Distant Quakes Trigger Tremors at U.S. Waste-Injection Sites
This post excerpts the releases for two new important articles in the journal Science. The first is “Enhanced Remote Earthquake Triggering at Fluid-Injection Sites in the Midwestern United States” (subs. req’d). The second is a review article, “Injection-Induced Earthquakes” (subs. req’d) by U.S. Geological Survey geophysicist William Ellsworth. The first release, from Columbia University’s Lamont-Doherty Earth Observatory, explains:
A surge in U.S. energy production in the last decade or so has sparked what appears to be a rise in small to mid-sized earthquakes in the United States. Large amounts of water are used both to crack open rocks to release natural gas through hydrofracking, and to coax oil and gas from underground wells using conventional techniques. After the gas and oil have been extracted, the brine and chemical-laced water must be disposed of, and is often pumped back underground elsewhere, sometimes causing earthquakes.
Earthquakes induced by fracking wastewater reinjection are a major concern because those wells are already prone to fail and leak (see “Natural Gas, Once A Bridge, Now A Gangplank“). The Propublica exposé in Scientific American, “Are Fracking Wastewater Wells Poisoning the Ground beneath Our Feet?” quoted engineer Mario Salazar, who worked for a quarter century as a technical expert with the EPA’s underground injection program: “In 10 to 100 years we are going to find out that most of our groundwater is polluted. A lot of people are going to get sick, and a lot of people may die.”
Here is an extended excerpt from the Columbia release:
Large earthquakes from distant parts of the globe are setting off tremors around waste-fluid injection wells in the central United States, says a new study. Furthermore, such triggering of minor quakes by distant events could be precursors to larger events at sites where pressure from waste injection has pushed faults close to failure, say researchers.
Among the sites covered: a set of injection wells near Prague, Okla., where the study says a huge earthquake in Chile on Feb. 27, 2010 triggered a mid-size quake less than a day later, followed by months of smaller tremors. This culminated in probably the largest quake yet associated with waste injection, a magnitude 5.7 event which shook Prague on Nov. 6, 2011. Earthquakes off Japan in 2011, and Sumatra in 2012, similarly set off mid-size tremors around injection wells in western Texas and southern Colorado, says the study….
“The fluids are driving the faults to their tipping point,” said lead author Nicholas van der Elst, a postdoctoral researcher at Columba University’s Lamont-Doherty Earth Observatory. “The remote triggering by big earthquakes is an indication the area is critically stressed.”
… “We’ve known for at least 20 years that shaking from large, distant earthquakes can trigger seismicity in places with naturally high fluid pressure, like hydrothermal fields,” said study coauthor Geoffrey Abers, a seismologist at Lamont-Doherty. “We’re now seeing earthquakes in places where humans are raising pore pressure.”
The new study may be the first to find evidence of triggered earthquakes on faults critically stressed by waste injection. If it can be replicated and extended to other sites at risk of manmade earthquakes it could “help us understand where the stresses are,” said William Ellsworth, an expert on human-induced earthquakes with the USGS who was not involved in the study.