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Midwest Earthquake Hazard Downplayed
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."
Tectonic plate movement is exceedly slow, and rarely remembers anniversaries.
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...for the release of cataclysm
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.
#fuckbeta #iamslashdot #dicemustdie
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.