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Science

Midwest Earthquake Hazard Downplayed 96

Posted by kdawson
from the whole-lotta-shakin dept.
swellconvivialguy writes "Next year marks the bicentennial of the 1811-12 New Madrid earthquakes, with earthquake drills and disaster tourism events planned across the Midwest, including the Great Central US ShakeOut. But despite the fact that Earthquake Hazard Maps equate the New Madrid seismic zone with California, geologist Seth Stein says new science (especially GPS data) tells us that the hazard has been significantly overestimated, and that we should not spend billions on earthquake preparations in the Midwest."
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Midwest Earthquake Hazard Downplayed

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  • Fortunately, (Score:5, Insightful)

    by Samantha Wright (1324923) on Monday November 22, 2010 @09:33AM (#34305580) Homepage Journal
    Tectonic plate movement is exceedly slow, and rarely remembers anniversaries.
  • bold (Score:2, Insightful)

    by symes (835608) on Monday November 22, 2010 @09:34AM (#34305608) Journal
    It is a bold man that tells people that they shouldn't take out insurance - and even bolder given the level of uncertainties there are in seismology. That said, IANAS.
  • Just in time... (Score:3, Insightful)

    by Anonymous Coward on Monday November 22, 2010 @09:41AM (#34305682)

    ...for the release of cataclysm

  • by girlintraining (1395911) on Monday November 22, 2010 @09:43AM (#34305708)

    Money would be better spent making a few places secure for winter time emergencies. Unlike California, if we're without power or housing, we die.

  • Re:bold vs. coward (Score:3, Insightful)

    by somaTh (1154199) on Monday November 22, 2010 @10:01AM (#34305912) Journal
    I'm confused. Are we talking about midwest earthquakes or terrorist plots?
  • Re:bold vs. coward (Score:3, Insightful)

    by robot256 (1635039) on Monday November 22, 2010 @10:17AM (#34306100)
    The terrorists are plotting an earthquake! Everybody panic!
  • Dark magic (Score:3, Insightful)

    by gmuslera (3436) on Monday November 22, 2010 @10:29AM (#34306250) Homepage Journal
    That comment from the geologist looks like the perfect way to summon the Murphy undergod. May be it wouldnt was to happen anything bad before, but now the resulting megaquake will even trigger the Yellowstone supervolcano.
  • by rrossman2 (844318) on Monday November 22, 2010 @10:49AM (#34306510)

    In my mind I'd see it more like trying to remove a pressed wheel bearing. For example I have an OTC Hub Tamer Elite that has a C shaped part you put between the knuckle and the hub/rotor assembly, and then a J shaped piece that goes off of the C and ends up on the other side of the knuckle aligned with the hole in the wheel bearing. You put a long high strength bolt down the middle of the wheel bearing and into a disc, and then put a nut on. You hold the nut, and use an impact to drive the bolt. The bolt can't move inward any because of the J part, so the nut forces the disc to push the hub and/or wheel bearing out. Sometimes on a really stuck wheel bearing, the impact is giving all it's got but nothing is moving, and you're now maxing out what the 500 lb/ft impact can do. The movements near the end of tightening it as far as it can go are really, really small, but man there's a lot of pressure on the nut, bolt, and bearing. In that situation, you just take a hammer and smack the J once, and it that bearing comes flying out, and I mean flying. So in *my* mind, a lot of movement would mean there's possibly not as much pressure between the two, which is allowing it to move faster, where as the slower movement would possibly mean increased pressure and that's why the movement is so small.

    Either way I'm not a geologist or a seismologist or whatever, so what do I know :)

  • Seismologist, here (Score:5, Insightful)

    by Anonymous Coward on Monday November 22, 2010 @12:30PM (#34307756)

    Seismologist (in training -- Ph.D. student), here.

    The scientific and engineering consensus is that there is an earthquake hazard in the central US. New Madrid had three massive events at around ~M8.0 200 years ago, a dozens of M6.0 events, and there is paleontological evidence showing that these earthquakes have occurred every few hundred years dating back quite some time. The USGS gives the New Madrid seismic zone a 25-40% chance to have a M6.0 or larger earthquake in the next 50 years. I might note that seismic waves in this area travel significantly farther due to the older, less smashed-up ground underneath this region of the country. Additionally, the New Madrid seismic zone is filled with up to 1km of thick sediment. How, exactly, seismic waves propagate through thick sediment is still undergoing much study, but we do know that they focus earthquake energy, and studies in Taipei have shown that sharp velocity gradients in the sediment can double the peak ground acceleration of an earthquake at the surface.

    Seth Stein and a few others in the GPS area look at surface measurements as the only sign for strain to build up causing an earthquake. This works with very pretty models of earthquakes, like near San Andreas and Eric Calais' famous "Haiti prediction" (he looked at the strain rates, calculated how much strain had built up since the last earthquake, and stated that if an earthquake were to happen soon, it'd be ~M6.8 or so), but it breaks down significantly for inter-continental seismic zones. The New Madrid seismic zone is one of those zones, and it is poorly understood. However, it doesn't take brain-busting thinking to entertain the idea that strain rate at the surface doesn't mean that nothing is happening at the subsurface, and, in fact, the New Madrid seismic zone has very frequent small magnitude earthquakes every day.

    The scientific consensus is that the New Madrid seismic zone presents a serious seismic hazard based on tons of historical evidence and current seismological research. Seth Stein is the devil's advocate to that view and frequently and very public tells the world that there will never, ever be another big earthquake in New Madrid, ever. He is in the minority.

    I might note that seismic hazard assessment for Wenchuan, China, was rated very highly in the 1950s due to historic evidence of horrible earthquakes in that area. Since the 1950s, the Chinese seismic hazard map has been revised several times and, due to very very slow strain rates measured by GPS, Wenchuan's risk of a catastrophic earthquake was downgraded to basically negligible. In 2008, however, we all saw that massive M7.9 that struck and killed so many people in this area where strain rates were "too small for a large earthquake."

    I also might note that physicists at USGS have used the very same data that Seth Stein collected and used, and when they subtracted out the average movement of the North American continent, they found strain rates in the central US that were very high, more than enough to create a catastrophic earthquake. There is more than one way to interpret Stein's data.

  • by vlm (69642) on Monday November 22, 2010 @12:31PM (#34307782)

    Inputs : Agribusiness works on diesel, damaged pipelines, etc. No fuel / seed / fertilizer / bug spray adds up to big problems.

    Scale : One tipped over combine harvester is no big deal for the village's single tow truck and the villages single mechanic, and the regional tractor distributor probably has "a" spare part in stock. And his neighbor is probably friendly and OK. On the other hand, when ALL the harvesters / tractors in one area tip over or are crushed by collapsed barns etc, then we all have a big problem.

    Time : Agriculture is pretty time sensitive, you can't just decide to plant or harvest next month on a whim. General mayhem could very severely impact crop yields simply by giving the survivors something more urgent to do at just the wrong time. Many crops only survive by irrigation, which is great if you have either electricity or diesel, not so great if the supply chain is interrupted for a couple days.

    Output : No star trek transporters. Need working railroads, which means working phone lines and working electrical grid and no trees across the (twisted?) rails. Or you can do the diesel truck thing, which also requires truck driver infrastructure like staffed and full gas stations. The river will continue to work, assuming you can reach it.

"If that makes any sense to you, you have a big problem." -- C. Durance, Computer Science 234

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