U.S. to Map the Risks of Man-Made Earthquakes
Move Follows Rise in Frequency of Quakes in Regions With
Wall Street Journal
1 May 2014
By Tamara Audi
ANCHORAGE, Alaska—A rise in the frequency of earthquakes in
regions with increasing oil and gas extraction is prompting
scientists for the first time to assess risks of man-made quakes
and include them on federal maps that influence building codes and
The new mapping, which the U.S. Geological Survey hopes to release
later this year, is likely to put regions of the central U.S. not
typically thought of as earthquake zones on notice for greater
seismic hazards. Unlike West Coast states at high risk for major
quakes, like California, other areas typically aren't as prepared
to handle strong temblors.
The USGS regularly maps hazards from naturally occurring quakes,
alerting building engineers and local governments to the
probability of moderate and strong shaking in their regions based
on fault lines and seismic studies. The agency said that in the
wake of research showing increased seismic activity in certain
regions—including two strong 2011 quakes in Colorado and
Oklahoma—it decided to release a separate map to evaluate the risk
of man-made quakes, called induced quakes.
"We've never done this before," said Justin Rubinstein, a USGS
seismologist working on the assessment. "We've never tried to
consider induced earthquakes in hazards."
An average rate of more than 100 earthquakes a year above a
magnitude 3.0 occurred in the four years from 2010 to 2013 in the
central and eastern U.S., compared with an average rate of 20
events a year observed from 1970 to 2000, according to the USGS.
"The number of earthquakes within central and eastern United
States has increased dramatically over the past few years,
coinciding with increased hydraulic fracturing," or fracking, and
the subterranean disposal of wastewater from oil extraction, said
the Seismological Society of America, an organization of quake
scientists, at its meeting here on Thursday.
Mr. Rubinstein said the USGS remains "agnostic" on the causes of
the increase. "We're not here to point fingers," he said, adding
that "an increase in earthquake rate" for any reason "implies that
the probability of a larger earthquake has also risen."
Greater hazard risks could prompt communities to better prepare
for quakes, or increase insurance costs.
There generally is an accepted link between quakes and human
activity, but there is debate about which specific activities and
sites might cause temblors, and how large an induced quake might
"It's very complicated and difficult to assess whether a quake is
induced or not," said Hal Macartney, a geologist who works in the
oil and gas industry. "There's still a lot of uncertainty." He
added that the industry is attuned to the issue, and some
operators have installed their own monitors to measure quakes and
try to figure out "how to mitigate" any potential risks.
Gail Atkinson, a professor of earth sciences at Western University
in Ontario, Canada, said induced quakes can cause more intense
shaking on the surface because they tend to occur at shallower
depths than many naturally occurring quakes. But she and other
scientists said more access to data from regulators and industry
operators is needed to fully understand the risks.
The mapping effort comes as regulators, industry officials,
politicians and scientists begin to grapple with how to measure
and respond to potential quake risks from human activities in the
aftermath of a jump in seismic activity in Oklahoma, Texas,
Arkansas, Ohio and Colorado.
Last month, Ohio state officials said they believed the "likely
source" of a series of small quakes there was fracking activities.
Ohio will require additional seismometers to more closely monitor
Other states are focused on how wells used to inject fluids deep
underground and dispose of millions of gallons of fracking
wastewater might be contributing to quakes.
Wastewater disposal after oil extraction appears to cause larger
quakes than fracking, researchers said. In that process, oil is
extracted with salt water. The remaining brine, or wastewater, is
injected into the ground. The pressure caused by that can put
stress on an existing faults and trigger quakes, some scientists
In 2011, wastewater disposal appears to have caused a magnitude
5.3 quake in Colorado and a 5.6 quake in Prague, Okla., the USGS
said. That quake caused light damage to more than a dozen homes in
A spokesman for the American Petroleum Institute didn't
immediately respond to a request for comment. In the past, the
group has said there is not enough data to confirm a link between
tremors and injection wells.
Scientists and industry officials estimate there are about 35,000
wastewater wells in the U.S. A small fraction of those are
believed to be linked to quakes, seismologists said.
On Thursday, new research unveiled at the Seismological Society of
America conference said that quakes can be triggered up to 30
miles away from the site of wastewater disposal, a greater
distance than previously thought, said Katie Keranen, an assistant
geophysics professor at Cornell University who led the study.
—Russell Gold contributed to this article.
Write to Tamara Audi at email@example.com