Nav: Home

Damaging Sichuan earthquakes linked to fracking operations

April 04, 2019

Two moderate-sized earthquakes that struck the southern Sichuan Province of China last December and January were probably caused by nearby fracking operations, according to a new study published in Seismological Research Letters.

The December 2018 magnitude 5.7 and the January 2019 magnitude 5.3 earthquakes in the South Sichuan Basin caused extensive damage to farmhouses and other structures in the area. The December earthquake was especially destructive, injuring 17 people and resulting in a direct economic loss of about 50 million Chinese Yuan Renminbi (roughly $US 7.5 million).

The Changning shale gas block in the South Sichuan Basin has been the site of fracking operations since 2010, with extensive horizontal fracking injection wells becoming more common since 2014. The earthquake rate in the Changning block rose dramatically at the same time that systematic fracking began.

In the United States, wastewater disposal from oil and gas operations, where water produced during hydrocarbon extraction is injected back into rock layers, is thought to be the primary cause of induced earthquakes, especially in Oklahoma. However, there is growing evidence that hydraulic fracturing, or fracking, which uses injected water to break apart rock layers during hydrocarbon extraction, may have caused moderate-size earthquakes at some sites in Ohio, Oklahoma and western Canada.

Both wastewater disposal and fracking have induced earthquakes in the south Sichuan basin, say Xinglin Lei of the Geological Survey of Japan and colleagues. In their new study in SRL, the researchers present "a full chain of evidence" to show that the December and January earthquakes were induced by fracking operations.

They pinpointed the location of the earthquakes, finding that they were relatively shallow (between two and ten kilometers below the surface), as would be expected for induced earthquakes. The December and January quakes also coincided in time and space with injection at nearby fracking well pads. They did not have the exact injection volumes at these well pads to better understand the relationship between injection activities and the evolution of seismicity.

Lei and colleagues' modeling of seismic activity show that most of the activity came from the initial mainshocks, with little aftershock activity, which is also consistent with the pattern seen for induced earthquakes. Finally, their calculations show that overpressure on the rock pores, produced by the fracking injections, was strong enough to activate preexisting faults in the region. These faults were mostly unmapped and not in a favorable orientation to slip under normal tectonic activity, the researchers note.

"For most well pads, the associated seismicity fades out quickly after the hydraulic fracture ended or halted," said Lei, although he noted that their analysis did raise the possibility of seeing signs of fault reactivation from previous seismicity.

"In my opinion, repeated moderate earthquakes can be caused as long as the injection is continuing, since a moderate earthquake releases very limited strain," he added. "The national regulations in China should be updated with the requirement for operators to take action if some signs of fault reactivation were observed."

The researchers say more information is needed about faults and their stress patterns in areas of the Sichuan basin surrounding fracking well pads, to guide drilling in a way that would avoid moderate seismic activity. "Moderate earthquakes were observed in a limited number of sites," said Lei. "If these sites could be screened out, the risk of moderate earthquakes would be greatly reduced."

Lei and colleagues would like to see researchers, regulators and oil and gas operators work together to better understand what causes injection-induced seismicity in the South Sichuan Basin, to allow effective and safe fracking operations.
-end-


Seismological Society of America

Related Earthquakes Articles:

Can a UNICORN outrun earthquakes?
A University of Tokyo Team transformed its UNICORN computing code into an AI-like algorithm to more quickly simulate tectonic plate deformation due to a phenomenon called a ''fault slip,'' a sudden shift that occurs at the plate boundary.
Earthquakes in slow motion
A survey of slow-slip events in Cascadia reveals new insight into the recently discovered phenomenon.
Earthquakes can be predicted five days ahead
An international team of researchers, which includes physicists from HSE University and the RAS Space Research Institute (IKI), have discovered that, with an impending earthquake, the parameters of internal gravity waves (IGWs) can change five days before a seismic event.
Stanford researchers explain earthquakes we can't feel
Researchers have explained mysterious slow-moving earthquakes known as slow slip events with the help of computer simulations.
Solved: How tides can trigger earthquakes
Some earthquakes along mid-ocean ridges are linked with low tides, but nobody could figure out why.
Measuring iceberg production with earthquakes
An international team led by French researchers from the CNRS and Paris Diderot University came up with the idea of using earthquakes generated when icebergs break away -- felt hundreds of kilometres off -- to measure this ice loss.
Injection wells can induce earthquakes miles away from the well
A study of earthquakes induced by injecting fluids deep underground has revealed surprising patterns, suggesting that current recommendations for hydraulic fracturing, wastewater disposal, and geothermal wells may need to be revised.
Earthquakes can be weakened by groundwater
Researchers from EPFL and the Ecole Normale Supérieure in Paris have found that the presence of pressurized fluid in surrounding rock can reduce the intensity of earthquakes triggered by underground human activities like geothermal energy production.
UH researchers report new understanding of deep earthquakes
Researchers from the University of Houston have for the first time reported a way to analyze seismic wave radiation patterns in deep earthquakes to suggest global deep earthquakes are in anisotropic rocks.
International collaboration studies the predictability of earthquakes
At four centers in California, New Zealand, Europe and Japan -- and in countless labs across the globe -- CSEP's experiments and its rigorous testing procedures have shed light on the predictability of earthquakes, according to a special focus section published June 13 in Seismological Research Letters.
More Earthquakes News and Earthquakes Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

Risk
Why do we revere risk-takers, even when their actions terrify us? Why are some better at taking risks than others? This hour, TED speakers explore the alluring, dangerous, and calculated sides of risk. Guests include professional rock climber Alex Honnold, economist Mariana Mazzucato, psychology researcher Kashfia Rahman, structural engineer and bridge designer Ian Firth, and risk intelligence expert Dylan Evans.
Now Playing: Science for the People

#541 Wayfinding
These days when we want to know where we are or how to get where we want to go, most of us will pull out a smart phone with a built-in GPS and map app. Some of us old timers might still use an old school paper map from time to time. But we didn't always used to lean so heavily on maps and technology, and in some remote places of the world some people still navigate and wayfind their way without the aid of these tools... and in some cases do better without them. This week, host Rachelle Saunders...
Now Playing: Radiolab

Dolly Parton's America: Neon Moss
Today on Radiolab, we're bringing you the fourth episode of Jad's special series, Dolly Parton's America. In this episode, Jad goes back up the mountain to visit Dolly's actual Tennessee mountain home, where she tells stories about her first trips out of the holler. Back on the mountaintop, standing under the rain by the Little Pigeon River, the trip triggers memories of Jad's first visit to his father's childhood home, and opens the gateway to dizzying stories of music and migration. Support Radiolab today at Radiolab.org/donate.