UT research says most Texas earthquakes caused by human activity

Earthquakes...we've seen them on TV in other parts of the country and the world.
But here in the Lone Star State, when an earthquake happens, you may not even feel it.

UT Senior Research Scientist Cliff Frohlich and his colleagues compiled a "review paper" -- connecting dots between past Texas earthquakes...and oil and gas production.

"As the oil business has changed, the earthquakes have changed but they've been there for 90 years," Frohlich said.

Frohlich says even though hydraulic fracturing has been the primary cause of the man-made earthquakes over the past decade, non-natural Texas quakes have been happening for much longer than that.

"The first quake we found that was probably caused by human activity was in 1925 and there have been earthquakes in the '30s and the '50s and so-on.  So it's not a new phenomena in Texas," Frohlich said.

According to the study, 59% of Texas earthquakes since 1975 are considered "almost certainly" or "probably" triggered by oil and gas production.  Another 28%  --  "possibly" due to oil and gas.  13% were natural.
Frohlich, who doesn't believe fracking is harmful to the environment, also doesn't believe the usually small Texas earthquakes are a bad thing either.
He says a magnitude 3.5 earthquake is kind of like a thunderstorm.

"The next day people say 'did you hear it?'  And maybe a tree branch falls and it's exciting.  If you have a hurricane with 200 mile an hour winds it's not exciting it's a disaster," Frohlich said.

And Frohlich doesn't believe oil and gas production will lead to a catastrophic earthquake in Texas like the recent magnitude 9 in Japan.  He says the biggest earthquakes in Texas have been around magnitude 6.

"If these kinds of things cause huge earthquakes, Texas would be famous for huge earthquakes that rock the state all the time," Frohlich said.

The Texas Railroad Commission regulates the oil and gas industry in the state.  In response to this study a spokesperson says they have a staff seismologist and they take seismicity very seriously.

Saying in part: "The commission will continue to use objective, credible scientific study as the basis for our regulatory and rulemaking functions.  However this new study acknowledges the basis for its conclusions are purely subjective in nature and in fact, admits its categorization of seismic events to be arbitrary."

Frohlich isn't bothered by push back.  He says science is a dialogue.

"I'm not opposed to people -- scientists or railroad commissioners who want to question our study...that's progress.  That's how we arrive at a decision.  And ultimately we'll know more," Frohlich said.

Frohlich makes the point that it really depends on where an earthquake is.  He says a magnitude 5 in Dallas would be a billion dollar problem.

But a magnitude 6.5 in parts of West ,Texas wouldn't be a big deal.
Frohlich's paper is published today in the journal seismological research letters.

Here's the Railroad Commission's full statement:

"The Railroad Commission takes the issue of seismicity very seriously and has taken several actions to address this issue. The Commission has hired a staff seismologist (started April 1, 2014); held show-cause hearings requiring certain disposal well operators to provide evidence their operations are not inducing seismicity in North Texas; hosted a technical hearing on seismicity and oil and gas activity; and implemented some of the most stringent rules in the nation on seismicity.

These rules include requiring applicants for new disposal wells to conduct a survey of the U.S. Geological Survey seismic database for historical earthquakes within a circular area of 100 square miles around a proposed, new disposal well. If historic seismic data is found, the survey must be submitted to the Commission and may impact the approval, denial or amendment of the operator's application. The rules also clarify Commission's staff authority to modify, suspend or terminate a disposal well permit, including modifying disposal volumes and pressures or shutting in a well if scientific data indicates a disposal well is likely to be, or determined to be contributing to seismic activity. And our seismic rules allow Commission staff to require operators to disclose reported injection volumes and pressures on a more frequent basis.

Since these seismicity disposal well rules went into effect Nov. 17, 2014 through May 11, 2016, the Railroad Commission has received 51 disposal well applications in areas of historic seismicity. Of these, 22 permits have been issued with special conditions, such as requirements to reduce maximum daily injection volumes and pressure and/or to record volumes and pressures daily as opposed to monthly. Ten applications were returned or withdrawn. Four applications were protested and sent to hearing. Nine permits were issued without special conditions, and six applications are pending.

Following a 4.0 magnitude earthquake in the Mansfield area last year, the Commission immediately ordered testing of five disposal wells in the vicinity of the estimated epicenter.  The tests, which required the wells to temporarily cease operation, showed no evidence of a bounding fault. After reviewing completion records for the disposal wells, the Commission required one well to be plugged back to a shallower depth.

Also, last summer Railroad Commissioner Ryan Sitton convened a technical hearing of seismicity experts, energy industry experts and Commission staff to discuss the issue of seismicity.

Additionally, the Railroad Commission is looking forward to the full implementation of the TexNet system to help gain a better understanding of natural and induced seismicity in Texas. The Commission's seismologist will be working closely with the TexNet team on this important program.

The Commission will continue to use objective, credible scientific study as the basis for our regulatory and rulemaking functions. However this new study acknowledges the basis for its conclusions are purely subjective in nature and in fact, admits its categorization of seismic events to be arbitrary."