[design219]

I understand that there is debated evidence of large dam projects triggering earthquakes. This makes me wonder if the flooding along the Mississippi river could be a risk for triggering earthquakes. It seems like a silly idea, but water is very heavy and right now there is a sudden, large increase in the New Madrid seismic zone, which is long over due for a big one.

Anyone every heard of such a thing?

[Dork.]

first I've heard of it, could you include some dam links for us?

[design219]

Dam, sure.

Chinese earthquake may have been man-made, say scientists - Telegraph

Top 5 Ways to Cause a Man-Made Earthquake | Wired Science | Wired.com

[ghporter]

When you look at the kind of fault involved in the Chinese quake and compare it to the New Madrid fault system, I think you'll see that there is enough difference to make a New Madrid quake in response to ... well, pretty much anything other than plate tectonics.

It was pretty obvious that there was a fault line beneath where the dam in Sichuan was built, and the dam's size and volume of water it was built to contain were absolutely massive. The current flooding in the U.S., while obviously extremely massive overall, is not applying concentrated weight anywhere. If anything, it's equalizing weight applied in the normal watercourses with the weight of water on areas outside those established channels.

So, while it would be dam stupid to build a humongous dam right over the San Andreas fault, it's no big deal, at least in terms of possible earthquakes, for us to have all this (un) dammed water outside of rivers in the Midwest.

[Dork.]

Thanks for the links! I wasn't finding anything useful with my (quick) searching earlier.

To extend what Glenn said further, at least the current flooding is moving. When dams cause earthquakes, they don't happen right away, they happen over time as the weight of the water behind the dam settles. I don't think the flooding will be there long enough to cause any issues. (Based on the authority I gain from reading up on the subject for five minutes on the Internet, of course.)

[Montezuma58]

Earthquakes in the US have been linked to natural gas drilling. More specifically to the process of "fracking" where water is injected into the wells to release the natural gas. There is not hard proof of the theory but there is a strong correlation between the practice and earthquake activity. I would think that putting a large body of water where there was not one in the past could have a similar effect.

Earthquakes in Arkansas May Be Man-Made, Experts Warn

[ghporter]

Fracking ("fluid cracking" of underground rock structures to release and aggregate trapped gas) does a number of things that are useful for natural gas exploitation. But in a fault zone, it's kind of like playing "how much of the basement wall can we knock out before the floor upstairs sags?" Geologists with oil exploration firms today seem to be capable of taking chances that 20 years ago were unacceptable. Or is it that exploration companies are hiring unimaginative geologists who don't think past the structures they're actively looking at at the moment? Either way, it's a bad thing to break up underground rock if you're anywhere near a fault...

[Dork.]

Yes, Fracking! It's become a much bigger deal here, even since the natural gas industry scientists got shiny new computers, and the estimates of the natural gas under the Marcellus Shale (running through the Appalachians, but exposed in Central New York State) increased by a factor of 100. It's now estimated to be about $200 billion worth of hot air. And fracking is the only practical way to get at it.

Now that people are paying attention, we're trying to decide exactly how much damage fracking can do. We're not all that seismically active here, but there are a few minor faults in the area (something made the Appalachians, after all). But people are not all that worried about earthquakes here, as far as I can tell: they're more concerned with the chemical composition of the fluids used in fracking, and groundwater pollution.

(Maybe we should be more concerned about man-made earthquakes: since we don't get laege quakes here, none of the buildings here are built for it. A quake that California would yawn at would be a doozy here.)

[ghporter]

Fracking near-surface shale is a completely different thing from doing it thousands of feet underground. Is there any sort of fault line anywhere in NY state that has had activity in the last century? Those two things together are important in judging the earthquake risk. Shallow formations are far less likely to cause a serious change in any fault, and really old, inactive faults are far less likely to be affected by anything man-made than active faults.

On the other hand, the fluids used in the process are often nasty. Here in Texas there are suits going on because some drillers used diesel fuel in their fluids, though just plain water can be very effective. I am all for exploiting energy sources at home rather than abroad, but I think there are plenty of petro-explorers who are less interested in long term anything than in short term payoffs. That's bad.

Oh, and I mis-defined "fracking" above. It's "hydraulic fracturing." Same thing, but with the correct terminology.