Multifault earthquake threat for Seattle region revealed by mass tree mortality
science.org
science.org
When we did the study, it was speculated that two of the paleoearthquakes, one on the Seattle Fault and one on another fault on the Olympic Peninsula, could have actually occurred in a single event, but there wasn't much evidence to support this; we consider the magnitude of it on a paragraph at the top of page 1149 but not in the rest of the paper. The recent study (TFA) makes it highly likely that they were part of the same earthquake, but they could be separate earthquakes spaced a few minutes to a few months in time (think of the 7.8 and 7.7 earthquakes in Turkiye this spring, separated by a few hours).
A bit of context about the earthquakes in the Seattle region as well as Cascadia and other areas:
- The earthquakes in the Puget Lowlands and vicinity are relatively infrequent; there are about 15 known earthquakes over the past 17,000 years, and many of them are relatively small (M 6-7). However, they are spatiotemporally clustered[1]: There was a big cluster about 900 AD, and things have been mostly quiescent since then. It can be also shown from the geologic data that at the measurement sites ('paleoseismic trenches'), there haven't been any earthquakes since 17,000 years ago (when the Puget ice sheet retreated) on many of the faults, although the Seattle fault has had a number of earthquakes before.
- The big Cascadia subduction zone events are more frequent (perhaps every 500 years?) and larger, but they may not all be M 9 events, unlike what has been discussed in the famous New Yorker article. That article is based largely on the research of Chris Goldfinger, a scientist at Oregon State University, whose views are credible but on the high side of credible, in the eyes of many other scientists in the region. Many of the earthquakes suggested by the geologic data could be smaller earthquakes (M 7.5-8.5) which won't cause as much ground shaking over such a wide region.
- Earthquakes cause seismic waves at the fault surface, and these attenuate as they travel through the earth towards the surface. The initial magnitude of the waves as the earthquake occurs can be different for subduction zone earthquakes than for shallow earthquakes in the crust, and the attenuation is different for these as well. But importantly, not only are subduction zone earthquakes far off shore, but much of the seismic energy is released deeper in the earth as well, which means more attenuation of ground shaking by the time the waves make it to Seattle.
- A Cascadia earthquake will cause widespread but perhaps moderate damage across the PNW with perhaps, but a strong Seattle fault earthquake will absolutely destroy central Seattle, particularly Pioneer Square and Sodo. The fault comes ashore at Alki Point, for reference. However areas farther away (Edmonds, Tacoma, etc.) will not see nearly as much damage.
- SF and LA both have higher seismic hazard than Seattle[2], considering all earthquake sources, the frequency and magnitudes of earthquakes from the sources, and the seismic ground motions emanating from all of these earthquakes to a site within any of the cities, according to the most recent USGS national seismic hazard model. (See Figure 12 for hazard curves for major US cities).
[0]: https://rocksandwater.net/pdfs/styron_sherrod_bssa_puget_eq_...
[1]: https://pubs.geoscienceworld.org/gsa/geosphere/article/10/4/...
[2]: https://journals.sagepub.com/doi/10.1177/8755293019878199
Out of curiosity, do you have any insight as to the Portland, OR area? We always seem to get glossed over in discussions about the PNW and the West Coast in general.
The seismic risk faced by a city or an individual is really the product of the hazard (formally, the probability of a certain level of ground shaking) and the response of the building stock or other infrastructure. Fortunately, both cities have a large amount of wood-framed housing, which performs quite well in earthquakes (as do modern apartment buildings). However there are a lot of old masonry buildings used for schools, offices, etc. If these aren't properly reinforced, they can be deadly, not only because they are fragile but because they are heavy when they do collapse. But if you live in and work in a modern structure or an old wooden one, you'll probably make it through alright, as long as you have some food and water at home.
The big concern in both cities is actually liquefaction, where some water-saturated soils lose their strength during an earthquake. In both cities, there is some amount of housing stock built on liquefiable soils, but there is a huge amount of commercial and industrial building stock built out on fill dirt on the respective waterfronts (which is where the old masonry buildings are as well). One of the scariests scenarios is the Critical Energy Infrastructure in NW Portland, where massive amounts of oil are in the huge tanks built on fill into the Willamette, liquefying and then spilling into the Willamette/Columbia: https://www.multco.us/sustainability/cei-hub-seismic-risk-an...
