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Earthquakes

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  • Registered Users Posts: 958 ✭✭✭Conchir


    I read an article recently on the Cascadia Fault in California and preparations for a possible future quake there. Really interesting article, I'd recommend it.

    Anyway, in it they describe how researchers uncovered the last Cascadia quake, from 1700, with a really wide range of evidence. Pretty fascinating I think.
    In the late nineteen-eighties, Brian Atwater, a geologist with the United States Geological Survey, and a graduate student named David Yamaguchi found the answer, and another major clue in the Cascadia puzzle. Their discovery is best illustrated in a place called the ghost forest, a grove of western red cedars on the banks of the Copalis River, near the Washington coast. When I paddled out to it last summer, with Atwater and Yamaguchi, it was easy to see how it got its name. The cedars are spread out across a low salt marsh on a wide northern bend in the river, long dead but still standing. Leafless, branchless, barkless, they are reduced to their trunks and worn to a smooth silver-gray, as if they had always carried their own tombstones inside them.

    What killed the trees in the ghost forest was saltwater. It had long been assumed that they died slowly, as the sea level around them gradually rose and submerged their roots. But, by 1987, Atwater, who had found in soil layers evidence of sudden land subsidence along the Washington coast, suspected that that was backward—that the trees had died quickly when the ground beneath them plummeted. To find out, he teamed up with Yamaguchi, a specialist in dendrochronology, the study of growth-ring patterns in trees. Yamaguchi took samples of the cedars and found that they had died simultaneously: in tree after tree, the final rings dated to the summer of 1699. Since trees do not grow in the winter, he and Atwater concluded that sometime between August of 1699 and May of 1700 an earthquake had caused the land to drop and killed the cedars. That time frame predated by more than a hundred years the written history of the Pacific Northwest—and so, by rights, the detective story should have ended there.

    But it did not. If you travel five thousand miles due west from the ghost forest, you reach the northeast coast of Japan. As the events of 2011 made clear, that coast is vulnerable to tsunamis, and the Japanese have kept track of them since at least 599 A.D. In that fourteen-hundred-year history, one incident has long stood out for its strangeness. On the eighth day of the twelfth month of the twelfth year of the Genroku era, a six-hundred-mile-long wave struck the coast, levelling homes, breaching a castle moat, and causing an accident at sea. The Japanese understood that tsunamis were the result of earthquakes, yet no one felt the ground shake before the Genroku event. The wave had no discernible origin. When scientists began studying it, they called it an orphan tsunami.

    Finally, in a 1996 article in Nature, a seismologist named Kenji Satake and three colleagues, drawing on the work of Atwater and Yamaguchi, matched that orphan to its parent—and thereby filled in the blanks in the Cascadia story with uncanny specificity. At approximately nine o’ clock at night on January 26, 1700, a magnitude-9.0 earthquake struck the Pacific Northwest, causing sudden land subsidence, drowning coastal forests, and, out in the ocean, lifting up a wave half the length of a continent. It took roughly fifteen minutes for the Eastern half of that wave to strike the Northwest coast. It took ten hours for the other half to cross the ocean. It reached Japan on January 27, 1700: by the local calendar, the eighth day of the twelfth month of the twelfth year of Genroku.

    Really good display of different disciplines combining to reconstruct environmental history. The Cascadia fault is 319 years into a 243 year recurrence interval, so a big one is predicted by some geologists, according to the article.

    https://www.newyorker.com/magazine/2015/07/20/the-really-big-one


  • Moderators, Science, Health & Environment Moderators Posts: 5,218 Mod ✭✭✭✭slowburner


    Really cool animation showing the occurence of earthquakes globally since 1901.



  • Moderators, Science, Health & Environment Moderators Posts: 5,218 Mod ✭✭✭✭slowburner


    I'm a little surprised nobody mentioned this one...
    https://www.rte.ie/news/ulster/2019/0430/1046491-donegal-earthquake/


  • Moderators, Category Moderators, Science, Health & Environment Moderators, Society & Culture Moderators Posts: 47,212 CMod ✭✭✭✭Black Swan


    Fathom wrote: »
    Ring of Fire around the Pacific Ocean seems to have more earthquakes lately. What does this mean?

