The Good News: No Seismic Activity Linked to Injection Wells or Fracking in California

Several studies have been released recently that add to our understanding of the potential for oil and gas injection wells to cause earthquakes strong enough to be felt, a phenomenon known as “induced seismicity.” These studies have examined seismic activity in areas like Oklahoma, Texas, Ohio and Colorado that are less accustomed to earthquakes than we are in California. You can click the following links for more information from the United States Geological Survey (USGS), the University of Texas (UT) and Southern Methodist University (SMU), and the State of Oklahoma. Energy in Depth (EID) reviews and critiques of some of these reports can be found here and here.

Anti-industry activist groups try to stoke fears among Californians about these developments, but there is an important fact that has been obscured by the focus on seismic activity elsewhere in the country:

California, the nation’s most earthquake-prone state and the third largest energy producing state, has experienced no seismic activity attributed to injection wells or hydraulic fracturing. That’s right; of the approximately 42,000 Class II underground injection wells in California not one has been linked to seismic activity according to geophysicists and state regulators.

What accounts for this remarkable achievement? Industry best practices are no doubt one element, as producing in a fault-laden region means adopting best practices to ensure that seismicity does not become an issue.

There are other reasons for California’s sterling record in this area that have to do with the unique nature of production in the Golden State.

Seismologist Egill Hauksson of the California Institute of Technology provided insight into the reasons for this in a front-page Los Angeles Times story earlier this week, noting that development in California differs from elsewhere:

“One factor is that the Los Angeles Basin’s petroleum deposits are thick with oil. But in Oklahoma, workers need to break up dense shale rock to get the oil out of it, Hauksson said, which results in more toxic wastewater.

Another difference: In Southern California, wastewater is generally injected back into watertight traps where the oil came from. In Oklahoma, the wastewater is disposed of outside the oil fields and injected below the groundwater aquifer, where it can trickle down and trigger movement on a long-dormant fault, Hauksson said.

“If you start doing stuff like in Oklahoma … then, yeah, it’s a different ballgame,” Hauksson said. “But as long as they continue current operations, we don’t expect induced seismicity in L.A.”

Further explanations recently came from California State Geologist John Parrish and California-based USGS geophysicist William Ellsworth, who spoke with reporter Eric Hand of Science Magazine:

  “Why does California see so many fewer induced earthquakes than places like Oklahoma?

Parrish: Our geology is quite a bit different from the geology in the midcontinent and the eastern states. For one thing, their production formations are very old. California, we have very poorly consolidated sediments that are much younger.

Ellsworth: The change has been when water begins to be injected in virgin formations, places where no perturbations have happened before.    That seems to be to me at least one of the signatures for situations where can say these earthquakes have been induced.”

California’s oil and gas industry has been successfully and safely producing energy in our geologically challenging state for more than a century. It is perhaps no surprise that the scientists who work for the industry as well as the scientists that regulate it have extensive experience successfully mitigating any seismic risks, however small.

The California Department of Conservation recently promulgated emergency regulations to bring California’s Class II Underground Injection Control program into compliance with the federal Safe Drinking Water Act. This is an inter-agency regulatory correction; no seismic activity (or drinking water impact) has been alleged.

It should also be noted that not only have injection wells not caused felt seismic events in California, but neither has hydraulic fracturing (or “fracking”). State geologist Parrish, said in 2012 that “we have a lot of information about the seismicity that is caused by hydraulic fracking,” adding that “the magnitudes of these are all less than magnitude 1.” The Department of Conservation has confirmed that fracking has not led to felt seismic events and a 2012 study of the Inglewood Oil Field near Los Angeles, the largest urban oil field in the United States, found no incidence of felt seismic events as a result of hydraulic fracturing.

Stanford geophysicist and Obama Administration advisor Mark Zoback provided insight into the reason that fracking is extremely unlikely to case a felt earthquake. Speaking before the U.S. Senate, Zoback noted:

 “These microseismic events [from hydraulically fracturing a well] affect a very small volume of rock and release, on average, about the same amount of energy as a gallon of milk falling off a kitchen counter…Needless to say, these events pose no danger to the public.”


Induced seismicity linked to energy development is a very rare occurrence, even in places like Texas and Oklahoma. As the latest study from SMU and UT noted:

 “[T]ens of thousands of currently active injection wells apparently do not induce earthquakes or at least not earthquakes large enough to be felt or   recorded by seismic networks.”

EID released a study last month backing this up. We found that 99.9 percent of injection wells in the Barnett Shale region of North Texas have not been associated with felt seismicity.

The U.S. Environmental Protection Agency (EPA) has written that “very few” of injection wells have been linked to felt seismic events, and the agency has been complimentary of state disposal well programs.

While induced seismicity does not happen often, the increase in the number of earthquakes in other oil and gas-producing regions of the country is one that demands, and is receiving, diligent study. The industry has collaborated with scientists and regulators to adapt regulations where needed and to further understand the issue. The State Oil & Gas Regulatory Exchange, for example, recently created an induced seismicity working group, joining state regulatory agencies and geological surveys, along with the Ground Water Protection Council, to collaborate and share science and research and California’s energy producers will be an important part of this collaboration.


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