A new study  out in Science  by US Geological Survey scientist William Ellsworth links earthquakes to wastewater injection sites. These earthquakes, thought to be caused by pressure changes due to excess fluid injected deep below the surface, are being dubbed “man-made” earthquakes.
It's not the first time scientists have used that moniker, as earthquakes have been associated with other industrial operations that mess with underground formations such as surface and underground mining or dams that impound water into reservoirs.
Yet, in more recent years, we're seeing more and more of them,
“The number of earthquakes has increased dramatically over the past few years within the central and eastern United States. More than 300 earthquakes above a magnitude 3.0 occurred in the three years from 2010-2012, compared with an average rate of 21 events per year observed from 1967-2000.”
Many likely know that “wastewater” is a byproduct of many fossil fuel processes . It can come from raw material itself or is a leftover from purification steps during the extraction and processing phases of fuel production. To illustrate a few examples, during coal processing, some coal gets washed in order to remove materials and other impurities. Many companies  dub this under the misnomer “clean coal” because it is “cleaned” before it is combusted, leaving the combustion process with less “pollution”. But the companies that tout “clean coal” conveniently leave out the wash water, affectionally named “coal slurry ”, which contains a lot of the toxic leftovers.
Tar sands extraction likewise uses massive amounts of water to help separate the bitumen from the sand. And, in gas fracking, water used in the wells to frack the rock and extract the gas (along with whatever chemicals are mixed in with it) must also be properly disposed of. Fracking wastewater was found to be the culprit of the earthquakes in Youngstown, OH  where an injection site was near a fault line.
Companies take this toxic wastewater and inject it deep into the ground to avoid contaminating the water table. However, the new USGS study found that the risk of earthquakes is not actively assessed at injection sites, nor monitored. And if wastewater is injected near fault lines, the risk becomes much higher.
While they say that the practice of fracking itself may not be enough to cause mega-earthquakes, wastewater injection sites can have the potential to be very destructive. In one case, an earthquake with a 5.6 magnitude destroyed 14 homes and injured two people in central Oklahoma. A 5.6 earthquake in an urban area would obviously cause much more severe and widespread consequences.
Let's face it, there's already a mountain of evidence as to why fracking  is unsafe and unsuitable - this new nugget of information is more akin to almonds on top of an already piled-on ice cream sundae. But, that doesn't stop the other side from trying to trivialize. From Marcellus Drilling News :
Lessons and Observations:
1. An injection well caused the Youngstown earthquake (several earthquakes), not a fracked natural gas well. Injection wells dispose fracking wastewater–so while there is a connection with fracking, the earthquakes were not “caused by” fracking.
2. The Youngstown injection well in question was located over a previously unknown seismic fault. The pressure of the fluid working its way into the fault is what caused the earthquakes.
3. When it became known there was a fault and the injection well was causing the earthquakes, the well was shut down permanently.
4. That’s one well out of 2,455, or .04% (four-tenths of one percent) by our mathematical reckoning. Statistically speaking–zero.
Drilling for natural gas (and oil) in shale is an industrial process and has risks. Earthquakes, for all intents and purposes, are not one of those risks. Not in any meaningful way.
Ok, great, the USGS blog did specifically point out that the earthquakes weren't due to the drilling process - so we can give you a cookie for that. However, the wastewater is a product of the fracking process, ipso facto, it's caused by fracking. The USGS study is precisely pointing out that there is no consideration for earthquake risk when injecting wastewater, and perhaps there should be. The data that is turned in from injection sites is not even adequate enough to assess this risk at the current moment. From USGS:
“… one consequence is that both the quantity and timeliness of information on injection volumes and pressures reported to the regulatory agencies is far from ideal for managing earthquake risk from injection activities. Thus, improvements in the collection and reporting of injection data to regulatory agencies would provide much-needed information on conditions potentially associated with induced seismicity.”
I'm sure the people who lost a home or sustained significant damage from an earthquake that was preventable in the first place would consider these risks meaningful.