26th April (UPI) – Scientists have found more evidence linking fracking to earthquakes, this time in the central and eastern United States.
At the 2019 Seismological Society of America meeting held in Seattle this week, the researchers further developed the link between hydraulic fracturing wells and about 600 earthquakes in Ohio, Pennsylvania, West Virginia, Oklahoma, and Texas.
Previous studies have described in detail the relationship between oil and gas operations and earthquakes in Oklahoma, Canada and China. However, these studies focused mainly on the relationship between sanitation and seismic activity.
In hydraulic fracturing, high pressure fluids are injected deep into rock (mostly shale) to trigger the release of oil and gas rock strata. Often, the effluent remaining from the activity is treated and then injected back into the soil. The layers from which oil and gas are extracted are wetter in areas such as Oklahoma, resulting in larger volumes of wastewater and increased disposal costs.
In states like Ohio, Pennsylvania and West Virginia, hydraulic fracturing wells are more common than wastewater injections. Fountains in Appalachia have become increasingly common in the last decade.
"The wells are at a greater distance when they are active, and there is not so much sanitation," said Michael Brudzinski of Miami University, Ohio, a press release. "So you can see more accurately and directly when sanitation creates seismicity and when hydraulic fracturing in the Appalachian basin produces seismicity."
Brudzinski and his colleagues used a method known as "Multi-Station Template Matching" for the signature of small, flat quakes. They compared the timing of seismic signatures with the schedule of regional fracking operations.
"The [fracking] seismic signature, if you look at it in some sort of timeline, shows these bursts of seismicity, hundreds or sometimes thousands of events over a few days or weeks, and then it's quiet again tend to this pattern in sanitation, "Brudzinski said.
The research team is currently investigating the relationship between different fracking variables ̵
"The one we remember most is that the depth of the well is more tied to the probability of seismicity than we expected," said Brudzinski.