It is important to put seismic activity in general and seismic activity in natural gas development areas into context. Minor and imperceptible seismic activity is extremely common. For instance, roughly 1.3 million 2-2.9 magnitude quakes happen every year around the world. You can visit the U.S. Geological Survey site to see seismic activity that is taking place every day.
There is a difference between Class II disposal injection wells and hydraulically fractured wells and many media reports confuse the two. Hydraulic fracturing operations are routinely conducted throughout the country: In the last 60 years, the Society of Petroleum Engineers estimates that hydraulic fracturing has been employed on more than one million U.S. wells.
There are nearly 150,000 disposal injection wells in America, with only a handful potentially linked to modest seismic events. Industry is cooperating with ongoing investigations with regard to these wells.
Steps being taken to prevent seismic events include limiting increases in well pressure by reducing either the amount of water pumped into the wells or the rate at which it is pumped.
Regulators in Ohio and Arkansas are looking at a possible connection between minor events and disposal of water in injection wells. These are very different from gas-producing wells.
The use of injection wells is regulated under the Underground Injection Control (UIC) Program established in the 1974 Safe Drinking Water Act. EPA administers the UIC program and delegates authority to states. Most states are responsible for permitting, but the standards for construction, maintenance and monitoring of these wells are set by EPA.
Regarding hydraulic fracturing, Stanford University geophysicist Mark Zoback stated "As there has been an appreciable increase in hydraulic fracturing associated with shale gas development in recent years, it should be pointed out that the water injection associated with hydraulic fracturing is not responsible for the triggered seismicity in question."
In response to press attention focused on the release of a brief abstract of a U.S. Geological Survey study expected to be released this summer, Bill Ellsworth, a lead author of the report stated that "there's almost no relationship between hydraulic fracturing and earthquakes. And this has really been a problem in the media confusing the process of stimulating the reservoirs so they produce gas. This does not produce earthquakes that are of concern."
Hydraulic fracturing of natural gas wells was not being conducted in the areas in northeastern Ohio at the time of the recent earthquake. In fact, northeastern Ohio has experienced similar - even greater - seismic activity long before oil and gas development and long before disposal wells were employed in the area.
Evidence shows the November 2011 earthquakes in Oklahoma were unrelated to natural gas operations. Rather, they correlate to a previously identified geologic fault known to be seismically active in the past. In fact, experts have said that hydraulic fracturing, or any man-made activity, could not have caused an event as powerful as those that occurred in Oklahoma.
One of the earthquakes measured 5.6 on the Richter scale. A 5.5-magnitude earthquake occurred in the same place in Oklahoma in 1952, predating hydraulic fracturing. The earthquakes occurred along the well-known and deep Wilzetta Fault.
Technical experts, including authors of an Oklahoma Geological Survey study, which dealt with minor events that occurred early in 2011, have clearly stated it is "impossible to say with a high degree of certainty" what caused the seismic activity at issue.
1,047 earthquakes of varying degree were recorded in Oklahoma in 2010 alone. Fewer than 10% actually were felt by residents.