According to a new United States Geological Survey (USGS) report, states like Colorado are now more prone to earthquakes than ever before. But tectonic forces are not to blame. Instead, Colorado and other states face a statistically higher chance of an earthquake due to the U.S.’s insatiable thirst for fossil fuel.
For the first time, the USGS released a one-year earthquake forecast including naturally occurring earthquakes along with those induced by human activity (see map). While society at large may be alarmed to learn that human activity can cause earthquakes, this is a phenomenon that the seismic community has known about for years.
Wastewater injection deep into the Earth’s crust is the main reason for the spike in earthquake frequency. It is a common practice in the oil and gas industry for companies looking for a cheap, quick way to get rid of their byproducts. Dirty water injected into the Earth passes through rocks, which act as a filter for the fluid. When the water returns to the surface, it is newly cleansed, going through roughly the same process as well water.
However, as was discovered first in Commerce City, Colo., at the Rocky Mountain Arsenal during the 1970s, the Earth is no pushover. Pump enough pressure into it, and it will fight back.
As Colorado College’s resident geophysicist, Megan Anderson explains there are many faults sitting far beneath the Earth’s surface. The immense stress from the weight of the crust above these rocks acts a peacekeeper between the rocks on both sides of the fault. Both rocks experience the same amount of “lithostatic pressure” from the above crust, so neither moves.
The fault sits stagnant, causing no seismic ruckus on Earth’s surface. However, when people inject water into the Earth, they introduce new pressure on one side of the fault, disrupting the balance and resulting in a minor earthquake.
This is the first time that the USGS has released a seismic-hazard forecast in a one-year timespan. Usually, it predicts earthquakes within a 50-year period. However, as the nation, namely the Central and Eastern U.S., has seen a huge increase in seismic activity coinciding with the beginning of the so-called “shale revolution” (see below), the USGS decided upon a one-year forecast. Earthquake occurrences are now as much at the mercy of year-to-year variables, like changes in public policy and gas prices, as they are of geological forces.
According to the USGS report, Oklahoma, Kansas, Texas, New Mexico, Arkansas, and Colorado are predicted to experience the most human-induced earthquakes. In Colorado, earthquake damage is forecasted to occur on the southern border with New Mexico, where the resource-rich Raton Basin lies.
Colorado knows the shale revolution as well as any state. In 2013, an “earthquake swarm” occurred in the Raton Basin, an event that is the result of dozens of strikes on the same area in a short period of time. This swarm was concentrated around wastewater injection sites and included Colorado’s largest earthquake since 1967.
Meanwhile, in May of 2014, Greeley, Colo., experienced a 3.4 magnitude earthquake, which seismologists traced back to a single wastewater injection site. These once rare earthquakes, coupled with accidents like the fire that broke out on a wastewater injection site last spring, have embroiled Greeley and other Colorado towns in the debate of whether or not the economic gains from drilling and fracking outweigh the environmental fallout.
The intention of the seismologists behind this report, however, is not to add ammunition to the anti-gas and oil extraction side of the argument. Instead, they hope that communities and towns who now find themselves in the crosshairs of seismic hazards do not get caught with their earthquake-pants down.
“The new report can be used by both government officials to make more informed decisions and by emergency response personnel to assess vulnerability and provide safety information to those who are in potential danger,” reads a statement from the USGS.
The moral of the story: if you are going to the Raton Basin, be sure to wear your hardhat.
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