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."

So Confused on the GPS Data and Logic

[eldavojohn]

When we look at faults around the world, we see them storing up that energy. So when we first put markers in the ground and measured the position of the Midwestern fault lines we were surprised that we didn’t see any motion at New Madrid. We concluded that there’s no sign that a big earthquake is on the way.

I'm not a geologist so I'm very confused, if something is 'storing up energy' how does moving around equate to that? I mean, if the moving of the ground in violent ways is the releasing of that 'stored energy' then how is small movements indications that it's storing up energy? I would assume that the worse earthquake areas are those when there's a lot of movement going on deep underground but nothing on the surface releasing that energy until a very devastating movement.

So from the Wikipedia article:

The lack of apparent land movement along the New Madrid fault system has long puzzled scientists. In 2009 two studies based on eight years of GPS measurements indicated that the faults were moving at no more than 0.2 millimetres (0.0079 in) a year. This contrasts to the rate of slippage on the San Andreas Fault which averages up to 37 millimetres (1.5 in) a year across California.

Can somebody who knows a lot about this stuff explain to me why we are so sure that a lack of movement in GPS measurements indicate no potential earthquake? My intuition would guess that no movement is not a good indicator either way unless we've figured out how to drive GPS receivers down into the faults themselves and retrieve that information. I think they're just ground stations [nasa.gov] that are taking these GPS measurements, right?

What about the northern earthquakes [slashdot.org]? Do GPS stations up there report tiny movements in the crusts leading up to those earthquakes? I'm just curious if it's possible that you're dealing with different kinds of faults when comparing the San Andreas fault line versus the Ramapo fault line versus the New Madrid fault line.

What we’re learning is that faults switch on and off. They will be active for a thousand years or so, and then inactive for several thousand years. And then other faults may become active. From a scientific standpoint, that’s the really exciting thing we’ve learned from New Madrid. It has been the key to the door that opened up a whole new understanding about how faults inside continents work.

This sounds, at best, questionable or highly fitted to very recent events that we've had the privilege to watch. It's difficult to look over long swaths of time historically when our precision instruments for measuring are a very recent thing compared to the age of the crust. I'm not arguing for the spending of billions in the mid-west but I'm not sold on a single expert's opinion, is this consensus in the geological community?

No, Mostly Missouri

[eldavojohn]

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.

If you look at the map [wikimedia.org], you'll see that the New Madrid fault line is mostly in Missouri and will affect several states further south. It won't even touch Minnesota. Serious earthquakes are pretty rare, even historically [umn.edu] in Minnesota.

I don't know what the winters are like in Missouri and I don't know if many people die from them down there. The threats from poor driving on the road are probably their biggest problems and I don't know if any amount of money will fix that sort of behavior. I grew up near Buffalo Ridge in Minnesota and there were a couple of earthquakes I remember but they didn't leave any visible damage. But yeah there were several ice storms and snowstorms that left us snowbound ... my mom would fill the bathtub full of potable water in case the pipes froze to our well. We had a fireplace as our only heat until I was fifteen when we got a gas heater. Yes, I woke up some mornings to see my breath had frozen to frost on my pillow in front of my face. And there were more than a few nights when I opt to sleep next to the fireplace rather than my bed which seemed to be the furthest away in the house.

Knowing how to survive a bad winter or a hot summer in Minnesota is important but if you look at the area these earthquakes could affect, the area is staggering. I don't know if it would hit quite the population that the San Andreas could but you're talking about a potential large area without utilities, increased lawlessness and a logistical nightmare for support/rescue. It might be worth risking billions to inform people of how to prepare and handle this sort of disaster. I guess that's up to the geologists and seismologists to recommend though.

New Madrid is totally different from Ca faults

[HunterA3]

The New Madrid fault is totally different from the faults in California. The earth in and around the New Madrid fault lines are covered with millions of years of river silt, clay, and other soft strata. It is several miles underground making observation of its activity difficult at best. The most observable activity is the sand boils. They usually indicate pressure pushing up to the surface. The faults in California are within harder, drier strata, making them much easier to see, even with the naked eye. The plates which make up the faults in CA also move with greater frequency causing the strata around them to be splintered with spiderweb cracking, making them easier to move when pressure builds up. The New Madrid fault doesn't move much because it is not along a significant induction/subduction area between plates like those in CA (though the plates on the coast are not actually diving under one another but rather rubbing against each other). This is why the last major quake at New Madrid was so large. There's very little movement to reduce the strain.

"inside-plate" earthquakes difficult to assess

[peter303]

The theory of plate tectonics easily explains the earthquakes at the boundaries of tectonic plates due to the differential grinding motions of these plates. New Madrid is one of the 10%-15% of earthquakes that does not happen a current plate boundary, so its cause is less clear. There are motions of sub-blocks inside a plate. But these are typically an order of magnitude less that at established plate boundaries. So it may take millennia to build the same kinds of strains (20+ feet) it only takes centuries in a place like California. Geophysicists are divided by the amount of strain at New Madrid. Dr. Stein's group only sees a small amount in GPS data. Others see a lot more. The data has noise. Its quality depends on the experimental setup. The more stations you record, the more complexity you see.

The US government and university scientists are spending a lot of money and effort to understand the New Madrid area. It more a lack of understanding of intra-plate earthquakes than the amount of money spent. In this era of "no risk is too small" political correctness (e.g. TSA) perhaps no government authority is willing to demote The New Madrid risk as Dr. Stein claims.

(I was a classmate of Dr. Steins at MIT decades ago,)

Re:New Madrid is totally different from Ca faults

[Me! Me! 42]

Yes. It's surprising that he seems to gloss over this fact (and the physical evidence of many earlier major earthquakes in the area.) I assume the article does not present his argument well. As a geology grad and Illinoian who has experienced tremors in southern Illinois first hand, I will not be one to dismiss the dangers of the New Madrid fault anytime soon. Just two years ago I had pots in my kitchen cabinets rattle from a tremor in the area, and I live 350 miles away, near Chicago. I think his view (as presented) is definitely in the minority among seismologists.

Re:So Confused on the GPS Data and Logic

[Maxo-Texas]

Couldn't a complete lack of movement indicate the area is tightly locked up and it is going to break even more violently?

I thought the historical record showed periodic massive earthquakes every few hundred years. I'd put that over lack of ground movement.

Re:No, Mostly Missouri

[compro01]

The only possibility I can think of that's even remotely like that is wholesale destruction of grain elevators.

How about wholesale destruction of railroad tracks? A strong earthquake will do amusing things [stuff.co.nz] to the rails.