Swarm of 800 Earthquakes Have Struck North Central Arkansas Since September 2010

Locals Unsettled by Intensifying Earthquakes after Largest Quake in 35 Years Hits Arkansas

Residents of the small north-central Arkansas town of Greenbrier say they are unsettled by the fact that they never know if or when the next earthquake is going to strike

March 1, 2011

AP – 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."

Beebe, Arkansas, the town were 5,000 red-winged black birds fell from the sky around 11 p.m., Friday, December 31, is not that far from Pine Bluff, where the U.S. Army maintained a chemical weapons arsenal for more than 60 years; it began disposing of the stockpile in March 2005 and completed disposal operations in November 2010. The spot along the Arkansas River where the 100,000 drum fish were found dead on Thursday, December 30, was near Ozark, Arkansas. The community of 549 residents, Guy, Arkansas, which has experienced an almost constant shaking from 487 earthquakes since September 20, is north of Little Rock. The Arkansas River runs along Little Rock and Pine Bluff. There is an U.S. Air Force base in Little Rock.

Natural Gas Drilling Might be the Cause of Arkansas Earthquakes, Geologists Say

According to the Arkansas Geological Survey, this is the largest quake outside of the New Madrid fault system since 1969

February 28, 2011

KSPR-TV - The question many have Monday, is why would a 4.7-magnitude earthquake strike outside of the New Madrid Fault System? According to the Arkansas Geological Survey, this is the largest quake outside of the fault system since 1969.

"There's been a whole bunch of more earthquakes, just recently, in this region up in here, just north of Little Rock," says Mickus.

Geologists have a guess.

"There's a whole bunch of natural gas exploration there. They inject fluids there, and that's been shown to kind of lubricate faults and case small magnitude earthquakes," says Mickus.

But, the natural gas wells are not drilled nearly as deep.

"The wells only 3,000-5,000 feet down and the earthquakes are one to three miles down," says Mickus.

So, any actual explanation? Your guess is as good as Mickus's.

"There's nothing much tectonically going on here. So, no. That's a good study. It's a good thesis," says Mickus.

Mickus says, without an actual study, there's no way to be sure the natural gas drilling is causing earthquakes. A study can cost millions of dollars.

Earthquake 'Swarm' Rattles Arkansas Town and Its Residents

December 13, 2010

CNN - The Arkansas Geological Survey is trying to unravel a mystery: What is causing earthquakes in the town of Guy, Arkansas?

Since September 20, the community of 549 residents north of Little Rock has experienced an almost constant shaking from 487 measurable earthquakes.

"We've had 15 today including a 3.1 (magnitude) from this morning," Scott Ausbrooks, geohazards supervisor for the Geological Survey, said Monday. "These are shallow quakes between two and eight kilometers (between one-and-a-quarter and five miles) below the surface."

While earthquakes aren't unusual in the Southeast state, the frequency is.

"This time last year we had 39 quakes total for the entire state," said Ausbrooks.

Most of the quakes in the swarm -- a localized surge of earthquakes with all of them about the same magnitude, according to the United States Geological Survey -- are so small they go unnoticed. The largest, a 4.0 on October 11, caused the only documented damage, cracking a window at a visitor's center to a state park.

Guy Mayor Sam Higdon said when the swarm first happened, citizens took notice.

"They were calling City Hall asking, "What are you going to do?'" he said.

In response to the constant bombardment of tiny quakes, Higdon's office has organized a three-hour long town meeting, and sought the help of state geologists and members of the oil and gas industry to find answers.

"My wife wants to buy earthquake insurance. I'm trying to talk her out of it," the mayor said Monday.

There are several geologic faults in the area, but none associated with the New Madrid fault, the large seismic fault in the region and one that was the source of an estimated 7.0-magnitude earthquake in 1811. And there was another historic flurry of earthquakes in 1982, 15 miles south of Guy. Geologists know it as the Enola Swarm, responsible for 15,000 quakes within a year's time, followed by more shaking in 2001.

At first, town officials assumed the current wave of shakes came from work at a gravel company on the outskirts of town.

