Nav: Home

Wastewater injection rates may have been key to Oklahoma's largest earthquake

May 02, 2017

Changes to the rate of wastewater injection in disposal wells may have contributed to conditions that led to last year's Pawnee earthquake in Oklahoma, according to a new report published May 3 as part of a focus section in Seismological Research Letters.

The magnitude 5.8 Pawnee quake, felt widely across Oklahoma, is the largest earthquake recorded in the state since the 1950s. Most Oklahoma earthquakes since 2009 are thought to have been triggered by wastewater produced by oil and gas drilling that has been injected back into the ground. The Pawnee earthquake occurred in a region with active wastewater disposal wells, and is potentially the largest such induced earthquake to have occurred in Oklahoma so far, write University of Oklahoma seismologists Xiaowei Chen and Norimitsu Nakata in their preface to the section.

When Andrew Barbour of the U.S. Geological Survey and colleagues examined new injection data from nearby disposal wells in Osage County, they found a significant increase in injection rates in the years leading up to the Pawnee mainshock. Some wells injected wastewater at a constant rate, while others injected the water at a variable rate. The overall injected volume was roughly the same between these two types of wells.

Barbour and colleagues' models of injection indicate, however, that it may have been the variable-rate wells that were most important for the Pawnee event. Their findings suggest that "long-term injection may have been responsible for a gradual loading of the fault to the point where it primed the fault for failure triggered by the short-term high-rate injection..." the authors write. They note that in the absence of these variable rate injections, however, the fault may have still failed at a much later time.

Other papers in the Pawnee special focus section include:
  • Raphaël Grandin and colleagues at the Institut de Physique du Globe de Paris used satellite radar data (InSAR) to determine that the main Pawnee seismic rupture occurred between 4 and 9 kilometers depth, well below the main sediment layer where wastewater is injected. Since the fault that was activated in the Pawnee event was unknown before, the researchers say the future risk of a magnitude 6 event triggered by fluid injection "remains an open question."

  • Combining InSAR, GPS and other data, Fred Pollitz of the U.S. Geological Survey and colleagues, and Eric Fielding of Jet Propulsion Laboratory and colleagues developed models of fault slip and took a closer look at surface changes from the Pawnee quake. Fielding and colleagues confirmed that there was no significant evidence of a surface rupture from the quake, while Pollitz and colleagues found signs of fault zone collapse around an area of high slip on the fault. They suggest the collapse might represent compaction of cracks in the rock that developed during the fault rupture, as fluids migrated away from the fault zone.

  • Kayla Kroll of Lawrence Livermore National Laboratory and colleagues report their observations of water level changes in two monitoring wells in response to the Pawnee quake and to the November 2016 magnitude 5.0 Cushing earthquake. Fluid levels rose with the Pawnee quake and lowered slightly with the Cushing quake, indicating that the Pawnee earthquake especially altered the fluid flow through regional rock layers up to 50 kilometers from the Pawnee mainshock. In another paper by Chi-Yuen Wang of UC Berkeley and colleagues, the researchers note that enhanced permeability of regional rock may be behind changes to groundwater levels up to 150 kilometers from the Pawnee epicenter.

  • Unlike previous Oklahoma earthquakes, the Pawnee quake produced a variety of ground surface liquefaction features, such as fractures, sand blows and ground spreading and subsidence. Folarin Kolawole of Oklahoma State University and colleagues took a closer look at those features with a "CAT scan"-style technology called high resolution electrical resistivity tomography (ERT).

  • An analysis of foreshock activity by Jacob Walter of the Oklahoma Geological Survey and colleagues demonstrates a gradual fault stress increase in the months prior to the Pawnee mainshock. Colin Pennington and Xiaowei Chen of the University of Oklahoma investigated stress interactions between the main faults in the area, concluding that the three Pawnee foreshocks promoted the failure of the fault for the Pawnee mainshock and early aftershock, and that the mainshock led to the fault failure behind further aftershocks.

  • Stress parameters for the Pawnee and two other Oklahoma earthquakes are similar to those estimated for other potentially induced earthquakes in the central and southern U.S., and to shallow natural earthquakes, according to a paper by Chris Cramer of the University of Memphis. Stress parameters measure the difference in stress across a fault before and after an earthquake.

Seismological Society of America

Related Stress Articles:

Captive meerkats at risk of stress
Small groups of meerkats -- such as those commonly seen in zoos and safari parks -- are at greater risk of chronic stress, new research suggests.
Stress may protect -- at least in bacteria
Antibiotics harm bacteria and stress them. Trimethoprim, an antibiotic, inhibits the growth of the bacterium Escherichia coli and induces a stress response.
Some veggies each day keeps the stress blues away
Eating three to four servings of vegetables daily is associated with a lower incidence of psychological stress, new research by University of Sydney scholars reveals.
Prebiotics may help to cope with stress
Probiotics are well known to benefit digestive health, but prebiotics are less well understood.
Building stress-resistant memories
Though it's widely assumed that stress zaps a person's ability to recall memory, it doesn't have that effect when memory is tested immediately after a taxing event, and when subjects have engaged in a highly effective learning technique, a new study reports.
Stress during pregnancy
The environment the unborn child is exposed to inside the womb can have a major effect on her or his development and future health.
New insights into how the brain adapts to stress
New research led by the University of Bristol has found that genes in the brain that play a crucial role in behavioural adaptation to stressful challenges are controlled by epigenetic mechanisms.
Uncertainty can cause more stress than inevitable pain
Knowing that there is a small chance of getting a painful electric shock can lead to significantly more stress than knowing that you will definitely be shocked.
Stress could help activate brown fat
Mild stress stimulates the activity and heat production by brown fat associated with raised cortisol, according to a study published today in Experimental Physiology.
Experiencing major stress makes some older adults better able to handle daily stress
Dealing with a major stressful event appears to make some older adults better able to cope with the ups and downs of day-to-day stress.

Related Stress Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#529 Do You Really Want to Find Out Who's Your Daddy?
At least some of you by now have probably spit into a tube and mailed it off to find out who your closest relatives are, where you might be from, and what terrible diseases might await you. But what exactly did you find out? And what did you give away? In this live panel at Awesome Con we bring in science writer Tina Saey to talk about all her DNA testing, and bioethicist Debra Mathews, to determine whether Tina should have done it at all. Related links: What FamilyTreeDNA sharing genetic data with police means for you Crime solvers embraced...