    Per Oregon State University:
    The Ring of Fire is a ring of volcanoes around the Pacific Ocean that result from subduction of oceanic plates beneath lighter continental plates. Most of the Earth's volcanoes are located around the Pacific Ring of Fire because that the location of most of the Earth's subduction zones.

    Plate tectonics are associated with earthquakes.


  • Registered Users Posts: 39,366 ✭✭✭✭Itssoeasy


    Magnitude 6.4 Southern California. I think they said it was 150 miles northeast of LA but it seems it was felt in vegas going on what I've seen on social media.


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  • Registered Users Posts: 39,366 ✭✭✭✭Itssoeasy


    7.1 earthquake in Southern California overnight. The one on Thursday evening is apparently now the foreshock.


  • Registered Users Posts: 2,239 ✭✭✭Jimbob1977


    I was in Ridgecrest about 20 years ago.

    It's slightly outside Death Valley and the population of the surrounding area would be sparse. Desert scrub and small villages.

    The Loma Prieta earthquake that struck San Francisco/Bay Area during the World Series in 1989 was 6.9 magnitude.


  • Registered Users Posts: 39,366 ✭✭✭✭Itssoeasy


    Jimbob1977 wrote: »
    I was in Ridgecrest about 20 years ago.

    It's slightly outside Death Valley and the population of the surrounding area would be sparse. Desert scrub and small villages.

    The Loma Prieta earthquake that struck San Francisco/Bay Area during the World Series in 1989 was 6.9 magnitude.
    Yeah that seems to the only saving grace is that the epicenter is in a remote area. That 1989 one gave TV the greatest opening ever. Having seen the news coverage of it online, the one thing that I found weird(but understandable) was the big difference in the death toll because of the road in Oakland collapsing. I think they say it was over 200 people confirmed dead the day after.


  • Moderators, Category Moderators, Science, Health & Environment Moderators, Society & Culture Moderators Posts: 47,212 CMod ✭✭✭✭Black Swan


    Numerous earthquakes recorded during the past week in California.


  • Registered Users Posts: 5,153 ✭✭✭jimbobaloobob


    Fathom wrote: »
    California "Big One" worries. Check-out paper credible?

    They don't fore see it happening for 3000 according to the article.


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  • Registered Users Posts: 18,996 ✭✭✭✭gozunda


    Fathom wrote: »
    Magnitude 6.0 earthquake
    Affected countries: The Bahamas, British Virgin Islands, Dominica, Dominican Republic, Saint Martin, Sint Maarten, Guadeloupe, Haiti, Montserrat, Puerto Rico, Saint Kitts and Nevis, Turks and Caicos Islands, U.S. Virgin Islands, Caribbean Netherlands, Saint Barthélemy, Antigua and Barbuda, and Anguilla
    45 miles from Isabela, Puerto Rico · Sep 23, 8:23 PM

    The Bahamas really don't need any more disasters after Hurricane Dorian ..


  • Registered Users Posts: 39,366 ✭✭✭✭Itssoeasy


    4.5 magnitude earthquake in California at 10:33pm west coast time(6:33am Irish time) and it was felt in San Francisco and Oakland areas. It's also two days before the 30th anniversary of the Loma Prieta earthquake which for people who lived through the one in 1989 might be a bit eerie.


  • Registered Users Posts: 1,847 ✭✭✭764dak


    Fathom wrote: »
    Wow! Magnitude 7.7 earthquake
    Affected countries: The Bahamas, Cayman Islands, Jamaica, Haiti, Honduras, and Cuba
    87 miles from Montego Bay, Jamaica · 11:10 AM

    It was at 2:10 PM (7:10 PM GMT)

    It was really long too.


  • Registered Users Posts: 5,681 ✭✭✭BumperD


    Fathom wrote: »
    Wow! Magnitude 7.7 earthquake
    Affected countries: The Bahamas, Cayman Islands, Jamaica, Haiti, Honduras, and Cuba
    87 miles from Montego Bay, Jamaica · 11:10 AM

    I am in region affected was nasty enough but no tsunami ( there was a wave that came through but it was small). Minor structural damage (sink holes, cracks, piping, septic tanks ) etc but a reminder that the area is not equipped to handle or prepare for a tsunami all mobile alerts failed


  • Registered Users Posts: 5,681 ✭✭✭BumperD


    764dak wrote: »
    It was at 2:10 PM (7:10 PM GMT)

    It was really long too.

