A report issued this month suggests the Mahoning Valley's earthquakes may not be the isolated, random phenomenon previously suspected.
The report states that increased seismic activity has been noted in the Midwest over the past three to four years, and through technological advances, scientists now believe they can link the activity to wastewater injection wells.
Scientists reported that from 1970 to 2000, the region they studied averaged about 20 quakes a year. That rose to about 29 a year from 2001 to 2008 and then jumped each of the next three years to 50, 87 and 134 including several in the Youngstown area that capped off with a 4.0 temblor on New Year's Eve 2011.
The 12 earthquakes last year were believed to be the result of an injection well on Ohio Works Drive in Youngstown. Nearly all of the quakes occurred within a one-mile radius of the well. A report released by the Ohio Department of Natural Resources concluded that the well owned by D&L Energy Systems was in fact drilled into a previously undiscovered geologic fault line.
The ODNR report suggested that the earthquakes were the result of brine water lubricating that fault line and causing it to slip. The New Year's Eve earthquake occurred only one day after D&L took the well offline to study the seismic activity, and there has been a marked absence of earthquakes since then. Gov. John Kasich placed an indefinite moratorium on injection well activity within a five-mile radius of that well, and ODNR said the well will not be permitted to operate again in the future.
The new report mentions the Youngstown quakes, but the scientists say the Valley temblors were no accident.
When USGS scientists first focused on where the Midwest string of quakes occurred, they noticed clusters near injection wells, namely in Colorado and Oklahoma. The use of injection wells has been a common practice for decades and since at least 1986 in Ohio when ODNR reformatted drilling rules. According to the report, the pumping has occasionally created quakes.
Seismologists and drilling industry experts note that there are tens of thousands of waste wells in the country and only a few with problems. However, John Armbruster, a seismologist with Columbia University, insists there need to be more instruments near waste wells for monitoring purposes.
There are 171 operating brine injection wells in Ohio.
Columbia's Lamont-Dougherty Geologic Observatory placed several seismographs in the area and its findings contributed to ODNR's March report.
Armbruster has monitored the D&L well since the last quake and said the cessation of quakes since the well came offline suggests that it was causing the activity.
He said Youngstown's problem was no freak occurrence, citing data that reveals more than a dozen small quakes in Marietta over the past year-and-a-half. Like Youngstown, Marietta is not a seismically active part of the state but has several injection wells.
Evidence that suggests a link between quakes and injection wells is continually being reported from around the country. Seismologist Steve Horton at the University of Memphis studied a series of quakes along a fault in Arkansas in 2010 and 2011.
Horton said like Youngstown, the Arkansas earthquakes also ended shortly after the wells there were taken offline.
Still, Armbruster admitted that scientists have not looked carefully enough to know what percentage of wells would be causing seismic activity, and Horton added to the discussion.
"You need to be within 10 kilometers and the fault needs to be critically stressed, and we don't know exactly what the distribution of critically stressed faults is in the United States," Horton said. He added there also needs to be a route for the fluid to travel to reach the fault, which is not always present.
Following the March report, ODNR began drafting legislation to tighten rules on injection wells.