Risk of quakes on the rise in Oklahoma, North Texas

Bricks fell from this home in Sparks, Okla., after three quakes hit the area in less than 24 hours on Nov. 6, 2011.
Bricks fell from this home in Sparks, Okla., after three quakes hit the area in less than 24 hours on Nov. 6, 2011. Associated Press archives

The ground east of the Rockies is far more likely to shake this year with damaging though not deadly earthquakes, federal seismologists report in a new risk map for 2016.

Much of that risk is a man-made byproduct of drilling for energy, experts say.

The new risk assessment, which for the first time identifies potential ground-shaking hazards from induced and natural earthquakes, shows that residents in North Texas are as likely to feel the earth move in 2016 as people living in some parts of California, said a geophysicist with the U.S. Geological Survey.

“It is much higher because the earthquake rates have been higher than normal over the last six years,” said Rob Williams, the agency’s coordinator for the earthquake program for the central and eastern United States.

Parts of Oklahoma also now match northern California for the nation’s most shake-prone, according to the report, with one north-central Oklahoma region having a 1 in 8 chance of dealing with a damaging quake in 2016, with other parts closer to 1 in 20.

There’s no question that there’s a lot of shaking going on in Oklahoma, Kansas and Texas.

Mark Petersen, National Seismic Hazard Mapping Project

Overall, 7 million people live in areas where the risk has dramatically jumped for earthquakes, with the report suggesting disposal of wastewater, a byproduct of oil and gas drilling, as the cause. That activity is concentrated in Oklahoma, Texas, New Mexico, Kansas, Colorado and Arkansas.

Natural earthquake risk also increased around the New Madrid fault in Missouri, Tennessee, Kentucky, Arkansas and Illinois.

Past efforts by the U.S. Geological Survey looked at 50-year risks and didn’t include man-made quakes. The new risks are mostly based on increases in quakes felt last year.

These are not massive quakes killing hundreds of people and leaving devastation in their wake, said Williams and Mark Petersen, chief of the National Seismic Hazard Mapping Project. They damage, but don’t topple, buildings.

In the Dallas-Fort Worth area, for example, there were nine earthquakes that measured 3 or more on the Richter scale from November 2014 through 2015, Williams said. The biggest in the Irving-Dallas area was a 3.6 earthquake that occurred on Jan. 6, 2015, he said.

“We have anecdotal data of people experiencing the earthquakes, cracks and things falling off shelves,” Williams said.

Petersen said “these are much higher ground motions” than the last time he created the long-term map in 2014. “There’s no question that there’s a lot of shaking going on in Oklahoma, Kansas and Texas,” Petersen said in an interview after a news conference.

For example, on the 2014 map the risk was low in Dallas; now, after a tenfold increase in risk, Petersen said, the Dallas-Fort Worth area risk is between 2 to 5 percent this year.

“Oklahoma and Texas have the largest population exposed to induced quakes,” Petersen said. The largest earthquake in North Texas was a 4.0 earthquake last May with an epicenter near Venus.

Williams said they are not trying to “scare people.” He said people are not leaving California, for example, because of the frequency of earthquakes.

“But this is what having a whole lot of earthquakes will do. The more small earthquakes you have, the more of a chance [there is] of having a bigger one,” Williams said.

North Central Oklahoma was said to have a 12 percent risk, and it has already been hit: A 5.1 magnitude quake caused some damage around Fairview in February.

Seismologist Rowena Lohman of Cornell University, who wasn’t part of the map team, said the increase around Oklahoma is easily noticeable and scientists are trying to determine whether these man-made smaller quakes lead to larger events.

Induced quakes are to blame for much of the problem. They result when wastewater is injected deep underground, said USGS seismologist Justin Rubinstein, the deputy chief of the mapping program. That injection is a byproduct of energy drilling, including hydraulic fracturing used to drill for oil and gas. But he said the fracking process itself mostly doesn’t cause quakes strong enough to be damaging, while injecting fracking waste does.

Rubinstein said there is a scientific consensus “that wastewater disposal does cause earthquakes.”

A study by Southern Methodist University scientists linked the oil and gas process to the flurry of earthquakes that hit the Azle and Reno area in 2013 and 2014.

Earlier this month, fears that wastewater injection wells may be linked to seismicity led the U.S. Army Corps of Engineers to limit them within 5 miles of a dam at Joe Pool Lake. The nearest injection well to the dam is now 9 miles away.

Arkansas, Kansas and Ohio saw dramatic reductions in man-made quakes when those states tightened restrictions on wastewater injections, Rubinstein said.

In Oklahoma, “the longer we go, the more we pump down there, the more likelihood we have that we’re going to have larger quakes,” Petersen said.

Oklahoma Gov. Mary Fallin said the research justifies action taken by Oklahoma this year to cut back on injections.

“Recent declines in produced wastewater disposal in Oklahoma are not reflected in the USGS map,” Fallin said. “This gives us even a stronger base in going forward and gives state regulators further justification for what they are doing.”

Rubinstein said it’s too early to see any results from Oklahoma’s new efforts.

The increase in the natural quakes in the New Madrid area remains a mystery, Petersen said, but “it’s higher than it’s been in several years.”

Staff writer Max B. Baker contributed to this report.

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