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View Full Version : Largest earthquake in 35 years hits Arkansas



RandomGuy
03-01-2011, 11:36 AM
By SARAH EDDINGTON,– Tue Mar 1, 12:07 am ET
GREENBRIER, Ark. – The central Arkansas town of Greenbrier has been plagued for months by hundreds of small earthquakes, and after being woken up by the largest quake to hit the state in 35 years, residents said Monday they're unsettled by the increasing severity and lack of warning.

The U.S. Geological Survey recorded the quake at 11 p.m. Sunday, centered just northeast of Greenbrier, about 40 miles north of Little Rock. It was the largest of more than 800 quakes to strike the area since September in what is now being called the Guy-Greenbrier earthquake swarm.

The activity has garnered national attention and researchers are studying whether there's a possible connection to the region's natural gas drilling industry. The earthquake activity varies each week, though as many as nearly two dozen small quakes have occurred in a day.

"You don't know what to expect. It's unnerving," said Corinne Tarkington, an employee at a local flower and gift shop. "I woke up last night to the sound of my house shaking."

What woke Tarkington was a magnitude 4.7 earthquake that was also felt in Oklahoma, Missouri, Tennessee and Mississippi. No injuries or major damage have been reported, but the escalation in the severity of quakes in and around the small north-central Arkansas town has many residents on edge. Some said they're seeing gradual damage to their homes, such as cracks in walls and driveways.

"We probably had 40 to 50 calls last night," Greenbrier police Sgt. Rick Woody said, noting that the tone of the calls had changed. After pervious quakes, most callers simply wanted to find out if a loud noise they'd heard was an earthquake, he said.

"The fear had calmed down until last night," Woody said Monday. "People's biggest concerns (now) are whether or not these earthquakes are going to get any bigger."

Scott Ausbrooks, seismologist for the Arkansas Geological Survey, said Sunday's record quake was at the "max end" of what scientists expect to happen, basing that judgment on this swarm and others in the past. It's possible that a quake ranging from magnitude 5.0 to 5.5 could occur, but anything greater than that is highly unlikely, he said.

Ausbrooks said he plans to hold a town hall meeting in Greenbrier next month to address people's concerns.

"This quake actually scared folks," he said. "It lasted longer than a lot of the others did."

Ausbrooks said scientists continue to study whether there may be a connection between the earthquakes and local injection wells, where the natural gas industry pumps waste water that can no longer be used by drillers for hydraulic fracturing. Fracturing, or "fracking," involves injecting pressurized water to create fractures deep in the ground to help free the gas.

Geologists don't believe the fracturing is the problem, but possibly the injection wells.

A major source of the state's natural gas is the Fayetteville Shale, an organically-rich rock formation in north-central Arkansas. A six-month moratorium was established in January on new injection wells in the area to allow time to study the relationship — if any — between the wells and the earthquakes.

In Greenbrier, many residents are starting to notice gradual damage. Tarkington said her house has started to show cracks in ceilings and walls.

"You can see the wear and tear on our houses," she said. "I wish they'd go away."

Taylor Farrell, 29, a Greenbrier resident and employee at a local flea market, said a large crack formed in her driveway several months ago, and as the earthquakes continue, the crack has spread into her garage.

She said she and her husband had removed everything from the walls of their house, including family photos and television sets, because many photos had fallen in recent quakes.

"Other than that, there's really not much more you can do," she said. "It's Mother Earth. It's going to do what it's going to do. All we can do is wait for the big one and hope and pray it doesn't happen."

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Interesting bit.

I would imagine that, if there is a connection to fracking, it will become obvious pretty fast, given the natural gas drilling boom.

Wild Cobra
03-01-2011, 11:38 AM
A 4.7?

I think most people would sleep though it, unless real close.

Yawn....

RandomGuy
03-01-2011, 01:26 PM
A 4.7?

I think most people would sleep though it, unless real close.

Yawn....


Some said they're seeing gradual damage to their homes, such as cracks in walls and driveways.

One might not notice the quake itself, but the cumulative damage to real property of minor shifts in the ground would make itself felt to pocket books in a hurry.

Wild Cobra
03-01-2011, 01:32 PM
One might not notice the quake itself, but the cumulative damage to real property of minor shifts in the ground would make itself felt to pocket books in a hurry.

I guess when you live in an area not prone to earthquakes, it makes a difference. Still, had to be pretty close for structural damage, or the buildings were pretty substandard to begin with.

A 4.7 only has 1/20th the energy of a 6.0

Halberto
03-01-2011, 01:54 PM
I can promise you that those natural gas wells are not responsible. The new Madrid seismic zone is the source.

MannyIsGod
03-01-2011, 02:22 PM
The quake was a good deal outside of New Madrid.

johnsmith
03-01-2011, 02:23 PM
A 4.7 only has 1/20th the energy of a 6.0

Cool story.

MannyIsGod
03-01-2011, 02:27 PM
http://upload.wikimedia.org/wikipedia/commons/thumb/9/95/New_Madrid_and_Wabash_seizmic_zones-USGS.png/547px-New_Madrid_and_Wabash_seizmic_zones-USGS.png

The cluster just north of Little Rock is where this quake occurred. As you can see, its well outside of New Madrid.

symple19
03-01-2011, 02:33 PM
Just off the top of my head, isn't this the area where that mega-quake happened in the early 1800's?

