71–80 of 149 posts
There’s a nice government’s map that demonstrates potential impact of the various quake scenarios in Seattle: https://experience.arcgis.com/experience/2acb05d732134331bc0... 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
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My mom was a Red Cross nurse who worked in the relief effort after the 1964 Good Friday earthquake and tsunami that devastated Anchorage and areas as far south as Crescent City, California. 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: ht…
Those numbers, while sad, are surprisingly low compared to other causes of death.
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Do you have a source for this? What is "best" in this context?
This is not something with a "source" or a real academic answer. There are too many variables and long tail events. 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…
Everyone in the Seattle region is thinking about earthquakes since we just felt the 4.3 quake on Sunday! https://www.seattletimes.com/seattle-news/environment/small-...
Cascadia Subduction Zone[1] is why I never considered living in Seattle/Portland once I found out about it. Funny, cause I live in the SF Bay Area, where the earthquakes are frequent, but they can never reach the magnitude of what's possible by the Cascadia Subduction Zone. [1] https://en.wikipedia.org/wiki/Cascadia_subduction_zone
The fault is at least 150 miles from Seattle proper, the city will not receive the full brunt of the earthquake. Tsunamis are strongly mitigated by the geography of Puget Sound — the biggest tsunami threat is actually the Seattle fault. By contrast, the San Andreas fault literally runs through the middle of the Bay Area.
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.
Earlier quoted context omitted.
The fault is at least 150 miles from Seattle proper, the city will not receive the full brunt of the earthquake. Tsunamis are strongly mitigated by the geography of Puget Sound — the biggest tsunami threat is actually the Seattle fault. By contrast, the San Andreas fault literally runs through the middle of the Bay Area.
"The fault is at least 150 miles from Seattle proper," 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 o…
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.
Earlier quoted context omitted.
The fault is at least 150 miles from Seattle proper, the city will not receive the full brunt of the earthquake. Tsunamis are strongly mitigated by the geography of Puget Sound — the biggest tsunami threat is actually the Seattle fault. By contrast, the San Andreas fault literally runs through the middle of the Bay Area.
"The fault is at least 150 miles from Seattle proper," 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 o…
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
A particularly crazy thing I learned from some friends who I know who work in this field is that they use underwater hydraulic chainsaws (!) to sample some of these trees. 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)
that 3rd pic could be a black metal album cover
500 error on site, alternative link: https://pubmed.ncbi.nlm.nih.gov/37756412/