STUDY: Oil Industry Triggers California Earthquakes

The oil industry must now admit that its actions could cause earthquakes in California. A study published by the American Geophysical Union this week found that a swarm of earthquakes that occurred in Kern County in 2005 was almost certainly caused by underground injection of wastewater from the state's oil industry.

Earthquakes have long been linked to the injection of oil industry wastewater underground in other parts of the country--from Oklahoma to Ohio--but this is the first study to establish the connection in the Golden State where so many people already worry about the Big One.

The 2005 earthquake swarm occurred along the White Wolf fault at the southern end of Kern County. The peak of the earthquake activity documented in this study happened on Sept. 22, 2005, when there were three quakes, the biggest registering magnitude 4.6. The scientists calculated the odds of that happening naturally at just 3 percent.

Kern is the largest oil producing county in California. And it recently passed an ordinance that would greenlight decades of oil drilling, fracking, and underground wastewater injection without further environmental review. We're challenging that ordinance in court because it allows activities we know threaten our water, air, wildlife, and health. Today's study adds earthquakes to that list, providing further evidence that underground injection is dangerous and requires location-specific consideration.

Kern County, like most of California, is crisscrossed with fault lines. Most of California's faults have never been mapped. Between 2001 and 2010, the rate of wastewater injection in this part of Kern increased, rising up to 100,000 cubic meters/month--that's over 26.4 million gallons of water each month or 316.8 million gallons a year being injected underground. That amount is equivalent to the annual water use of 2,171 four-person family homes. Or, it's enough water to fill 480 Olympic swimming pools. All that water put pressure on the White Wolf fault.

What's scary is that induced earthquakes of this kind don't necessarily happen right away or at the location of the well. As the study's authors (T.H.W. Goebel et al.) explain, fluid injection "can change the local stress field potentially causing earthquakes at several kilometers distance, both immediately and months to years after peak injection."

We've known for some time that underground injection risks contaminating our water. As NRDC Senior Scientist Briana Mordick has blogged about, California has improperly permitted thousands of injection wells to pump wastewater and other fluids into federally protected drinking water aquifers. Indeed, the Tejon Oil Field, where this study took place, contains four improperly permitted wells. One of those four is featured in this paper, and the operator of that injection well is seeking an exemption so it can keep pumping into the aquifer.

Now we know that injecting oil and gas wastewater underground risks earthquakes here too. The United States Geological Survey reports that the average rate of earthquakes in the central and eastern United States has increased from a long-time average of 21 per year to over 100 a year since 2010, with 188 in 2011. That increase is almost certainly linked to a rise in oil and gas activity.

We can't allow Kern County to give a free pass to industry actions that we now know with near certainty can cause earthquakes in California.

About the Authors

Giulia C.S. Good Stefani

Attorney, Marine Mammal and Southern California Ecosystems projects

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