MannyIsGod
03-01-2011, 02:37 PM
Several big ones around a magnitude of 8. That kind of a quake now might be the worst disaster in American history. At least San Fransisco and LA have a good deal of preparation for earth quakes. Memphis has none.

symple19
03-01-2011, 02:45 PM
Several big ones around a magnitude of 8. That kind of a quake now might be the worst disaster in American history. At least San Fransisco and LA have a good deal of preparation for earth quakes. Memphis has none.

A good deal of preparation, as well as building codes to ensure everything doesn't come down like a house of cards. Somehow I doubt there are any such codes in this area

RandomGuy
03-01-2011, 03:11 PM
I guess when you live in an area not prone to earthquakes, it makes a difference. Still, had to be pretty close for structural damage, or the buildings were pretty substandard to begin with.

A 4.7 only has 1/20th the energy of a 6.0

That wasn't from ONE quake, but from a "swarm of small ones". The cumulative effect of those small ones would be small, but enough to crack things.

boutons_deux
03-01-2011, 04:08 PM
The NZ earthquake showed that even earthquake-hardened buildings can't withstand a big one.

Cry Havoc
03-01-2011, 04:20 PM
Several big ones around a magnitude of 8. That kind of a quake now might be the worst disaster in American history. At least San Fransisco and LA have a good deal of preparation for earth quakes. Memphis has none.


A good deal of preparation, as well as building codes to ensure everything doesn't come down like a house of cards. Somehow I doubt there are any such codes in this area

It's extremely difficult to prepare homes in that area for an earthquake. The entire Midwest would feel another 8.0. Literally from the East Coast up to Wisconsin would shake, because the ground is so soft in the midwest. The soil there transmits seismic waves with much less loss of energy than in the LA/SF area.

Even the sturdiest house falls apart if this happens: http://en.wikipedia.org/wiki/Soil_liquefaction

A quake at New Madrid would be horrific, particularly if it the epicenter was close to St. Louis.

symple19
03-01-2011, 05:58 PM
The NZ earthquake showed that even earthquake-hardened buildings can't withstand a big one.


It's extremely difficult to prepare homes in that area for an earthquake. The entire Midwest would feel another 8.0. Literally from the East Coast up to Wisconsin would shake, because the ground is so soft in the midwest. The soil there transmits seismic waves with much less loss of energy than in the LA/SF area.

Even the sturdiest house falls apart if this happens: http://en.wikipedia.org/wiki/Soil_liquefaction

A quake at New Madrid would be horrific, particularly if it the epicenter was close to St. Louis.

interesting stuff. let's all hope this doesn't happen anytime soon

MannyIsGod
03-01-2011, 06:26 PM
As I understand it liquifaction needs either water to be present or extremely fine sediment to be present. An example of this taking place would be the 85 Mexico City quake and the Loma Prieta quake. There was damage far from the epicenter that was more severe during the Loma Prieta quake because of this.\

That being said, its not going to do a lot of damage hundreds of miles from the quake from my understanding. It would still be a localized event (I think - I'm not a geologist).

Halberto
03-01-2011, 09:14 PM
The cluster just north of Little Rock is where this quake occurred. As you can see, its well outside of New Madrid.


Don't let that map fool you, all it shows is the concentration of notable seismic events. Zones such as the New Madrid seismic zone have thousands of splay faults that branch out much farther than you would think. We're just now uncovering what the fault system looks like since all we have to go on is shallow seismic reflections and locations of the foci calculated from earthquakes. There aren't many fault scarps at the surface because of accumulation of sediment from the Mississippi River over time and also the nature of the faulting itself (we think that there was a rifting process that failed millions of years ago, the thinned out stratigraphy is now building stress from the divergence in the Atlantic). Concepts from structural geology would definitely argue that the seismic zone is the source.

I'd go into the geophysics aspect of it but that explanation would be lengthy and not worth the time honestly. The creeping foundations would make sense, but not earthquakes.

EDIT: Also, liquefaction occurs from loosely consolidated sediments. Grain size plays a role as well but cementation is just as important. Major river systems = large amounts of weak material = less resistance to particle motion. This is the reason why San Francisco has worse earthquakes that cities outside the bay area.

MannyIsGod
03-01-2011, 09:22 PM
Don't let that map fool you, all it shows is the concentration of notable seismic events. Zones such as the New Madrid seismic zone have thousands of splay faults that branch out much farther than you would think. We're just now uncovering what the fault system looks like since all we have to go on is shallow seismic reflections and locations of the foci calculated from earthquakes. There aren't many fault scarps at the surface because of accumulation of sediment from the Mississippi River over time and also the nature of the faulting itself (we think that there was a rifting process that failed millions of years ago, the thinned out stratigraphy is now building stress from the divergence in the Atlantic). Concepts from structural geology would definitely argue that the seismic zone is the source.

I'd go into the geophysics aspect of it but that explanation would be lengthy and not worth the time honestly. The creeping foundations would make sense, but not earthquakes.

:tu

The Reckoning
03-01-2011, 10:21 PM
all sorts of shit happening in the AR

The Reckoning
03-01-2011, 10:23 PM
Don't let that map fool you, all it shows is the concentration of notable seismic events.




holy shifting rocks batman, we have a jackson school alumnus here :wow



:toast