However, they ended up documenting the state’s biggest earthquake in recorded history.
“We didn’t know we were going to go out to record a main shock,” said Holland, a seismologist for the Oklahoma Geological Survey.
The surprise of having such a large quake in Oklahoma, considered geologically stable by most, has not been lost on the public; the substantial seismic event garnered media attention worldwide.
Although some surmised that natural gas exploration may be related to the recent earthquakes, others stated the shake-ups were millions of years in the making.
Whole lotta shakin’
The first earthquake in the recent series was recorded around 2:12 a.m. on Nov. 5, centered in Lincoln County with a magnitude of 4.8, followed over the course of the next few hours by about 15 quakes ranging in magnitude from 2.2 to 3.6, according to the OGS.
That same day, at 10:53 p.m., the big one struck. Measuring 5.6, the quake — also originating in Lincoln County, northwest of Prague and southeast of Sparks — was the largest recorded in the state, breaking the record of an estimated 5.5 near El Reno in 1952. (However, because no seismographs existed in-state at that time, its exact magnitude is uncertain, Holland said.)
The main shock, which was felt as far away as Wisconsin, was followed by dozens of aftershocks over the next few weeks, the largest being a 5.0 on Nov. 8, according to OGS data.
The state Department of Health reported two minor injuries: one in Lincoln County, when a man hit his head while fleeing his home, and another in Pottawatomie County, when a woman cut her foot on broken glass.
In addition, the main shock caused damage to several homes and buildings in Central Oklahoma, as well as to the spires on Benedictine Hall at St. Gregory’s University in Shawnee, several media outlets reported.
The fault where the quakes originated is known as the Wilzetta fault line, Holland said, and while not much was known about it by the general public prior to the quakes, geologists and seismologists have known about it for years.
In fact, Wilzetta was the reason for a 4.3-magnitude earthquake in February 2010, he said.
“That fault is aligned within the regional stress field such that it is more likely to have earthquakes than if it was orientated in a different direction,” Holland said. “The stresses build up over hundreds to tens of thousands of years to generate earthquakes here in Oklahoma.”
The fault is one in a series formed around 300 million years ago, during the intraplate deformation known as the Ancestral Rocky Mountains mountain-building episode.
The Wilzetta fault is what is known as a strike-slip fault, Holland said, similar to California’s San Andreas fault, although on a smaller scale. In a strike-slip, movement is like two bricks lined up side by side, and sliding past each other.
Prior to the most recent quake, the Meers fault in south-central Oklahoma was considered the greatest threat to the state, Holland said. It is the only fault that has produced surface-rupturing earthquakes in the past 3,000 years, he said.
“I certainly knew this (Wilzetta) fault was capable of having earthquakes,” Holland said. “I wasn’t expecting a magnitude 5.6.”
What’s goin’ on?
So what caused the quakes? That’s exactly what Holland and a team of geologists from the University of Oklahoma and Oklahoma State University hope to find out.
The team is currently investigating, and will be studying it for years. However, an early report likely will be out in the beginning of 2012, Holland said, noting there is no evidence to suggest the quake was caused by anything other than natural occurrences.
working hypothesis going into the study is that it was caused by
natural forces, although all possibilities will be thoroughly examined.
right, Damage in the metro was minimal, like a fireplace pulled from a wall in this Edmond home.
going to take time before we can make any determinations like that,”
Holland said. “It’s an important issue for Oklahoma. We have all the
right conditions to have a naturally occurring earthquake. … We have
them in the geologic record, in the historic record, before man was
doing his activities in the area.”
to the U.S. Geological Survey, seismic activity in Oklahoma has
increased in the past few years. From 1972 through 2007, between two to
six earthquakes a year were recorded in Oklahoma, but in 2008, more than
a dozen earthquakes were recorded, according to the USGS. The number of
quakes climbed to around 50 in 2009 and the trend continued in 2010.
have pointed to injection wells and hydraulic fracturing:
energy-industry techniques used to create cracks in gas- and oil-bearing
rock by injecting a high-pressure mixture of water, sand and chemicals
into rock formations. Both are used to increase recovery of fossil
There are approximately 200 injection wells in Lincoln County, said Oklahoma Corporation Commission spokesman Matt Skinner.
But can human activity actually cause earthquakes?
research suggests such a link. In 1967, the U.S. Army Corps of
Engineers and the USGS determined that a deep, hazardous-waste disposal
well at the Rocky Mountain Arsenal near Denver was causing “significant
seismic events,” according to an Environmental Protection Agency report
on injection wells.
a recent report commissioned by drilling company Cuadrilla Resources
confirmed that it was “highly probable” that hydraulic fracking in
northwest England had caused a series of small earthquakes there.
wrote a report published early this year on a series of small
earthquakes in Garvin County, stating that a resident reported about 43
quakes occurring within three and a half miles of a hydraulic-fracturing
project, beginning about seven hours after the first and deepest
fracking project started.
strong correlation in time and space, as well as a reasonable fit to a
physical model, suggest that there is a possibility these earthquakes
were induced by hydraulic fracturing,” the report stated. “However, the
uncertainties in the data make it impossible to say with a high degree
of certainty whether or not these earthquakes were triggered by natural
means or by the nearby hydraulic-fracturing operation.”
gas proponents state there is very little to link the two, and that the
recent earthquake was not caused by natural gas exploration.
During a Nov. 14 forum by the U.S.
House Energy and Commerce Committee, Oklahoma City-based Devon Energy
executive chairman Larry Nichols told members of Congress that he has
serious doubts about whether drilling could cause such a large
reminds me when the Russians put the Sputnik up in the late ’50s, and
the Sputnik was blamed for every evil known to man: earthquakes
tornadoes, whatever,” Nichols said.
Bannister, director of communications for the Oklahoma Independent
Petroleum Association, said hundreds of wells have been drilled in the
state over its history, and it’s impossible to link the recent
earthquake, a single instance, to something that has been happening for
can confidently say Oklahoma’s earthquakes have no relation to drilling
activity,” Bannister said. “If it was the oil and gas industry causing
earthquakes, we’d be having one every day.”