Ausbrooks says the state Geological Survey has no idea whether the current swarm is a natural or man-made event, but his office is seriously exploring the latter.

"We see no relation to the drilling in the area, but we haven't ruled out a connection to the salt water disposal wells," he said.

According to the Arkansas Oil and Gas Commission, there are at least a half dozen "disposal wells" within a 500-square-mile zone around Guy. Licensed by the state of Arkansas, disposal wells are a byproduct of the oil and gas industry and are used to inject drilling waste water back into the earth after drilling.

Ausbrooks said drillers inject waste water into the earth at high pressure, and in the area around the town the disposal wells go as deep as 12,000 feet. He points to incidents in Colorado in the 1960s at Rocky Mountain Arsenal, where deep water injection was tied to earthquakes.

Last week the state of Arkansas issued a moratorium on new drilling permits. Lawrence Bengal, director of the Arkansas Oil and Gas Commission, said previously his office required only monthly reports outlining the operations of injection wells.

"We're asking well operators to provide daily reports now," Benegal said.

Ausbrooks said his office is pouring over the data trying to determine whether there is a correlation between the disposal wells and the shaking, and he hopes to present preliminary findings to the state next month.

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Latest Earthquakes Worldwide and Earthquake News

News Blogged - Below are the latest earthquakes and earthquake news from around the world from February 28 - March 1, updated in real-time by RSS feeds, latest news is lower down the page below the latest quakes!

USGS M 2.5+ Earthquakes

Real-time, worldwide earthquake list for the past day

M 3.5, Arkansas
Tuesday, March 1, 2011 16:03:05 UTC
Tuesday, March 1, 2011 10:03:05 AM at epicenter
Depth: 5.10 km (3.17 mi)

M 3.3, Arkansas
Tuesday, March 1, 2011 15:58:46 UTC
Tuesday, March 1, 2011 09:58:46 AM at epicenter
Depth: 5.60 km (3.48 mi)

M 4.3, Kodiak Island region, Alaska
Tuesday, March 1, 2011 15:12:50 UTC
Tuesday, March 1, 2011 06:12:50 AM at epicenter
Depth: 15.30 km (9.51 mi)

M 4.4, offshore El Salvador
Tuesday, March 1, 2011 14:56:56 UTC
Tuesday, March 1, 2011 08:56:56 AM at epicenter
Depth: 60.50 km (37.59 mi)

M 5.1, Mariana Islands region
Tuesday, March 1, 2011 14:05:59 UTC
Wednesday, March 2, 2011 12:05:59 AM at epicenter
Depth: 44.20 km (27.46 mi)

M 5.4, Rat Islands, Aleutian Islands, Alaska
Tuesday, March 1, 2011 12:50:00 UTC
Tuesday, March 1, 2011 02:50:00 AM at epicenter
Depth: 47.70 km (29.64 mi)

M 2.7, Mona Passage, Puerto Rico
Tuesday, March 1, 2011 12:17:32 UTC
Tuesday, March 1, 2011 08:17:32 AM at epicenter
Depth: 56.80 km (35.29 mi)

M 2.5, Southern Alaska
Tuesday, March 1, 2011 12:16:26 UTC
Tuesday, March 1, 2011 03:16:26 AM at epicenter
Depth: 24.00 km (14.91 mi)

M 4.3, Andreanof Islands, Aleutian Islands, Alaska
Tuesday, March 1, 2011 12:14:53 UTC
Tuesday, March 1, 2011 02:14:53 AM at epicenter
Depth: 130.40 km (81.03 mi)

M 2.8, Central California
Tuesday, March 1, 2011 12:07:16 UTC
Tuesday, March 1, 2011 04:07:16 AM at epicenter

Depth: 15.50 km (9.63 mi)

M 4.5, Kepulauan Babar, Indonesia
Tuesday, March 1, 2011 11:59:40 UTC
Tuesday, March 1, 2011 08:59:40 PM at epicenter
Depth: 144.80 km (89.97 mi)