They found more exact dates because a massive solar storm in the past changed carbon isotopes worldwide, which is reflected in tree rings that grew during the storm. That's incredibly cool.
https://www.stanleyinfrastructure.com/products/underwater-ch...
The field work in general seems very wet for this kind of research. (my partner did lots of it for her graduate work)
Now one piece adorns my parents new house as the lintel board above the fireplace, and its absolutely gorgeous. I think a some chunks were gifted to an acquaintance who builds guitars, and some more were given to a Salish descended carver.
It was magnitude 9.2, the second largest in recorded history.
The photos she brought back were quite something. I may still have them somewhere, but in the meantime there are plenty online. LIFE.com has a remarkable collection:
https://www.life.com/history/the-great-alaska-earthquake-of-...
https://ready.alaska.gov/_64Quake/History
https://earthquake.usgs.gov/earthquakes/events/alaska1964/
https://en.wikipedia.org/wiki/1964_Alaska_earthquake
From Wikipedia:
> As a result of the earthquake, 131 people are believed to have died: Nine died as a result of the earthquake itself and another 122 died from the subsequent tsunamis all over the world. Five died from the tsunami in Oregon, and 12 died from the tsunami in Crescent City, California.
https://www.census.gov/quickfacts/fact/table/anchoragemunici...
I'll admit that FEMA isn't exactly cited in a way that's possible to corroborate, but presumably they're estimating a worst-case scenario and not a median- or average-case scenario. That might explain some of the large divorce in figures.
There will be lots of damage in Portland. There are lots of unreinforced masonry that will collapse and kill occupants. Most of the bridges, big and small won’t survive cutting off from outside. Infrastructure will be destroyed and utilities will be out of months. All of those could be upgraded which is why Bay Area would be in better shape.
Also, this is talking about Portland and Seattle. Most of the destruction will be on the coast which is closer to the fault. The tsunami will cause lots of damage, destroying most of the towns and killi;g everyone that doesn’t evacuate to high ground.
The 2011 Japan quake is the best comparison but Portland/Seattle aren’t prepared like Tokyo, and there are minimal tsunami defenses.
By contrast, the San Andreas fault literally runs through the middle of the Bay Area.
The Cascadia quake is 100x as big. I'm at 1/3 the distance from the San Andreas fault. Guess who gets the larger earthquake?
Add to that the fact that I grew up in Victoria. All of Vancouver Island is a subduction zone during a Cascadia earthquake. Sadly, that means that a good chunk of what I knew growing up winds up under water. Seattle may fare better, but my home town does not.
Unless you were referring the tsunami risk, which is my big fear as a fellow Victorian.
Reading up now, it looks like it is 1-2 meters, mostly on the west coast of the island. But my memory of the early research when I still lived there in the early 1990s was that it was about a 3 meter drop. Between how low much of Victoria is, widespread poorly build older houses, and lots of housing built on unstable landfill in places like James Bay, my belief was that it was going to be pretty devastating to a lot of parts that I knew.
However recent articles like https://www.mdpi.com/2624-795X/4/3/13 suggest a much milder risk than I had thought.
>"Will part of Vancouver Island "break off and sink," or "split in two at Alberni Inlet?" No. In a big earthquake the seafloor offshore from Vancouver Island will be uplifted and the area along the coast will sink, but at worst that sinking will only be a few meters. If you live very close to the beach and close to sea level then there is a possibility that your house will be flooded, but no big piece of the island is going to break off and disappear. It is possible that there will be submarine landslides along the steepest slopes offshore, but each of those is likely only be small in extent.
That said, https://www.esquimalt.ca/sites/default/files/greater_victori... is built on more up to date information than I had. And suggests that subsidence + tsunami is only 4 meters. Which doesn't pose a serious threat. (If they are wrong and get a 10 meter combination, of course, that would be a far, far worse story.)
