In recent years, earthquake rates in regions of the historically seismically quiet central and eastern U.S. have risen at a remarkable pace. According to the latest research and scientific consensus, the culprit stems from impacts of wastewater disposal or enhanced oil recovery processes in deep injection wells—common procedures in oil and gas production.
Executive SummaryAIR Worldwide's Dr. Claire Pontbriand describes some of the developing science behind induced earthquakes and hydraulic fracturing. She explains that it's not the initial fracking activity but the reinjection of wastewater fluids into disposal wells that is of greater concern in terms of increased earthquake risk. Fluid pressure diffusing from the wastewater injection activities can increase pore pressure along existing nearby faults, bringing them close to rupture.
In September 2016, a magnitude 5.8 earthquake near Pawnee represented the largest recorded earthquake in Oklahoma. The M5.7 2011 Prague, Okla., earthquake resulted in insured losses in excess of $10 million, and other potentially induced earthquakes have resulted in damage.
There are many questions surrounding these events in assessing their hazard and risk. What is the maximum possible magnitude of earthquake? What risk does future seismicity—the occurrence and distribution of earthquakes—pose to exposure in the central and eastern U.S.?
Most induced temblors are small, but they have been occurring in greater numbers and larger events have been recorded. In addition, considering what we know about seismotectonics—the relationship between historical earthquakes, faults and rock deformations driven by the active processes of plate tectonics—in the region, we cannot rule out the possibility of M7.0 or larger earthquakes in the central and eastern U.S.