M8.2 Alaskan Quake

[bjdeming]

Event page

The tsunami from this are less than 1 foot thus far, and only some advisories are in effect now. The Anchorage Daily News reports no damage or injuries thus far.



Here's an expert's inside view -- read the whole thread. The USGS aftershock forecast is on the event page.

 

[WesL]

Woke up to this alert and feared the worst. Glad to hear things are good so far.

 

[JayF]

I am glad it wasn't any worse than it was. These are always scary.

 

[bjdeming]

Agreed!

What bothers me, though, is that it occurred near the epicenter of that last biggie, an M7.7, I think. The USGS aftershock forecast for this 8.2 is 3% or less for something bigger in the near future, and no one credible that I`ve read is predicting anything, but I do wonder if these might turn out over the longer -- but still human relevant -- term to be foreshocks of something more along the lines of 1964.

That's inevitable eventually, of course. This part of the Aleutian Trench has been relatively quiet for a while, they say, meaning lots of energy is still stored. Just wish there was a better way to forecast those Really Big Ones. If there is time, will try to read and digest the USGS paper linked in that tweet.

 

[bjdeming]

Strong aftershock last night.

 

[gangstonc]

How do we know it is an aftershock and not a separate event? I’ve always been curious about this.

 

[bjdeming]

That's where the science comes in, I guess: an understanding of the underlying geology and stress fields, which must be very difficult in this complex region of terranes (scroll down to southern Alaska), subduction, volcanism, and so forth. That's probably what the models and experienced seismologists decided it was.

I often wonder how they can tell sometimes, and before the main event, whether big quakes are foreshocks on the next one coming or aftershocks of a prior big one. There's an ongoing situation in Japan that's problematical this way. Can't find the reference right now but will keep looking.

PS: This is what I mean by stress field. Most of the paper is over my head, but it tells me why the Tokyo region is rocking right now. The foreshock/aftershock reference I'm thinking of, though, concerns an area of Japan that's farther north.

 

[gangstonc]

That's where the science comes in, I guess: an understanding of the underlying geology and stress fields, which must be very difficult in this complex region of terranes (scroll down to southern Alaska), subduction, volcanism, and so forth. That's probably what the models and experienced seismologists decided it was.

I often wonder how they can tell sometimes, and before the main event, whether big quakes are foreshocks on the next one coming or aftershocks of a prior big one. There's an ongoing situation in Japan that's problematical this way. Can't find the reference right now but will keep looking.

PS: This is what I mean by stress field. Most of the paper is over my head, but it tells me why the Tokyo region is rocking right now. The foreshock/aftershock reference I'm thinking of, though, concerns an area of Japan that's farther north.

Thank you very much. As an aside, I got to see the Kīlauea eruption in person last week!

 

[Tennie]

Thank you very much. As an aside, I got to see the Kīlauea eruption in person last week!

Did you take any pics? If so, see if you can upload them here to show us!

 

[gangstonc]

Did you take any pics? If so, see if you can upload them here to show us!

I did, but honestly the pictures don’t do it justice.

 

[gangstonc]

 

[bjdeming]

The border between science and art is sometimes a very fine line:

 

[bjdeming]

Gizmodo has a good interview with Alaskan seismologists that ties the recent and earlier 7-pointers near Sand Point with this ~10x larger one in 2021.

There's a problem here, and it's not likely to go away any time soon.

...Alternatively, it could take several more magnitude 7 to 8 quakes—or a single magnitude 9—to release all the stress.

“The societal consequences are very, very different for those two different paths,” West said. Unlike the relatively inconsequential quakes Alaska’s southern coast has experienced in the last five years, a magnitude 9 would be highly likely to produce a dangerous tsunami and damaging ground shaking. Fortunately, “there are, and long have been, very strong preparedness efforts underway in these communities,” West said. “Every community near here has been studied for its tsunami inundation potential.”

That said, “we can always do more education,” he added. “We’ve always got training to do to help people understand how to use that information, and how to do it quickly. You don’t have much time [during] events like this.”