    The 2.10pm is eastern time , 7:10pm UTC. It lasted less than 1 minute. There were 10+ aftershocks last evening one 6.1. One only today of note hopefully that’s the end of it.


  • Registered Users Posts: 5,681 ✭✭✭BumperD


    Fathom wrote: »
    Rock-and-roll. If these are preshocks, the next may be an 8.

    I Really hope not


  • Registered Users Posts: 729 ✭✭✭Granadino


    There have been 100s of earthquakes in the Granada area in the last week, but only 3 of over 4.0. My first experience of them, and a little nervous. There seems to be a regular flow of small tremors throughout the day and night.
    Last Saturday, Tuesday night and last night there were 4.0+ earthquakes. :eek:

    https://www.volcanodiscovery.com/es/earthquakes/spain-portugal.html


  • Registered Users Posts: 729 ✭✭✭Granadino


    Fathom wrote: »
    Mini-shocks to release pressure? Or pre-shocks of a coming big one?

    No idea 🀷*♂️


  • Registered Users Posts: 97 ✭✭zvone


    During Petrinja Mayor Darinko Dumbovic press conference 6.3 earthquake hit Croatia. Half of the town has been destroyed... 7 people died.





  • Registered Users Posts: 369 ✭✭Timmyr


    Fathom wrote: »
    Near New Zealand shakes for itself: 7.3 and 7.4 and 8.1. Tsunami warning!

    What's happening? Plates moving?

    Felt it lastnight, and now we have tsunami warnings


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  • Registered Users Posts: 39,366 ✭✭✭✭Itssoeasy


    M3.3 and 4.0 within 30 minutes of each other in Los Angeles with the 4.0 happening at 4:44am west coast time(12:44pm Irish time).


  • Registered Users Posts: 39,366 ✭✭✭✭Itssoeasy


    Fathom wrote: »
    Continuing speculation about the Big One for LA. Something 8.0 and above. Not if, but when?

    They seem to have been taking about it since the 1994 north ridge earthquake and as you say, having watched several documentaries, it’s not a case of if, it’s when. And there’s been many notable ones since then and thousands of earthquakes that barely register. And what’s different is these two recent ones where in LA not near it.


  • Registered Users Posts: 13,144 ✭✭✭✭cj maxx


    With the Afhanistan earthquake making the news , I had a Google of on earthquakes today. 58 !!. From Alaska ,to Japan, Purto Rico to Argentina. Really lucky in this country

    https://earthquake.usgs.gov/earthquakes/map/?extent=-68.65655,-162.42188&extent=84.9901,-27.42188&map=false



  • Registered Users Posts: 353 ✭✭Daffodil.d


    There's 100s a day. I have an earthquake app on my phone. Just interested in the subject ever since the Pembrokeshire earthquake in the 80s. I was only a child but it woke me that morning. In the south. The app is called volcanos and earthquakes and you can set it to see only the big ones or all of them.. There's also a link within it that tells of activity is low moderate or high. The earth is always grumbling.



  • Registered Users Posts: 13,144 ✭✭✭✭cj maxx


    What do you call the earthquake app,? I might get it. Fairly interested in stuff like this



  • Registered Users Posts: 353 ✭✭Daffodil.d


    There it is



  • Registered Users Posts: 353 ✭✭Daffodil.d


    Good morning, I've been watching my earthquake app and there seems to be a swarm occurring in the reykjanes ridge mid Atlantic region. the last couple of days. Some of the quakes are up to 5.1 on richer scale. I did wonder is it an under sea volcano? Any experts out there got any ideas? Curiosity is killing me because its not something that is always active.

    Thanks in advance.



  • Registered Users Posts: 353 ✭✭Daffodil.d


    No comments yet but they're getting bigger




  • Registered Users Posts: 6,334 ✭✭✭SouthWesterly




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  • Registered Users Posts: 353 ✭✭Daffodil.d


    Big one in the mid atlantic today




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