magnitude nine, that's when we really have seen the Pacific-wide tsunamis that that we worried the most about from that that perspective.

[00:03:54]Okay. And then um if we had a magnitude, what was it, 7.7? Yeah, uh 7.5 or 7.7, depending on which system you're counting it on. Yeah. Okay.

[00:04:04]Um if we had something like that on our Cascadia subduction zone, we'd probably have some tsunami activity to it on our coast, right? That is possible, and you know, Cascadia not only has not had a megaquake, but we also offshore in the subduction zone have never even seen a magnitude seven since we've been recording earthquakes for more than 100 years.

[00:04:24]We haven't actually even seen a magnitude six. So, if we had a similar situation on our coast where something like that occurred, we would probably also have to say, you know, the chance of a larger one has now increased. Still not high over the short term, increased.

[00:04:39]And that's why Japan went from 0.1% to 1%. So, you could call that a factor of 10 increase. That's a big increase, but it's still a 1% probability uh in a week. Okay, and if we had a similar Yeah, we would we we would have to do a similar kind of assessment in the US if we saw a situation like this in Cascadia.

[00:05:00]Okay. All right. So, basically, somebody like you or someone else could say, "Okay, we have a heightened risk of earthquakes because we just saw some activity."

[00:05:10]Similar to what A message like that in formal sense would certainly come from the US Geological Survey in consultation with me and my counterparts in Oregon and California.

[00:05:21]Okay. All right. And then uh mid-sevens along the Cascadia subduction zone, is it Can you even say that it would create, you know, potentially 80 cm of water rise? That'd be kind of our our our risk level with this?

[00:05:36]>> [clears throat] >> Yeah, depending on characteristics of the earthquake, um it even a mid-sevens could create a damaging tsunami on our coast. That is not unprecedented. Um it's not a simple just, you know, turn the knob, higher magnitude means higher tsunami, because it depends how much it moves the seafloor, and different earthquakes have different characteristics. So, short version is, yes, even a magnitude seven or 7.5 along the Cascadia coast could produce a tsunami hazard itself. Okay. And then would it behoove us Is it something we should do if we, like Japan, to have this automatic system where if you have activity to automatically upgrade your threat level for new earthquakes in the next how many hours, 24, 48, 72?

[00:06:21]I think we're not quite uh in the same situation as Japan because earthquakes are so frequent there, and they've had so many offshore very large and very damaging earthquakes. So, the same area has had a big damaging earthquake in 2003, in 1968, in 1896, and then of course the 2011. So, um they kind of have a more established scenario. We would have to actually, I think, sit down and really look at what's going on because it would be unprecedented for Cascadia, for the Pacific Northwest.

[00:06:49]Okay. Uh anything else you want to add?

[00:06:52]Uh no, I think that, you know, people, whether they're in Japan or in the Northwest, certainly shouldn't panic at this kind of warning. Um it's a good reminder to make sure you have your evacuation plans ready. If you're in the tsunami area, know how to get away from it. Um and that's exactly what the Japanese government is telling the population there, and I hope that I'm sure they're taking it seriously because people have bad experiences with tsunamis in Japan. Um but hopefully also not, you know, uh overreacting or panicking.

[00:07:19]Okay. And then just one more thing, we'll just hit this again. You know, we had this earthquake across the Pacific.

[00:07:24]We had the tremors along the um Juan de Fuca Ridge. Uh was that one or two weeks ago? This isn't a cause for alarm, but something else may be coming. It's just as likely as it would be without these.

[00:07:37]Yeah, no, nothing about the current activity is an unusual pattern or harbinger of something for the Pacific Northwest. I really want to reassure people that that uh is not anything that we're seeing, and we would certainly be talking about it if we thought it was.

[00:07:50]Okay. Anything else you want to add?

[00:07:52]Uh maybe only just um, you know, with questions about earthquakes or tsunamis, um if you get information and it's coming from social media, the internet, pay attention to the source. You know, look look for the trusted sources like the US Geological Survey or us at the Pacific Northwest Seismic Network.

[00:08:08]Okay. All right, thank you very much.

[00:08:10]All right, thanks a lot, George.