If seismic activity in California and the bustling oil industry there are in any way linked — and a recent study led by researchers at CalTech adds to evidence that they might be — then state regulators may only have themselves to blame. That’s the implication of a recent analysis by the Center for Biological Diversity, an environmental advocacy group, which found that between April of 2015 and March of 2016, the California Division of Oil, Gas and Geothermal Resources issued dozens of permits to oil companies for wastewater disposal wells near active seismic faults.
Wastewater disposal is an issue that has long affected the oil and gas industries, though critics like to point the finger at the more recent rise of hydraulic fracturing, or fracking. During the fracking process, oil and gas companies send a high-pressure cocktail of water, sand and chemicals deep underground to force open fissures in rock formations and allow hydrocarbons to flow to the surface. That liquid cocktail — along with a mixture of water, heavy metals, salts and other contaminants picked up from thousands of feet underground — also flows back to the surface, leaving energy companies with a significant wastewater disposal problem on their hands.
According to one recent analysis, some 210 billion gallons of fracking wastewater were generated between 2005 and 2014 in the U.S. alone.
Of course, that’s in addition to the many billions of gallons of salty wastewater produced from all sorts of oil and gas production activity each year. Some of that wastewater is recycled, but a great deal of it is injected back underground for (presumably) safe and permanent storage. In all, the Environmental Protection Agency estimates that roughly 2 billion gallons of oil and gas industry wastewater is injected underground in the U.S. every single day — more than 700 billion gallons each year.
The vast majority of this activity proceeds without incident, but the potential for some injections to trigger earthquakes is nonetheless well known. “The injection of wastewater and salt water into the subsurface can cause earthquakes that are large enough to be felt and may cause damage,” the U.S. Geological Survey has noted. The agency has also suggested that seismic activity from such wells “can be induced at distances of 10 miles or more away from the injection point, and at significantly greater depths than the injection point.”
A Congressional Research Service report from last year also noted that, since 2009, the number of earthquakes exceeding a magnitude 3.0 has increased dramatically in the Eastern and Central parts of the country — “from an average of approximately 20 per year between 1970 and 2000 to over 100 per year in the period 2010-2013.”
At least some of this increased seismicity, the reported noted, appears linked to wastewater disposal wells.
California regulators, however, remain unconvinced that this is an issue for the Golden State, and they have issued wastewater well permits that critics say are troublingly close to active fault lines. Over the last year, at least 23 permits for new wastewater wells, along with 29 permits to rework old wells, were located within just eight miles of an active fault — and in some cases much, much closer — according to the Center for Biological Diversity’s analysis.
“We looked at the permits that regulators had been approving for new wastewater injection wells, and we found out that they are approving many that are very close to active faults — some of them are just yards away,” said Patrick Sullivan, the climate media director at the CBD.
The state issued permits for two new wells in Kern Country, for example, that were less than a quarter-mile away from an active fault, according to data from the CBD. A rework permit was granted for a well in Los Angeles County that was just two meters from a fault.
“State regulators,” Sullivan said, “just don’t seem to be addressing this issue.”
But Donald Drysdale, a spokesman for the California Department of Conservation which oversees the Division of Oil, Gas and Geothermal Resources, dismissed the concern in an email message. “Although there currently is no definitive answer to the question of whether there’s a correlation between wastewater injection and earthquakes in California,” Drysdale said, “the California Geological Survey and Division of Oil, Gas and Geothermal Resources concur that the likelihood is low.”
Compared to other parts of the country, Drysdale suggested the younger rocks of California require less pressure to inject wastewater, meaning less stress on faults. Earthquakes in the state also tend to happen four or five miles deeper than where companies frack or inject wastewater, Drysdale said, adding that the EPA must approve each well, and that the public is able to provide input before any permit issued.
“[T]here’s a very transparent, thorough process in place,” he said.
California also has “the most extensive seismic monitoring network in the nation,” Drysdale suggested, so if there was a connection between energy company practices and seismic activity, the state’s geologists would know about it.
Sullivan disputed that assertion. Given the high frequency of seismic activity in California, he suggested, some earthquake patterns might well get lost amid the noise. This is different from areas like Oklahoma, he noted, where a sudden increase in earthquakes immediately stands out.
Sullivan also suggested that while numerous studies have been conducted in the Eastern and Central parts of the country, the potential link between injection wells and seismicity in California is under-studied, making the recent analysis by CalTech resaerchers, published earlier this year in the journal Geophysical Research Letters, all the more important.
That study, which looked at earthquakes along the White Wolf Fault in southern California, is the first to draw direct links between injection wells and seismic activity in the state. “Hydrogeological modeling revealed that wastewater disposal likely contributed to seismicity via localized pressure increase along a seismically active fault,” the researchers noted. “Our results suggest that induced seismicity may remain undetected in California without detailed analysis of local geologic setting, seismicity, and fluid diffusion.”
To be sure, earthquakes induced by injection well activity are typically small — less than magnitude 5.0 — although stronger ones have been detected. In 2011, for example, a magnitude 5.6 earthquake – the largest human-induced earthquake ever recorded – destroyed 14 homes and injured two people in Oklahoma. And David Jackson, a professor emeritus of geophysics at the University of California, Los Angeles, says that even small earthquakes can put stress on active faults, which can lead to larger and more powerful quakes.
“A lot of people think that small earthquakes reduce stress,” Jackson said. “That is clearly wrong.”
While small quakes can reduce stress on a single fault, they put more stress on connected or nearby faults, Jackson said. Small earthquakes can also cause aftershocks that are larger than the original. That doesn’t happen often, Jackson said, but an increase in the number of quakes will increase the chances of a big earthquake. He also points out that many small earthquakes can have an effect that is comparable to a single, much bigger earthquake.
“It’s like, what are more dangerous, bears or bees?” Jackson said. “Normally a single bee won’t kill you or chase you up a tree, but a bunch of them [might].”