WASHINGTON - Injection wells that pump wastewater into the earth's core have raised earthquake risks in parts of the central United States to the same level as sections of California along the San Andreas fault, a new federal study says.
The U.S. Geological Survey this week released its first maps of areas that are prone to earthquakes because of human activities. It found that roughly 7 million people live and work in sections of the central and eastern U.S that are subject to "damaging shaking" from man-made quakes.
Perry, Ashtabula and Youngstown are among the 21 hot-spots the survey identified as vulnerable to human-induced earthquakes. Ohio's tremor risks aren't as great as parts of Oklahoma, Kansas, Texas, Colorado, New Mexico and Arkansas where quakes have escalated dramatically since 2008.
The number of earthquakes of 3.0 magnitude or larger in those areas soared from an average of 24 each year before 2009 to 1,010 in 2015, the study said. Through mid-March, that region experienced 226 tremors. The study's authors attributed the rise to wastewater disposal, although they stressed that most injection wells aren't associated with earthquakes.
In Ohio, the study said tremors from man-made causes decreased in recent years, though it offered no explanation why. Survey representatives did not respond to emailed questions on the issue.
How serious is the risk here?
The study said there weren't any quakes of 2.7 magnitude or higher in Northeast Ohio last year and there were just two the prior year, both in the Youngstown area. For that reason, it predicted there's no great risk of man-made earthquakes this year in northeast Ohio.
"Our assessment of induced earthquake hazard was dependent on the assumption that past earthquake rates will remain constant over the next year of the forecast," the study said.
Ohio Department of Natural Resources spokesman Eric Heis said most Ohio earthquakes have natural causes and cases of "induced seismic activity" are extremely rare in the state. He said they're typically linked to underground injection wells that are suspected of stimulating micro-faults miles beneath the earth's surface, he said.
ODNR has tried to address potential problems by imposing 2014 regulations that require horizontal production wells or Class II injection wells within 3 miles of a geological fault or area with seismic activity to install seismic monitors, Heis said.
How do injection wells contribute to earthquakes?
Injection wells put fluids such as brine into deep underground porous geological formations. The wells are used for a variety of purposes, including waste disposal, mining, and disposal of wastewater generated by the oil and gas extraction process known as "fracking."
Faults that run under the earth's crust can usually sustain high stress without slipping because they're pushed together by heavy surface rocks. According toUSGS, injected wastewater contributes to earthquakes by counteracting the friction that keeps the rocks from slipping, effectively prying them apart.
What's the risk near the Perry nuclear plant?
One of the largest earthquakes ever to occur in Ohio happened near FirstEnergy's Perry nuclear power plant in 1986. According to ODNR, that 4.6-magnitude upheaval was the first earthquake in the state for which injuries were recorded, and the nearest earthquake to a U.S. nuclear power plant.
The risk that an earthquake would cause a severe accident at a U.S. nuclear plant is greater than previously thought, 24 times as high in one case, according to an AP analysis of preliminary government data. And that one case is the Perry 1 nuclear reactor east of Cleveland in Lake County.
According to the state, several geologists were concerned that earthquake was induced by a well nearby well that was injecting liquid wastes from agricultural manufacturing more than a mile underground.
FirstEnergy spokeswoman Jennifer Young said the earthquake occurred before the plant was operational and the only damage it caused at the plant was to ceiling tiles that fell from an office area.
She said the plant is designed to withstand seismic activity from any source, and has never had to shut down because of earthquakes.
After an earthquake and tsunami damaged Japan's Fukushima nuclear plant five years ago, she said the Perry plant was required to do a seismic risk evaluation that found it can "safely withstand any ground movement expectations in our area."
http://www.cleveland.com/metro/index.ssf/2016/04/feds_outline_northeast_ohios_m.html
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