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An Earthquake With a Preliminary Magnitude of 7.8 Struck Off the Coast of Alaska Early Wednesday Morning. (cnn.com) 34

An earthquake with a preliminary magnitude of 7.8 struck off the coast of Alaska early Wednesday morning. From a report: The earthquake was centered 60 miles, or 98 kilometers, south-southeast, of Perryville, Alaska, according to the US Geological Survey. The quake is considered shallow at about six miles, or 10 kilometers, deep. "Anything below 70 kilometers is considered a shallow quake," CNN meteorologist Allison Chinchar previously said. "That's important, because shallow earthquakes often cause the most damage, compared to the ones that are deeper, regardless of the strength." A tsunami warning had been issued following the earthquake, according to the National Oceanic and Atmospheric Administration. The warning was in effect for south Alaska and the Alaska peninsula -- Pacific coasts from Kennedy Entrance, Alaska (40 miles southwest of Homer) to Unimak Pass, Alaska, according to the Tsunami Warning Center. But all tsunami warnings and advisories were canceled early Wednesday morning, according to the National Weather Service.
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An Earthquake With a Preliminary Magnitude of 7.8 Struck Off the Coast of Alaska Early Wednesday Morning.

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  • Headline: Tsunami warning issued
    Article summary: all tsunami warnings and advisories were canceled early Wednesday morning

    Thanks Slashdot

    • I’m sure we will hear about the cancellation in next weeks dupe.
  • ... God just wanted to shake things up a little bit.

    *Tadum* *Crash* *Thud*
    Thank you, thank you, I'm here all week. Try the fish and tip your waiter.

  • Can anyone explain why such a high magnitude, shallow earthquake apparently did not produce a tsunami? TFA says a thrust earthquake is more likely to produce a tsunami, so maybe it wasn't that?
    • Re:Why no tsunami? (Score:5, Informative)

      by bobbied ( 2522392 ) on Wednesday July 22, 2020 @06:52AM (#60318193)

      Because... It didn't..

      Unless you have sufficient vertical displacement in the seafloor and the resulting wave isn't headed in the right direction, you don't get the tsunami. So an earthquake that is deep, or is just horizontal displacement doesn't produce them.

      • Sometimes horizontal displacement triggers massive landslides which in turn trigger vertical displacement. So it’s kind of a very specific incident by incident basis.
    • Can anyone explain why I spilled my coffee today. I use the same mug I normally use, I put in the same amount of coffee that I do every morning. But today I happen to had spilled it, while I haven't spilled my coffee in years.

      A tsunami is a combination of multiple complex systems working together, a tiny variant can change the outcome.

  • Wave Propagation (Score:4, Interesting)

    by necro81 ( 917438 ) on Wednesday July 22, 2020 @07:07AM (#60318223) Journal
    While looking for additional news, I came across this tweet [twitter.com] from IRIS Earthquake Science [iris.edu], an academic consortium for gathering and analyzing seismic data. The tweet includes an embedded video that shows the various waves (P, S, etc.) propagating away from Alaska and lighting up other seismic stations across North America.
  • This is God's punishment for [fill in favorite sin]
  • ... I know the Richter scale is exponential so I can't imagine how terrifying a 7.8 must be.

    • Log 0.8 times more terrifying

      • ...10^0.8 times. Math, how does it work?

        • by danlip ( 737336 )

          Fear does not work on a linear scale, so just converting Richter scale to linear as a fear ratio does not work.

          An analogy is hearing. The decibel scale is logarithmic, but so is human hearing, so doubling the decibels sounds twice as loud even though it is exponentially more amplitude and energy.

        • You just assumed he wanted a linear result...
  • by 140Mandak262Jamuna ( 970587 ) on Wednesday July 22, 2020 @08:57AM (#60318433) Journal
    Very heavy, nearly continuous rains have brought the dam to its design maximum storage. Influx is still exceeding outflow. The water volume is so huge it is actually affecting the rotation of earth.

    Good thing the quake is so far away, but ... still makes one shudder to think what could happen if a quake affects that dam.

    • by danlip ( 737336 )

      "affecting the rotation of earth" is only noticeable because we have atomic clocks and thus can detect a change of 60 nanoseconds per day. That's not a lot. Weather has similar effects.

      • May be there is something to it. Especially in medicine, often the sudden rise in reports of some obscure illness can be traced back to increased testing and better diagnostic methods.
  • ...what's next, is that rain of frogs or river of blood?

    • ...what's next, is that rain of frogs or river of blood?

      Death of every first born, from a virus.

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