Great
Earthquakes In Diverse Places
10 aftershocks follow 5.6 Earthquake in Oklahoma
SPARKS, Okla. (AP) – Oklahoma residents more accustomed to
tornadoes than earthquakes have been shaken by weekend temblors
that cracked buildings, buckled a highway and rattled nerves. One
quake late Saturday was the state's strongest ever and jolted a
college football stadium 50 miles away.
Many homes and other buildings cracked and suffered minor damage,
there were no reports of severe injuries.
Saturday night's earthquake jolted Oklahoma State University's
stadium shortly after the No. 3 Cowboys defeated No. 17 Kansas
State.
"That shook up the place, had a lot of people nervous," Oklahoma
State wide receiver Justin Blackmon said. "Yeah, it was pretty
strong."
The magnitude-5.6 earthquake late Saturday was Oklahoma's
strongest on record, said Jessica Turner, a geophysicist with the
U.S. Geological Survey. Centered near Sparks, 44 miles northeast
of Oklahoma City, it could be felt throughout the state and in
Arkansas, Kansas, Missouri, northern Texas and some parts of
Illinois and Wisconsin. It followed a magnitude-4.7 quake early
Saturday that was felt from Texas to Missouri.
The weekend earthquakes were among the strongest yet in a state
that has seen a dramatic, unexplained increase in seismic
activity. Oklahoma typically had about 50 earthquakes a year until
2009. Then the number spiked, and 1,047 quakes shook the state
last year, prompting researchers to install seismographs in the
area. Still, most of the earthquakes have been small.
Geologists now believe a magnitude-4.7 earthquake Saturday morning
was a foreshock to the bigger one that followed that night. They
recorded 10 aftershocks by midmorning Sunday and expected more.
Two of the aftershocks, at 4 a.m. and 9 a.m., were big,
magnitude-4.0.
"We will definitely continue to see aftershocks, as we've already
seen aftershocks from this one," said Paul Earle, a seismologist
with the USGS in Golden, Colorado. "We will see aftershocks in the
days and weeks to come, possibly even months."
Several homeowners and businesses reported cracked walls, fallen
knickknacks and other minor damage. Brad Collins, the spokesman
for St. Gregory's University in Shawnee, said one of the four
towers on its "castle-looking" administration building had
collapsed and the other three towers were damaged. He estimated
the towers were about 25 feet tall.
In Sparks, Joe Reneau said clouds of dust belched from the corners
of almost every room in his house and a roar that sounded like a
jumbo jet filled the air. Reneau's red-brick chimney collapsed and
fell into the roof above the living room. By the time the shaking
stopped, a pantry worth of food had been strewn across the kitchen
and shards of glass and pottery covered the floor.
"It was like WHAM!" said Reneau, 75, gesturing with swipes of his
arms. "I thought in my mind the house would stand, but then again,
maybe not."
An emergency manager in Lincoln County near the epicenter said
U.S. 62, a two-lane highway that meanders through rolling
landscape between Oklahoma City and the Arkansas state line,
crumpled in places when the stronger quake struck Saturday night.
The crowd of nearly 59,000 was still leaving Oklahoma State's
Boone Pickens Stadium when the earthquake hit, and players were in
the locker rooms beneath the stands. The shaking seemed to last
the better part of a minute, rippling upward to the stadium press
box.
"Everybody was looking around, and no one had any idea," Oklahoma
State quarterback Brandon Weeden said. "We thought the people
above us were doing something. I've never felt one, so that was a
first."
A few hours before dawn Sunday, the latest quake set nerves on
edge anew.
Jessie Plumb, a registered nurse at Prague Community Hospital,
said she and other staffers felt the magnitude-4.0 quake while on
the second floor of the building.
"It kind of gave a little bit of a shake, a little bit of rock 'n
roll," she said by telephone. "I would say it was 20 or 25
seconds."
Oklahoma has had big earthquakes before. USGS records show a
magnitude-5.5 earthquake struck El Reno, just west of Oklahoma
City, in 1952.
Turner said an active spate of earthquakes started in the region
in February 2010 and the latest activity appears to be part of
that trend. But experts are still puzzling out why the latest
quakes have been concentrated in such a small geographic area
around Sparks, she said.
Scientists say they have no explanation for the quakes. They
happened along an ancient fault, although it's not clear yet
whether shifting along the fault is what caused them, Earle said.
One reason earthquakes are hard to predict in Oklahoma is that the
state sits over a series of smaller ancient faults, rather than a
major fault, such as California's San Andreas Fault, he said.
Arkansas also has seen a big increase in earthquake activity,
which residents have blamed on injection wells. Natural gas
companies engaged in hydraulic fracturing, or fracking, use fluid
to break apart shale and rock to release natural gas. Injection
wells then dispose of the fluid by injecting it back into the
ground.
There are 181 injection wells in the Oklahoma county where most of
the weekend earthquakes happened, said Matt Skinner, spokesman for
the Oklahoma Corporation Commission, which oversees oil and gas
production in the state and intrastate transportation pipelines.
But natural gas companies claim there is no proof of a connection
between injection wells and earthquakes, and a study released
earlier this year by an Oklahoma Geological Survey seismologist
seems to back that up. It found most of the state's seismic
activity didn't appear to be tied to the wells, although more
investigation was needed. The state survey didn't respond to phone
messages left Sunday.
Earle said he couldn't comment on the relationship between
fracking, injection wells and earthquakes.