An alert skytruther, who describes himself as a retired city environmental health director, gave us a heads up that a moderate (magnitude 3.9) earthquake shook residents along the Colorado - Utah border near the Paradox Valley late last night. He also passed along a link to the USGS information page on this earthquake. This statement caught our eye:
The largest historical earthquakes were a M4.4 in 2000 near the Paradox Valley in western Colorado and a M4.3 in 1953 near Green River, Utah. The M4.4 earthquake in 2000 and many smaller earthquakes in the Paradox Valley were induced by brine injection in deep wells."Brine" is drilling-industry lingo for the non-hydrocarbon fluids that are produced by oil and gas wells. This is mostly water by volume, but often includes toxins -- metals and salts leached from deep bedrock, residual chemicals used in drilling and fracking the well, and low levels of radioactivity. Getting rid of this stuff by pumping it back into the bedrock is an increasingly common practice as the current national shale-gas and shale-oil drilling booms are producing large amounts of wastewater that in some places threaten to overwhelm the current disposal infrastructure.
This method of disposal has been proven for decades to cause small to moderate earthquakes, and is strongly implicated in recent earthquake swarms in Ohio, Oklahoma, Colorado and Arkansas. We suspect this shallow quake (1.2 km depth) is possibly the latest example of an earthquake related to oil and gas activity.
So far the only known example of earthquakes caused by the hydraulic fracturing operation itself, is from Lancashire, England in 2011. Given the number of disposal wells and fracking operations, induced seismicity due to oil and gas development remains a relatively rare occurrence, but as one scientist puts it "an earthquake even of magnitude 4 in a populated area can be an unpleasant thing." Indeed.