Looking at my geological units map of Washington, Seattle is surrounded by a lot of faults, much like parts of Southern California. Some of those much, MUCH closer than 150 miles, and devastating if they go. I can see one going from Port Angeles, crossing the 101, and going into Port Gamble. It likely continues to run either directly under Seattle or just south of it, in fact that might be the continuation of that reverse thrust fault dead south of Seattle which is shown in the map for the story article. If that one goes, Seattle's not having a good time.
But remember, the bay area is also home to many, many faults, and we don't even know the locations of them all. For instance, the next big bay area quake is likely to come from the Hayward Fault in the E. Bay.
I knew a lot of, frankly over-confident people who moved to New England because the news told them it was good for Climate Change. I think the “experts” know a lot less about Climate Change impacts to weather than they want to admit.
Just about a month ago the city next door to me in MA got a freak foot of rain which caused some serious flooding. I had to pump water out of my basement for the first time in years.
Very few places are immune to at least local natural disasters of various types and some of those, like the Vegas area have their own long-term issues.
I’ve been wanting to actually talk about actually solving the problem for decades. But get no takers.
And here, we’re even attacking people just trying to avoid getting run over by the steamroller we insist on not stopping.
It’s crazy.
I posted an Ask HN looking for feedback on where to start trying to do the math and did not really get satisfactory replies. I am wondering if "the industrial revolution" is not really the primary cause of human caused climate change but perhaps largely coincidental. The math needs to get done to meaningfully examine that question.
I'm always wondering how one would foster substantial global wetlands restoration.
I wouldn’t discount measurable increases in global atmospheric co2 either way. And continuing to pump gigatons/yr of ‘new’ co2 into the atmosphere is so unlikely to help the situation, that I’d hesitate to try to downplay it.
The issue with wetlands and forests in this math is that both, generally, are like ‘capacitors’ - except in rare cases, their storage is temporary. It doesn’t (and can’t, if you do the math on volume of space available!) store large quantities of carbon permanently on a geological timeframe. Unless said wetland or forest gets subducted or buried anyway before it rots. If that’s happened though, it drying up isn’t likely to reverse that sequestration.
OPEC currently estimates approximately 70 million barrels of oil are extracted each year (coal far more I believe by volume). Each barrel is 42 gallons. That is just a hair under 3 billion gallons of oil alone. Or 11.3 million cubic meters of oil, per year. Nothing in comparison to the large rivers of the world, but enough to drown most any large city.
It would take a lot of lost wetland by volume to make up for that, especially when you look at cumulative effects over time. Even if the wetlands were pure carbon by volume (hydrocarbons aren’t, but are quite close for a dense liquid!), it isn’t clear there even is or has been that much wetland. That may give you a start though, for the math.
I'm looking for ways to run the numbers to validate a hypothesis that this is a really major factor and also beginning to research mitigation.
But I'm only one person. If I have to figure everything out with no help, this goes nowhere fast.
I added some math to my comment, hopefully it helps.
One way to estimate might be a simplistic, volume/density one. How much carbon is there in the applicable geography/land column? In a forest, it would be the trees themselves (above ground) + the soil. In a wetland, the vegetation + mud/sediment.
There should studies with core samples + samples of vegetation that can give good estimates. Then extrapolate. And you’ll have at least a rough estimate of the potential upper and lower bounds, assuming all that carbon instantly turned atmospheric (or at some assumed rate).
Combine that with numbers like I gave above (I’d do some googling for Coal numbers and add that too), and you should be able to estimate the maximum relative contribution of each source. We’re burning Coal in the billions of tons/yr quantities, and each short ton of coal produces well over a ton of co2 - so that is billions of tons/yr of co2 on its own.
From my profile:
Peatlands cover just 3 percent of the planet’s surface but they store about 30 percent of all land-based carbon, or twice as much as all of the world’s forests combined. Coastal wetlands remove atmospheric CO2 up to fifty-five times faster than rain forests.
I'm not downplaying anything. I'm just seeing data that suggests wetlands loss is a really big deal.
I never remember having heat waves in October or February. We also never needed AC, although maybe I'm just growing soft in my old age.
