A fracking waste disposal well linked to 11 earthquakes that rocked the Youngstown area was the likely source of at least 98 additional temblors that were too weak for people to notice, according to new research.
They were discovered by Columbia University researchers who analyzed data collected by Ohio’s regional network of seismometers. The first was a magnitude 1.1 quake that occurred on Jan. 11, 2011, two weeks after the Northstar No. 1 well started injecting fracking waste underground.
The earthquakes were so weak they didn’t trigger alarms until March 17, 2011, when a magnitude 2.1 earthquake was followed minutes later by magnitude 2.6 earthquake.
Nine additional earthquakes were detected in the following months. They culminated in a magnitude 4.0 earthquake on Dec. 31 that drew national attention and led to new government safety standards for Ohio’s growing fracking-waste-disposal industry.
The well shut down the day before that earthquake.
The study, recently published in the Journal of Geophysical Research: Solid Earth, offers the most-compelling evidence yet that the Northstar well repeatedly triggered some unknown fault line beneath Youngstown. Among other things, the epicenters of the earthquakes moved west over time, conceivably as the injected wastes spread underground.
“In January and February, the earthquakes were near the injection well. By December, it was nearly a mile away,” said Won-Young Kim, a Lamont-Doherty Earth Observatory senior research scientist and the study’s author. In addition, earthquake activity dropped off during holiday weekends when the well was inactive, Kim said.
Most of the temblors ranged from magnitude 0.5 to nearly magnitude 2.0.
“Even at (magnitude) 2, sometimes people don’t feel it unless they are right on top of it,” said Michael Hansen, the state’s seismologist. “These are tiny quakes.”
Hansen and Kim said the state’s network of seismometers is generally unable to detect earthquakes weaker than 2.0 because their signals are concealed by other vibrations, including those created by cars and trucks on the surface. Kim said he used the signals created by the larger Youngstown earthquakes as a template to find the smaller, undetected temblors.
Officials with D&L Energy, the Youngstown company that owned the Northstar well, declined to comment.
The Youngstown quakes haven’t deterred businesses from drilling new fracking waste wells. Since December 2012, the number of active disposal wells in Ohio has increased from 179 to 188.
Mark Bruce, a spokesman for the Ohio Department of Natural Resources, said new safety standards forbid new disposal wells from being drilled to a layer of crystalline ‘basement rock,’ which has been determined to be a risk for new earthquakes.
Disposal wells also cannot be drilled to a layer of sandstone just above that basement layer until the state monitors the area with sensitive seismometers that regulators purchased after the Youngstown earthquakes. The seismometers remain in place for months before a well is drilled, to create a baseline of seismic activity, and then stay in place after the well opens to see if there are changes.
Six such seismometers are monitoring seven wells in Mahoning, Muskingum, Trumbull, Tuscarawas and Washington counties. So far they’ve detected no problems, Bruce said.