3 ms·

> 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 Subducti

> 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. What makes you think a big one ("The Big One") isn't going to hit the Bay Area?

xattt 3y ago
I’m wondering how far the big one will be felt. As egocentric as my question is, will I feel it on the East coast?
- ksenzee 3y ago
  It won’t be _that_ big. They’ll feel it as far as Idaho maybe.
- finite_depth 3y ago
  No, but you would feel it well inland throughout the Mountain West. See this simulated USGS map for a 9.0 quake: https://upload.wikimedia.org/wikipedia/commons/8/80/9.0_Cascadia_scenario_%28median%29.pdf https://upload.wikimedia.org/wikipedia/commons/8/80/9.0_Casc... - for scale, the light blues are about the edge of where you'd clearly go "oh, yep, that's an earthquake", although you might notice such a large one at lower ground acceleration because the shaking would be quite prolonged (~minutes, rather than the ~10-20 seconds of a typical minor quake).
asveikau 3y ago
I don't think they're saying that. 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.
- rapind 3y ago
  Rainier will erupt first and the mudslide will wipe out all those houses built on the last mudslide.
  - seanmcdirmid 3y ago
    Rainier erupting would devastate slot of small communities between it and Tacoma. Like Helen’s blowing it’s glacial too (liquifying into a muddy huge river) but worse since the area around is more populated.
    - rapind 3y ago
      Yes and a lot of these suburbs are built upon the mudslides from previous (recent) eruptions (few million people). Last I heard it was a 1 in 7 chance in my lifetime. It's incredibly stupid and dangerous. Mudslides can travel up to 50 mph or more, and it doesn't even need to be an eruption that kicks it off.
dkasper 3y ago
From what I’ve read the faults in the Bay Area can’t really generate above an 8.0, whereas the cascadia zone can produce much larger events (remember a 9.0 is 10x the intensity of 8.0). It has to do with the size and type of the faults.
- carbocation 3y ago
  Yes: a 7.8 is thought to be the max in the Bay Area, as far as I understand. E.g., https://www.sfchronicle.com/bayarea/article/only-one-bay-area-fault-is-capable-of-producing-a-17767684.php https://www.sfchronicle.com/bayarea/article/only-one-bay-are...
- zamfi 3y ago
  > remember a 9.0 is 10x the intensity of 8.0 10x the ground movement amplitude — 32x the total energy release, though!

xattt 3y ago

I’m wondering how far the big one will be felt. As egocentric as my question is, will I feel it on the East coast?

ksenzee 3y ago
It won’t be _that_ big. They’ll feel it as far as Idaho maybe.
finite_depth 3y ago
No, but you would feel it well inland throughout the Mountain West. See this simulated USGS map for a 9.0 quake: https://upload.wikimedia.org/wikipedia/commons/8/80/9.0_Cascadia_scenario_%28median%29.pdf https://upload.wikimedia.org/wikipedia/commons/8/80/9.0_Casc... - for scale, the light blues are about the edge of where you'd clearly go "oh, yep, that's an earthquake", although you might notice such a large one at lower ground acceleration because the shaking would be quite prolonged (~minutes, rather than the ~10-20 seconds of a typical minor quake).

asveikau 3y ago

I don't think they're saying that. 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.

rapind 3y ago
Rainier will erupt first and the mudslide will wipe out all those houses built on the last mudslide.
- seanmcdirmid 3y ago
  Rainier erupting would devastate slot of small communities between it and Tacoma. Like Helen’s blowing it’s glacial too (liquifying into a muddy huge river) but worse since the area around is more populated.
  - rapind 3y ago
    Yes and a lot of these suburbs are built upon the mudslides from previous (recent) eruptions (few million people). Last I heard it was a 1 in 7 chance in my lifetime. It's incredibly stupid and dangerous. Mudslides can travel up to 50 mph or more, and it doesn't even need to be an eruption that kicks it off.

dkasper 3y ago

From what I’ve read the faults in the Bay Area can’t really generate above an 8.0, whereas the cascadia zone can produce much larger events (remember a 9.0 is 10x the intensity of 8.0). It has to do with the size and type of the faults.

carbocation 3y ago
Yes: a 7.8 is thought to be the max in the Bay Area, as far as I understand. E.g., https://www.sfchronicle.com/bayarea/article/only-one-bay-area-fault-is-capable-of-producing-a-17767684.php https://www.sfchronicle.com/bayarea/article/only-one-bay-are...
zamfi 3y ago
> remember a 9.0 is 10x the intensity of 8.0 10x the ground movement amplitude — 32x the total energy release, though!