AZLE, Texas — Earthquakes used to be almost unheard of on the stretches of prairie that span Texas, Kansas and Oklahoma.
But in recent years, temblors have become commonplace. Oklahoma recorded nearly 150 of them between January and the start of May. Most were too weak to cause serious damage or endanger lives. Yet they've rattled nerves and raised suspicions that the shaking might be connected to the oil and gas drilling method known as hydraulic fracturing, especially the wells in which the industry disposes of its wastewater.
Governments in all three states are finally confronting the issue, reviewing scientific data, holding public discussions and considering new regulations.
Today in Edmond, Okla., hundreds of people are expected to turn out for a meeting that will include the state agency that regulates oil and gas drilling and the Oklahoma Geological Survey.
States with historically few earthquakes are trying to reconcile the scientific data with the interests of their residents and the oil and gas industry.
Regulators from each state met for the first time in March to exchange data on quakes and discuss toughening standards on the lightly regulated business of fracking wastewater disposal.
In Texas, residents from Azle, a town northwest of Fort Worth that has had hundreds of small quakes, demanded action by the state's chief oil and gas regulator, the Railroad Commission. The commission hired the first-ever state seismologist, and lawmakers formed the House Subcommittee on Seismic Activity.
After Kansas recorded 56 earthquakes between October and April, the governor appointed a three-member task force.
Seismologists know that hydraulic fracturing — which involves blasting water, sand and chemicals deep underground to free oil and gas — can cause microquakes that are rarely strong enough to register on monitoring equipment.
However, fracking also generates vast amounts of wastewater. The water is pumped 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.