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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 geograph

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.

btilly 3y ago
Let's see. 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.
- seabrookmx 3y ago
  It's not like the island will just drop into the earth. Unless you were referring the tsunami risk, which is my big fear as a fellow Victorian.
  - btilly 3y ago
    The island does subside in these earthquakes. 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 https://www.mdpi.com/2624-795X/4/3/13 suggest a much milder risk than I had thought.
- djmips 3y ago
  Can you back that up with some references? Very curious, I've never heard any claims that Victoria will end up under water in a big Cascadia earthquake.
  - interloxia 3y ago
    An Ask an Earth-Scientist answer by Dr. Gerard Fryerm suggests a few meters is possible. >"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. http://www.soest.hawaii.edu/GG/ASK/vancouver.html http://www.soest.hawaii.edu/GG/ASK/vancouver.html
    - btilly 3y ago
      It doesn't take a lot of meters to pose a big problem for Victoria, BC. Look at a topographical map: https://en-ca.topographic-map.com/map-1926m2/Victoria/?center=48.43655%2C-123.35561&zoom=13 https://en-ca.topographic-map.com/map-1926m2/Victoria/?cente... That said, https://www.esquimalt.ca/sites/default/files/greater_victoria_tsunami_map.pdf 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.)
lightedman 3y ago
"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 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.
- 01100011 3y ago
  As I understand it, the entire region is on a flat(well, tilted), planar fault because of the way the crust subducts. So you can have earthquakes anywhere in the western PNW from that. 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.
- jandrewrogers 3y ago
  The Seattle fault is a significantly bigger threat to Seattle than the Cascadia Subduction Zone and it doesn’t get nearly as much attention. Parts of the city’s shorelines could subside up to 10-20 feet, and the tsunamis are substantial.

btilly 3y ago

Let's see. 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.

seabrookmx 3y ago
It's not like the island will just drop into the earth. Unless you were referring the tsunami risk, which is my big fear as a fellow Victorian.
- btilly 3y ago
  The island does subside in these earthquakes. 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 https://www.mdpi.com/2624-795X/4/3/13 suggest a much milder risk than I had thought.
djmips 3y ago
Can you back that up with some references? Very curious, I've never heard any claims that Victoria will end up under water in a big Cascadia earthquake.
- interloxia 3y ago
  An Ask an Earth-Scientist answer by Dr. Gerard Fryerm suggests a few meters is possible. >"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. http://www.soest.hawaii.edu/GG/ASK/vancouver.html http://www.soest.hawaii.edu/GG/ASK/vancouver.html
  - btilly 3y ago
    It doesn't take a lot of meters to pose a big problem for Victoria, BC. Look at a topographical map: https://en-ca.topographic-map.com/map-1926m2/Victoria/?center=48.43655%2C-123.35561&zoom=13 https://en-ca.topographic-map.com/map-1926m2/Victoria/?cente... That said, https://www.esquimalt.ca/sites/default/files/greater_victoria_tsunami_map.pdf 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.)

lightedman 3y ago

"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 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.

01100011 3y ago
As I understand it, the entire region is on a flat(well, tilted), planar fault because of the way the crust subducts. So you can have earthquakes anywhere in the western PNW from that. 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.
jandrewrogers 3y ago
The Seattle fault is a significantly bigger threat to Seattle than the Cascadia Subduction Zone and it doesn’t get nearly as much attention. Parts of the city’s shorelines could subside up to 10-20 feet, and the tsunamis are substantial.