Petroleum production in the Permian Basin accelerated in 2007 and the first “anomalous” quake occurred in 2009, the study says. Since then, earthquakes have increased every year in the area.
In 2017, the most recent year the report covers, there were more than 2,000 seismic events, most of which were earthquakes, said Heather DeShon, a SMU associate professor and co-author on the paper.
“[The quakes] correspond in time and space with Delaware Basin Production,” DeShon said. “The earthquakes clearly began as production began.”
In the Delaware Basin, which is part of the Permian Basin in West Texas, technology advances allowed for increased oil and gas production starting in 2007.
Two years ago, Texas began using a statewide earthquake monitoring system, the Texas Seismic Monitoring Program. But before that, there was limited seismic information available. The purpose of the study was to figure out when the new set of earthquakes started and why, DeShon said.
"No one likes the idea that the earthquakes they are feeling are generated by people," she said.
Many human activities like quarry blasting and nuclear testing can generate seismic activity. Researchers wrote an algorithm to distinguish earthquakes from other seismic events and analyzed the results.
In their paper, which was accepted by the Journal of Geophysical Research, the 11-person team presented seismic data between 2000 and 2017. They also charted oil and gas production, wastewater disposal and hydraulic fracturing fluid use for the same years, and as those grew, so too did the number of seismic events.
The data the team used came from seismic monitoring stations about 150 miles south of Pecos, Texas. The monitors are very sensitive and the earth is quiet there so it was possible to get information about activity far away, according to the paper.
Although the data available didn't allow the team to pinpoint what part of oil and gas collection was responsible for the increase in earthquakes, the correlation was clear, DeShon said. Most of the seismic events isolated from the data occurred at or near the depth of oil and gas drilling.
But while the increase in human-induced earthquakes in the area is significant and growing, most of them are still not strong enough for people to feel. Human beings typically register earthquakes around a magnitude of 2.5 or 2.8 on the Richter scale. In earthquake-prone, highly populated areas, people learn what an earthquake vibration sounds like in a building and report feeling them at even lower registers, DeShon said.
"No one likes the idea that the earthquakes they are feeling are generated by people." — Heather DeShon
None of the events the team saw were higher than a magnitude 4, which is only strong enough to do minimal damage to a building located directly on top of the quake's epicenter. But that doesn't mean earthquakes won't get stronger over time, DeShon said.
What's important to understand now is the potential hazard of the earthquakes so that it is possible to mitigate their effects. Fault lines in West Texas are being reactivated and researchers now need to figure out how big these faults are and what their potential is for damage, she said.
“The information in this paper is a fundamental building block for the rest of the research being done,” DeShon said.
Researchers at SMU and other Texas universities are working to figure out the earthquakes, their causes and how to avoid serious damage from them. In Oklahoma, where earthquakes as high as a magnitude 5.8 have been recorded, oil and gas companies have taken steps to reduce the rate and size of earthquakes from oil and gas production, DeShon said.
“Well the hope is that we can mitigate induced earthquakes in Texas so no community experiences a damaging earthquake,” she said.