Fracking Earthquakes!

Earthquakes in Arkansas May Be Man-Made, Experts Warn

The sudden swarm of earthquakes in Arkansas -- including the largest quake to hit the state in 35 years -- is very possibly an after effect of natural-gas drilling, experts warn.

At issue is a practice called hydraulic fracturing, or "fracking," in which water is injected into the ground at high pressure to fracture rock and release natural gas trapped within it.

Geologists don't believe the fracking itself is a problem. But Steve Horton, an earthquake specialist at the University of Memphis and hydrologic technician with the U.S. Geological Survey, is worried by a correlation between the Arkansas earthquake swarm and a side effect of the drilling: the disposal of wastewater in injection wells...

The theory goes that the fluids being injected are lubricating the stresses in the rocks, leading to the quakes.  There is some activity in the mid section of the country, not much compared to say, California, but the New Madrid seismic zone, in the region where Missouri, Tennessee and Arkansas meet is active, and produced a major quakes in 1699 and 1811-1812.  Geology shows previous pre-historical large quakes.

Could the stresses that lead to earthquakes be, in part, relieved by the lubrication from fracking waste disposal, and could that forestall or even prevent later major quakes in the region?  Or the quakes could just be natural:

Scott Ausbrooks, geohazards supervisor for the Arkansas Geological Survey, said the quakes are part of what is now called the Guy earthquake swarm — a series of mild earthquakes that have been occurring periodically since 2009. A similar swarm occurred in the early 1980s when a series of quakes hit Enola, Ark.

Ausbrooks said geologists are still trying to discover the exact cause of the recent seismic activity but have identified two possibilities.

"It could just be a naturally occurring swarm like the Enola swarm, or it could be related to ongoing natural gas exploration in the area," he said.