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Earth Science

Seismologist Explains Mexico's Back-To-Back Earthquakes (theverge.com) 50

An anonymous reader quotes a report from The Verge: The second major earthquake to strike Mexico in less than two weeks has caused catastrophic damage in the country's capital. The magnitude 7.1 temblor started at around 1:15PM -- cracking highways, collapsing buildings, and, so far, killing more than 200 people. Less than two weeks ago on September 7th (local time), a magnitude 8.1 quake struck roughly 400 miles southeast from today's. It's not common to hear of such strong earthquakes happening back-to-back so close to one another, says John Bellini, a geophysicist with the U.S. Geological Survey. "Usually you don't have large ones in the same general region right away," Bellini says. "But in highly [seismically] active regions of the world, it can happen."

Mexico qualifies as highly active. The country sits at the boundary of three pieces of the Earth's crust that fit together like a jigsaw puzzle -- called tectonic plates. Today's quake originated on a fault within the Cocos plate, which is on Mexico's western edge. "Whether or not faults rupture depends on the kind of stress that builds up," Bellini says. The Cocos plate scoots rapidly under the continental crust of the North American plate, which "builds up the stress and strain at a faster rate," Bellini says. "So you're liable to have more frequent earthquakes because of that." Mexico City is especially prone to severe damage because of the ground it sits on -- an ancient lakebed that quivers like jello, Bellini says. When earthquake waves pass through it, it jiggles, magnifying the vibrations. "So the reason that Mexico City seems susceptible to more damage is because of this amplification effect of the lake bed," Bellini says.

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Seismologist Explains Mexico's Back-To-Back Earthquakes

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  • PROOF! (Score:2, Funny)

    by Anonymous Coward

    Climate Change Is REAL!

  • Experiencing a little turbulence in our solar orbit.
  • by Anonymous Coward on Wednesday September 20, 2017 @05:46PM (#55234473)

    Why do we, as a society, continue to pay enormous amounts of resources to rebuild in places such as Mexico City, New Orleans, Houston, etc? These places are proven by science to be horrible places to build infrastructure. Yet the same people who argue we should spend tax dollars rebuilding for the people that continuously ignore nature/science and rebuild in places like this, also cry that we need to spend more money to prevent human caused global warming? Someone please explain this hypocrisy to me.

    • by cogeek ( 2425448 ) on Wednesday September 20, 2017 @05:56PM (#55234559)
      It's worth it to keep rebuilding just to keep them from moving to Colorado. No earthquakes, hurricanes, tidal waves, quick sand. Just the occasional tornado and blizzard. Err, I mean Kansas, not Colorado. All you Californians, keep on driving till you hit Kansas. It's REALLY safe there.

      But seriously, there's natural catastrophes anywhere. Colorado is considered safe for datacenters etc, but we have flooding, tornadoes, blizzards. You could make the argument that humans shouldn't build infrastructure anywhere because it's not safe.
      • by Anonymous Coward

        You could make the argument that humans shouldn't build infrastructure anywhere because it's not safe.

        Or we should REPLACE THE EARTH with something safer.

    • by Solandri ( 704621 ) on Wednesday September 20, 2017 @06:20PM (#55234709)
      • New Orleans sits at the mouth of the Mississippi, which provides transport by cargo ship to/from about half the inland U.S. cities
      • Houston is the west-most major U.S. port in the Gulf of Mexico, providing access to the western half of the U.S. for cargo offloaded from ship to land. Ironically, that role used to be filled by Galveston (which used to be bigger than Houston). Until a hurricane in 1900 [wikipedia.org] wiped out most of Galveston and people decided it was safer to move further inland to Houston.

      They may be horrible places to build in terms of natural disasters, but they are very advantageous places to build in terms of economics. Economics affects our lives every day. Natural disasters affects our lives once every few decades.

      Mexico City is built on an ancient lake bed. That makes the ground very flat, which again is economically advantageous when building infrastructure (you can construct it cheaper). That lake bed is also what makes earthquakes there so bad [wikipedia.org].

      If you eliminated all places on Earth where natural disasters could cause lots of damage (earthquake, hurricane, tornadoes, flood, wildfire, drought, avalanche/landslide, volcanoes, tsunami, heat waves), there would be precious few places on the planet where you could build a city. So you build in whatever places are economically and socially advantageous, and deal with the natural disasters when they happen.

      • They may be horrible places to build in terms of natural disasters, but they are very advantageous places to build in terms of economics. Economics affects our lives every day. Natural disasters affects our lives once every few decades.

        Mexico City is built on an ancient lake bed. That makes the ground very flat, which again is economically advantageous when building infrastructure (you can construct it cheaper). That lake bed is also what makes earthquakes there so bad.

        The flaw in your argument is this: Wh

    • I think a better question is why do we continue to build so stupidly. And the answer is usually corruption. You can build structures that can withstand these kind of quakes. California (for example) has done a lot of seismic retrofit work to keep buildings up in case a major earthquake hits, let alone to renovate buildings damaged by quakes such that they won't suffer the same fate again. Mexico needs to do the same kind of thing if they're going to avoid suffering the same fate repeatedly.

  • We might as well say it [pinimg.com].

  • by Anonymous Coward

    There haven't been any aftershocks within 100 miles of the 7.1, not a single one.

  • World's ending Saturday.

To err is human, to moo bovine.

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