fracking and earthquakes

[dreadgeek]

Guihong:

Thank you! I wanted to say something along these lines but lack the knowledge-base you have (my area of expertise is in genetics and bioinformatics) but my *first* thought when I heard about the earthquake was "I didn't know there was a fault line in Virginia" and fracking was a distant consideration. It may be fracking but it seems that, right now and lacking reason to believe otherwise, it is a fairly safe bet to chalk this up to your ordinary, garden variety earthquake caused by the fact that the Earth is still a geologically active place.

Cheers
Aj

Originally Posted by guihong

Fracking is really controversial, no doubt about that.

Here comes my opinion, for what it's worth. My degree is in geology (although I don't strictly work as one), and I've had a petroleum geology, environmental geo, and hydrogeology course.

First, the earthquake today was centered in (what else?) central Virginia. This region seems benign but is really the Central Virginia Seismic Zone, a series of deep and hidden faults that spread like a web from the Appalacians of eastern Tennessee to the coast. These faults, it's thought, originated during the formation of the Appalacians.

This zone has popped before, with earthquakes of similar magnitude as the one today. The reason that earthquakes east of the Mississippi can be felt so far (to Ohio, NYC and Boston), is that the crust is much stronger, is more like a huge sheet, and acts like a conduit for seismic waves. In California, by contrast, the crust is a broken mess and thus seismic waves rattle around in a much smaller area.

A historic earthquake that occurred in 1886 in Charleston, S.C. was the strongest earthquake east of the Mississippi. That one set bells ringing in Boston. That was unrelated to the CVSZ, but no doubt there are other hidden faults from ancient mountain building and crust stretching lurking around.

In Wyoming, I don't know enough where the earthquakes were occurring to say anything definitively but the entire state, and especially the northwest corner, is very active on its own. The Yellowstone area is essentially a volcanic basin with many earthquakes yearly (all, fortunately, small). Given the geologic history of the entire Rocky Mountain area and even the Great Plains, I'd be cautious about immediately blaming fracking for earthquakes.

As for Arkansas, once again this state has been seismically active (but too small to feel) for eternity well before drilling. The New Madrid seismic zone lurks in the northeast corner of the state and likely has many deep and hidden faults tied up with it. At any rate, faults can happen without a major zone nearby, so it's not out of the question that the earthquakes in the central part of the state were natural but not tied to New Madrid or any other faulting.

Don't think I'm defending big oil or fracking-I agree more studies need to be made. In fact, the earthquakes in Arkansas correspond less with the fracking than with the injection wastewater wells, which are much deeper, so that is a major concern. There's also the very real fact that oil and drilling provide good jobs in typically very depressed areas of the country, here in Arkansas and in the Appalacians. What ways can we provide employment and yet not destroy the environment?

I think I agree with you, JAGG, about the environment and preserving it, but until there is more information from sources with no motives tied up with either position, I cannot jump on the "stop fracking" bandwagon.

Thanks for listening to the other side