M 3.3, Arkansas
Tuesday, March 1, 2011 10:56:20 UTC
Tuesday, March 1, 2011 04:56:20 AM at epicenter

Depth: 2.40 km (1.49 mi)

M 3.6, Kenai Peninsula, Alaska
Tuesday, March 1, 2011 10:36:42 UTC
Tuesday, March 1, 2011 01:36:42 AM at epicenter
Depth: 17.50 km (10.87 mi)

M 2.6, Arkansas
Tuesday, March 1, 2011 10:04:55 UTC
Tuesday, March 1, 2011 04:04:55 AM at epicenter
Depth: 2.40 km (1.49 mi)

M 4.0, South Island of New Zealand
Tuesday, March 1, 2011 09:42:06 UTC
Tuesday, March 1, 2011 10:42:06 PM at epicenter

Depth: 10.10 km (6.28 mi)

M 2.5, western Texas
Tuesday, March 1, 2011 06:31:59 UTC
Tuesday, March 1, 2011 12:31:59 AM at epicenter
Depth: 5.00 km (3.11 mi)

M 2.6, Puerto Rico region
Tuesday, March 1, 2011 05:12:56 UTC
Tuesday, March 1, 2011 01:12:56 AM at epicenter
Depth: 16.40 km (10.19 mi)

M 4.8, offshore Bio-Bio, Chile
Tuesday, March 1, 2011 04:08:43 UTC
Tuesday, March 1, 2011 01:08:43 AM at epicenter
Depth: 33.60 km (20.88 mi)

M 5.2, Ascension Island region
Tuesday, March 1, 2011 03:46:29 UTC
Tuesday, March 1, 2011 02:46:29 AM at epicenter
Depth: 10.30 km (6.40 mi)

M 2.7, Arkansas
Tuesday, March 1, 2011 03:35:29 UTC
Monday, February 28, 2011 09:35:29 PM at epicenter

Depth: 4.80 km (2.98 mi)

M 3.1, western Texas
Tuesday, March 1, 2011 03:30:12 UTC
Monday, February 28, 2011 09:30:12 PM at epicenter
Depth: 5.00 km (3.11 mi)

M 2.7, Northern California
Tuesday, March 1, 2011 02:29:21 UTC
Monday, February 28, 2011 06:29:21 PM at epicenter
Depth: 3.70 km (2.30 mi)

M 4.5, Northern California
Tuesday, March 1, 2011 02:19:46 UTC
Monday, February 28, 2011 06:19:46 PM at epicenter
Depth: 2.60 km (1.62 mi)

M 3.3, northern Alaska
Tuesday, March 1, 2011 01:07:09 UTC
Monday, February 28, 2011 04:07:09 PM at epicenter
Depth: 14.60 km (9.07 mi)

M 6.0, Easter Island region
Tuesday, March 1, 2011 00:53:46 UTC
Monday, February 28, 2011 05:53:46 PM at epicenter
Depth: 10.00 km (6.21 mi)

M 5.1, Easter Island region
Monday, February 28, 2011 23:42:17 UTC
Monday, February 28, 2011 04:42:17 PM at epicenter
Depth: 10.30 km (6.40 mi)

M 4.9, northern Sumatra, Indonesia
Monday, February 28, 2011 23:10:23 UTC
Tuesday, March 1, 2011 06:10:23 AM at epicenter
Depth: 33.90 km (21.06 mi)

M 5.2, Tarapaca, Chile
Monday, February 28, 2011 20:45:42 UTC
Monday, February 28, 2011 05:45:42 PM at epicenter
Depth: 99.00 km (61.52 mi)

M 2.6, Central Alaska
Monday, February 28, 2011 18:43:41 UTC
Monday, February 28, 2011 09:43:41 AM at epicenter
Depth: 5.60 km (3.48 mi)

M 4.7, Bonin Islands, Japan region
Monday, February 28, 2011 16:35:49 UTC
Tuesday, March 1, 2011 02:35:49 AM at epicenter
Depth: 489.00 km (303.85 mi)

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