"Indian Summer" meant things might get a bit warm in September, then cool down. Weather stayed cool until the spring.
This summer has been oddly cool (at least in Berkeley), but got up to 92 2 weeks ago, which is not normal.
When the global average temperature rises some places will get cooler from time to time, there are multiple underdamped systems at play.
Sf gets its water from Hetch Hetche, clean hydro power too.
SF is a very different place in a lot of ways from the rest of California, and the US in general.
https://www.archives.gov/legislative/features/hetch-hetchy/h....
Survival in some of the worst case climate change scenarios involves moving away from the equator where crop failure and extreme heat will occur.
It involves having good access to water, and ideally farmland as wars over resources and refugee migration accelerate.
Martial law of some kind would become a normalized thing in population centers as basic resources and commodities become more expensive. Seattle has a large military presence.
Seattle is positioned geographical well for these things. Being farther north alone is a huge benefit. The mountains of the west due to their proximity to the Pacific enable much more temperate climates than other port cities.
However, the Seattle region is one, and it already has a pleasant temperate climate. IIRC, the main expected change is that it will get more sun in the winter months, which would address the main criticism of Seattle’s weather.
Of course, these models could be wildly off, but to the extent we have such models Seattle is in an enviable position. While there are some regions that look like they will change for the better e.g. some arid regions will get substantially more rain, it is hard to predict the true impact of that change on those regions — that outcome might come with significant trade offs.
What makes you think a big one ("The Big One") isn't going to hit the Bay Area?
10x the ground movement amplitude — 32x the total energy release, though!
But from what I recall reading, the big one that hits Seattle will exceed the big one that hits the Bay. Seattle's big ones are higher magnitude but less frequent. Iirc it's also likely the 9.0 that hits Seattle won't be in most of our lifetimes. The last really big one was before Europeans arrived.
https://www.seattletimes.com/seattle-news/environment/small-...
I can't decide if these are good news making a big quake less likely or foreshadowing of a big quake coming.
There is a lot of research on people not taking possible disasters serious: https://en.wikipedia.org/wiki/Normalcy_bias
Its understandable, but in the end also just noise for those who do and want to discuss mitigiation strategies or statistics. The urge to conjur up security by repeating doubt mighte be huge, but like all prayer, should be kept to oneself.
The media failed to report that the recent quake in Morocco was followed by tens of smaller quakes over the next few weeks, all in a small-ish area that had been quake-free. (In recent memory, at least.)
An interesting observation is that Cascadia Subduction Zone is potentially less devastating than Seattle Fault despite being capable of a 100x bigger magnitude (9+ vs 7.2) thanks to a longer distance from the city
They said this article is the bane of their existence because of people calling into their office with false beliefs that have just propagated into fear over time.
I dont even think the sentence got out of my mouth "so about that article I saw...", I was calling to see if my area was in danger of a tsunami, and she gave relieved my fears greatly.
It will be bad, but also there's a lot more nuance to it.
I picked her brain for about an hour, asking about all different questions about liklihood of tsunami, how far inland, I asked her stuff about my foundation and my house etc.
Id say it would be worthwhile to try and call your local office.
"Great Earthquakes of the Pacific Northwest"
As it turns out, the algorithm does not work in such mysterious ways.
It wasn't until hours later when I checked the news and heard conversations around the office that I realized I had felt an earthquake and just didn't realize it. It had never even occurred to me
I think living in a city I'm just accustomed to a car driving by in a parking garage and various other rumblings so I never considered that's what it was. Later in retrospect, I recognized that being on the 7th floor of a concrete building, nowhere near a parking garage or construction, that was the only explanation.
The most memorable part of the experience was realizing that my unconscious brain recognized it long before I processed it consciously.
In which case they might suggest it to you as well, even if your personal interests are not closely related to whatever happens to be trending?
I don't think it matters or anything but it is an interesting question into virality and where ideas come from.
I was originally watching videos from a guy who goes hiking further north in BC. From there, I searched for similar videos in WA. From there I saw a couple of videos about the modern history (1800's to today) and settlement of Seattle and the sound. From there I saw one of Nick Z's geology videos which I really liked and have been watching them since.