Series of quakes shake Searcy area
A United State Geological Survey map shows a series of small earthquakes felt in the Searcy area in recent days.
LITTLE ROCK — Geologists are installing a temporary sensor just west of Searcy to record seismic activity after a series of earthquakes that have rattled the area in recent days.
The U.S. Geological Survey lists nine quakes in White County since Saturday, with the strongest occurring that night about 7 miles northwest of Garner. That quake measured 3.3 on the Richter scale.
The quakes have continued each day since, including a 2.2-magnitude earthquake reported just before 10:30 a.m. Tuesday about 6 miles west of Searcy. More than 100 people have reported feeling the stronger tremors.
Scott Ausbrooks, the geohazards supervisor with the Arkansas Geological Survey, said the temporary earthquake sensor should be online by the end of this week and will record better data should more quakes occur in the same White County region.
"You can equate it to tornado-chasing," Ausbrooks said by phone from the White County site. "You hate to say it but you need more earthquakes to get more data."
The state geological survey already has six earthquake sensors set up in parks around Arkansas, but officials deploy the temporary one to hone in on particularly active areas. The result, should more quakes occur, will be more detailed information about the depth of the quake.
That's important, Ausbrooks said, because it sheds light on what's causing the shaking.
If the quakes are occurring deep in the ground, it would likely eliminate natural gas drilling as a possible contributor.
White County is one of 10 counties within the Fayetteville Shale, where there are more than 2,000 wells drilling for natural gas. But Ausbrooks said such efforts usually extend no further than 8,000 feet into the ground.
"If the earthquakes are occurring much deeper, then it's a lot harder to make that connection," he said. "If the depths they're actually drilling is where the activity is, it's not a definitive answer at that point. But at least it gives you an idea."
No causal evidence linking the drilling and the quakes yet exists, Ausbrooks stressed. And the area has not previously been immune from seismic activity, he said, so the latest quakes may be entirely natural.
Over the span of a year starting in 1982, more than 20,000 earthquakes were reported in the area surrounding the Faulkner County town of Enola, including 93 quakes that were felt and three that registered greater than a magnitude 4, Ausbrooks said.
Don Blakeman, a geophysicist with the U.S. Geological Survey, said quakes like the ones reported recently in White County can continue for weeks, often with no "main shock" or more powerful earthquake standing out from the bunch.
He said scientists have found certain earthquakes to have been caused by man-made operations, such as re-injecting fluids in an oil field or emptying a large reservoir. But definitively saying whether a quake was caused by such work is always tough.
"A lot of people think 'oh we're hiding something,'" Blakeman said. "We're not. It's up in the air because it's very hard to figure out correlation. It's not like you drill a well and the next day you get a whole bunch of earthquakes. And in areas like Arkansas that have earthquakes anyway, it's hard to know what's natural and what's not."
This article was published June 29, 2010 at 3:36 p.m.Source
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