The relationship between injection wells and earthquake generation in the Denver Basin was noted by geologist David Evans in the a960s. The Rocky Mountain Arsenal was disposing of liquid wastes by deep-well (c. 12,000 feet) injection. The occurrence of small-magnitude EQs was noted after the injection began. Evans noted a relationship between the volume of fluid injected and the EQ frequency.
Evans, David M. 1966. The Denver area earthquakes and the Rocky Mountain Arsenal disposal well. The Mountain Geologist. 3(1):23 26.
The injected fluids serve to increase the subsurface fluid pressure which decreases the effective stress (which tends to keep rocks from moving along faults); this increase in fluid pressure makes the rocks on either side of a fault more likely to move relative to each other.
Here's a fact sheet from the RMA (not very informative) but it provides a seminal reference is given:
Hsieh, Paul A., and John D. Bredehoeft, 1981. A reservoir analysis of the Denver earthquakes: a case of induced seismicity. Journal of Geophysical Research, 86 (B2): 903-920.
John Bredehoeft is no stranger to WaterWired. I have referred to him a number of times. He is arguably the greatest living hydrogeologist. He recognized the significance of the Denver Basin earthquake-injection well nexus and posited that earthquakes could be controlled b cycles of fluid injection/withdrawal.
From his WWW page.
Bredehoeft did the reservoir engineering for the USGS earthquake control experiments at Rangely, Colorado. Working with Raleigh and Healy, they controlled earthquakes at Rangely. The experiment entailed two cycles: 1) turned earthquakes off, 2) turned them on again, and 3) finally off. This is the only field scale experiment to demonstrate the Hubbert/Rubey hypothesis of effective stress in controlling earthquakes.
Raleigh, C.B., J.H. Healy, and J.D. Bredehoeft, 1976. An experiment in earthquake control at Rangely, Colorado. Science, 191(4233): 1230-1273.
Here's the abstract:
An experiment in an oil field at Rangely, Colorado, has demonstrated the feasibility of earthquake control. Variations in seismicity were produced by controlled variations in the fluid pressure in a seismically active zone. Precise earthquake locations revealed that the earthquakes clustered about a fault trending through a zone of high pore pressure produced by secondary recovery operations. Laboratory measurements of the frictional properties of the reservoir rocks and an in situ stress measurement made near the earthquake zone were used to predict the fluid pressure required to trigger earthquakes on preexisting fractures. Fluid pressure was controlled by alternately injecting and recovering water from wells that penetrated the seismic zone. Fluid pressure was monitored in observation wells, and a computer model of the reservoir was used to infer the fluid pressure distributions in the vicinity of the injection wells. The results of this experiment confirm the predicted effect of fluid pressure on earthquake activity and indicate that earthquakes can be controlled wherever we can control the fluid pressure in a fault zone.
Here is the show from KCRW; it runs about 13 minutes. First, a summary of the show.
The Natural State
There's a modern day gold rush in Faulkner County, Arkansas... this one, for natural gas. Since 2005, more three thousand natural gas wells have been drilled in the area. Each of these wells was hydro-fractured or “fracked,” a controversial technique in which millions of gallons of water – and some chemicals - are injected into the shale, breaking the rock and allowing extraction of embedded natural gas. In the town of Greenbrier the natural gas industry has benefited plenty of people. But in recent months, residents have had to contend with another, absolutely unexpected boom. A swarm of mysterious earthquakes began last fall along an ancient and heretofore unknown fault.
Musician Bonnie "Prince" Billy, also known as Will Oldham contributed an original song called "Mother Nature Kneels."
Bonus added on 12 June 2011: Former DHS Secretary and Pennsylvania governor Tom Ridge talks fracking and natural gas on the Colbert Report. http://t.co/snC75IZ
"So the arguments for and against tobacco industry are comparable to that of the hydrofracking and natural gas industry." -- Think Before You Frack!!