Geologists say fault in central Ark., site of hundreds of earthquakes, is longer than thought

Geologists say fault in central Ark., site of hundreds of earthquakes, is longer than thought

www.therepublic.com

LITTLE ROCK, Ark. — Geologists say a fault in central Arkansas where hundreds of earthquakes have been recorded in recent months is longer and potentially more destructive than initially believed.

Scientists had thought the fault is 3.7 miles long. Now they estimate it to be 6 to 7.5 miles long.

Arkansas Geological Survey geohazard supervisor Scott Ausbrooks told the Arkansas Democrat-Gazette that the length is a concern because a longer fault could trigger bigger earthquakes.

More than 800 earthquakes have been recorded in the area in the past six months — including a 4.7 magnitu

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So now scientists are saying the fault line in central Arkansas is twice the size they thought it was. Adding of course, to Arkansas' worries.

But a few questions stick out in my mind.

Was their first estimate based on observation, or guesstimates?

And depending on the answer to that question...have the swarm of recent quakes made this fault longer than it was?

Or has it always been this size, and they just figured that out?

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ETA: From Arkansas Online...

Geologists say a previously unmapped fault that is the source of a swarm of earthquakes around Guy and Greenbrier in Faulkner County is longer and potentially more destructive than they initially believed.

Prompted by growing knowledge of the fault, the Arkansas Oil and Gas Commission last week ordered a halt to operations at two disposal wells in Faulkner County that commission staff think might be linked to the seismic activity.

The injection wells operated by Chesapeake Operating Inc. and Clarita Operating LLC contain discarded fluid used to drill for natural gas in the Fayetteville Shale. In the five days since the injections were stopped Thursday, the number of the biggest quakes - those over magnitude 2.5 - has decreased in the ...

reply to post by Klassified


Very good questions indeed. I would say that they just guessed. If they mesured it they would have known it was bigger. Unless of course like you said the recent swarms made it bigger. But im not sure if that can happen or not. I dont know a lot about quakes and fault lines. I have just recently started researching them. Nice find though!

Not much to back this up at the moment. When they give a report its just so cut and dry, it irritates me. They should have included more information on how they know this and a map showing the fault line as it is.

I'm still digging for more info. But it seems to be a rare commodity at the moment.

I'm thinking True American and Puterman might be helpful on this one.

ETA: This is on USGS from February of this year, but I'm not sure how much help it's going to be.

USGS Arkansas...

Still digging...

I was wondering if there were any maps with all these Fault lines?

Considering the intense political pressure many USGS scientists have had to face when discussing potential threats to local populations, I wouldn't be surprised if their initial estimates were "best case scenario" so as not to interfere with development plans and other such considerations which local politicians (read businessmen) normally care about.

If the USGS could have been mistaken about this fault line; could they be wrong about others? Somehow I am disinclined to believe they measured it in the first place. How can a mistake of that magnitude be justified? TWICE as large? That's a game changer.

reply to post by Maxmars


I would agree, except for the fact that this is a pretty short fault anyway. Bearing in mind the geology of the area it probably is quite difficult to determine where a fault lies if all you have to go on are buried sand blows!.

To the other poster: I can't find a fault map anywhere yet.

reply to post by Klassified

Was their first estimate based on observation, or guesstimates?

And depending on the answer to that question...have the swarm of recent quakes made this fault longer than it was?

Or has it always been this size, and they just figured that out?

My questions too - PLUS - when was this fault "discovered"? ...is it possible that it only formed just recently?

S&F&

reply to post by soficrow

This particular fault was discovered in 2009 from what I've read so far.

reply to post by Klassified


Hmm. Sounds a bit ...revealing.

If it was older it should have been discovered sooner than 2009, dontcha think?

Geologists at the Arkansas Geological Survey say the current Greenbrier-Guy swarm is giving them a clear picture of a fault they never knew existed.

Geohazard Supervisor Scott Ausbrooks says they used to believe the fault ran about six kilometers from Greenbrier to Guy. But recent seismic activity has Ausbrooks thinking the fault is closer to 12 kilometers in length, raising the magnitude of a potential earthquake from 5.0 to 6.0.

arkansasmatters.com...

I pretty much already gave an opinion on this here:

www.abovetopsecret.com...

As mentioned, my concern is probably more for any unknown additional extensions to this fault, which could bring total fault length to longer than 12 km- meaning it might not stop at 6.0- could be larger. Remember, the east is very sparsely mapped, so there are a lot of unknowns.

The lack of information and previously inactive unknown faults is the source of much discovery. The major "tip-off" for me was when I read about Dr. Haydar Al-Shukri's page, of UALR, which describes "Sand Blows."

There is many sandy places, in rural areas, in the "Eastern Arkansas" region. There was an earthquake, in the mid-1970's, which measured approximately in intensity as the recent Greenbrier, Arkansas quake. I remember that one being very short-duration of 1 to 2 seconds, or less and with more horizontal motion than Greenbrier's.

Greenbrier's quake felt like a rumble or wavefront, which hit and pitched-downward after the initial impact and lasted approx. 3 secs. here at home, but reports of "tables walking across the floor," "sofas moving away from the wall," and the rumbling lasting 20 to 30 seconds are typical. There's a 3-D map somewhere of the underlying "layers" of the Mississippi River Valley, I'll try to find a copy.

reply to post by TrueAmerican


I agree, and say to follow the swampy areas and dried-up creeks and streams. Arkansas is a treasure-trove of topographical formations which jump-out, especially when you overlay terrain with recent event's locations. Some are hidden, especially in the Delta Region, but starting at the Marianna fault and working upward along the L'anguille River westward is a good bet. Those swampy areas around Brinkley and De Valls Bluff heading upto Beebe are worth a look too.

reply to post by trekwebmaster


Thanks for the information and I am
looking forward to a map if you find one.