By EMILY SCHMALL and KRISTI EATON
2014-06-27 03:22 AM
OKLAHOMA CITY (AP) -- Residents of a U.S. state whose homes and nerves have been shaken by an upsurge in earthquakes want to know what's causing the temblors with hundreds expected to turn out for a meeting Thursday on the issue.
Oklahoma recorded nearly 150 earthquakes between January and the start of May, 145 quakes of 3.0 magnitude or greater, according to the Oklahoma Geological Survey. That compares with an average of two such quakes from 1978 to 2008. Recently, nighttime shaking has been strong enough to wake residents.
Earthquakes used to be almost unheard of in Oklahoma, but they've become common in recent years.
Many residents suspect hydraulic fracturing -- which involves blasting water, sand and chemicals deep into underground rock formations to free oil and gas -- may be to blame.
Seismologists already know that hydraulic fracturing can cause microquakes that are rarely strong enough to register on monitoring equipment.
However, fracking also generates vast amounts of wastewater, far more than traditional drilling methods. The water is pumped it into so-called injection wells, which send the waste thousands of feet underground. No one knows for certain exactly what happens to the liquids after that. Scientists wonder whether they could trigger quakes by increasing underground pressures and lubricating faults.
Still, seismologists -- and the oil and gas industry -- have taken pains to point out that a clear correlation has not yet been established.
After years of demands by anxious residents, governments in Oklahoma, Texas and Kansas, which have also seen an upswing in earthquakes, are confronting the issue, reviewing scientific data, holding public discussions and considering new regulations.
"This is all about managing risks," said Oklahoma Corporation Commission spokesman Matt Skinner. "It's a little more complicated than that because, of course, we're managing perceived risks. There's been no definitive answers, but we're not waiting for one. We have to go with what the data suggests."
Regulators from the Oklahoma, Texas and Kansas met for the first time in March in Oklahoma City, Oklahoma, to exchange information on the quakes and discuss toughening standards on the lightly regulated business of fracking wastewater disposal.
Residents in Texas, who have endured hundreds of small quakes, went to the state Capitol earlier this year to demand action by the state's chief oil and gas regulator. The commission hired the first state seismologist, and lawmakers formed the House Subcommittee on Seismic Activity.
After Kansas recorded 56 earthquakes between last October and April, the governor appointed a three-member task force to address the issue.
Nationwide, the United States has more than 150,000 injection wells, according to the Society of Petroleum Engineers, and only a handful have been proven to induce quakes.
"The link between injection wells and earthquakes is something we are still in the process of studying," said Heather DeShon, associate professor of geophysics at SMU.
Emily Schmall and Tim Talley contributed to this report.
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