M8.2 earthquake near Perryville, Alaska | Hacker News Reader

M8.2 earthquake near Perryville, Alaska

earthquake.usgs.gov

132 pointswferrell41 comments

First worry is always a tsunami, but in this case it seems like it only generated a max of ~20cm: https://www.tsunami.gov/events/PAAQ/2021/07/29/qwzteb/7/WEAK...

That's what I was wondering, thanks for the info.

However, I wonder if this quake so up north would accelerate the breaking of icebergs.

There's no sea ice that far south at this time of year. Alaska is huge, yo.

Oh, right, I forgot we’re in summer.

There is old joke that if you use metric when announcing a 50mm tsunami, half of Americans will run for the hills. "~20cm" could mean half a foot or 20 hundred meters depending on how much you remember from highschool. Many agencies have policies on how and where metric should be used in public announcements.

fwiw pretty much all unfamiliar americans will associate 'centi' with small, not "hundred"(eth)

Eh we know what a 9mm bullet looks like

Yes, but how many of you reflect over the nomenclature? How many of you know the actual diameter of a "twenty-two" (even if spelled out as .22)? People don't often think about the meaning behind colloquialisms.

American public schools have been using metric for decades. Science classes in American public schools use metric exclusively since the 80s at least. When you meet an American who makes a big deal out of not knowing what a meter is, 9 times out of 10 they're putting on a performative patriotic display mean to get a rise out of you. That, or they're quite elderly.

Incidentally, .22 LR is nominally but not actually 0.22 inches in diameter. It's very slightly bigger than that. In the domain of ammunition, there is often a mismatch between actual diameter and nominal diameter.

With calibers there is a difference between american .22 and european .22. As I understand it, the american measurement is slightly larger as it includes a bit of the rifling groves whereas the European standard was only the bullet width. So the same bullet measures slightly larger on the american scale. Or I might have that backwards, one of the two is different.

https://www.rifleshootermag.com/editorial/comparing-american...

From what I understand, ".22 LR" is nominally .22 inches, actually is .223 inches, and is labeled as 5.6x15mmR in Europe while actually being something like 5.66mm (the 'x15' is the length of the case in millimeters, and the R means rimmed.) They are called different things and both are not quite their nominal sizes, but I think they're interchangeable in practice.

Or 10mm if you’ve wrenched a car

ahh fellow knuckle buster too

People know what the bolt looks like, but the wrench is missing.

It looks like .38SP!

Americans use metric units to measure the size of guns and drug hauls, I think they have at least a minimal understanding of the magnitude...

We got an alert in Jefferson county letting us know specifically that there was no Tsunami.

Could have made the olympic surfing competitions interesting (which they moved sooner because of the storm that passed by)

The Tsunami was in Alaska, not Japan.

You see, they're all connected to the same body of water. And if the tsunami was directional towards the Japanese coast it would've caused issues there.

I think we all know that.

I just don't see how this had anything to do with typhoons and surf contests in Japan, seemed silly.

I guess I didn't get the "joke"

In Japan, TV advisory was extra rough seas (no tsunami) on pacific side throughout the day tomorrow (Friday) as a result of this earthquake.

Here's the big Japanese tsunami that devastated Fukushima arriving in California.

https://www.youtube.com/watch?v=jdMDCLwblkY

I only know this because I clicked on some more stuff after looking at that but the Fukushima tsunami caused a fair amount of damage in the Santa Cruz, CA harbor both to docks and boats. Apparently the waves can get magnified when they go into a narrow channel or harbor. Another thing I only learned today reading the comments of that video is that tsunami literally means harbor wave in Japanese.

https://www.youtube.com/watch?v=_dC_tf4mhO4

Tsunamis from the 1964 Alaska earthquake (M9.2) killed 12 people in California and caused damage in Japan and Hawaii. Tsunamis can travel for a very long distance in open ocean.

Alaska is pretty close to Asia, especially if you look at the great circle distance.

Cargo planes from China, Korea, and Japan normally refuel in Anchorage, and before the extended range of modern passenger jets, most passenger planes also had a refueling stop there.

In 1983, KAL Flight 007, a Boeing 747 passenger airliner en route from New York to Seoul, was shot down by the Soviet Union after departing Anchorage and inadvertently entering Soviet airspace.

The slip patch (where the two tectonic plates slip past each other) of the earthquake did not reach the sea floor, so it didn't generate a big tsunami [0]. If the purple colors in the finite fault map (indicating >2 m slip) reached the trench (the top of the first figure, or the red line in the second), then the earthquake would have displaced much more seawater.

These finite fault maps are made using automated processing of the seismic waves from seismographs around the globe. It's pretty amazing to me that the resolution is so good, from what are not that different than sound waves. These tend to be pretty accurate, not just precise, and are validated from additional studies using different datasets over the subsequent years.

[0]: https://earthquake.usgs.gov/earthquakes/eventpage/us6000f02w...

the two previous large earthquakes in July and October 2020, those previous events were foreshocks of the July 2021 earthquake

A year apart and they're still considered part of the same event. A nice reminder that in geological time, a year is less than an eyeblink.

Seeing the unusual strength of this one, it'll be interesting to see if there's a "quake-walk" around the 'ring of fire' like the clockwise one a few years back.

If you were speaking of a solar power installation you would say, for example, a 300 MW installation -- honoring Watt.

Why, then, a M8.2 earthquake? Why not a 8.2 R earthquake to honor Richter?

Because the magnitude is no longer defined using the original Richter scale. Earthquake magnitudes are now defined using a similar scale called the moment magnitude scale.

Also watts are an SI unit of power, whereas Richters are not a unit of earthquake. It's just the name for the scale itself.

https://en.wikipedia.org/wiki/Seismic_magnitude_scales

Wow. I wonder if any local news station has ever said, "That earthquake with an epicenter in Whittier was a 4.5 on the moment magnitude scale."

Thank you.

Don't they usually say "It was a magnitude 4.5 quake?"

> Whittier

That's the town where everyone lives in the same building right?

No, you're thinking of the little town in Alaska. Whittier is a suburb of Los Angeles -- where Nixon was born, I believe.

Speaking of Watts, is there any way to translate the magnitude M for an earthquake into an equivalent MW of energy?

> Speaking of Watts, is there any way to translate the magnitude M for an earthquake into an equivalent MW of energy?

No, because while if other parameters are the same moment magnitude is logarithmic in energy, the other parameters differ between real earthquakes.

Time so see what Dutchsinse, the earthquake maverick says about this. https://m.youtube.com/watch?v=hhfLTDA8I9g

Pretty interesting, especially when he shows the buoys on the east cost that registered the quake & the plate overlay to show why they felt the quake (because they were on the the other edge of the plate).

Kind of amazing he he managed to put up a 1hr+ video so soon after the quake, ~1.5 hours or so.

Also a bit confusing why the comment posting this video is (as of my comment) getting downvoted? Is this youtuber not considered credible on the topic?

He's got some radical notions but always seems to make pretty good predictions.

For instance, in that video he's calling for a six in Southern California in the next six days.

HAARP?

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