As many as 10,000 people reported feeling tremors across much of Oklahoma, except the panhandle, and North Texas, said a seismologist for the U.S. Geological Survey.
The reports were made on the USGS website, earthquake.usgs.gov, said Earle, of the USGS Earthquake Center in Golden, Colo.
Earle said Wednesday's quake was "deeply buried with no surface expression," but no major damage was reported anywhere by 10 a.m.
Earlier reports stated the quake registered 4.5, but that was downgraded later to 4.3, Earle said.
There were no immediate reports of damage or injury, but officials at the National Earthquake Information Center said some minor damage might be expected.
"At 4.3 it was nothing like the 7.0 that hit Haiti" in January, Earle said. "You're not going to see any structural damage, but there definitely have been a number of people who were shaken."
North Texans confirmed the seismic rumbling.
Parker County Sheriff Larry Fowler said his office received tremor reports from around Brock, and another man reported the walls shaking west of Aledo.
"Our office just shook for 10 seconds or so," said Bobby Johnson of Sacramento Energy Resources in Aledo at 9:16 a.m.
The shaking was "not enough to knock things off the walls," Johnson said, "but it visibly shook pictures and computer monitors and chairs, etc."
Johnson said his office is near the intersection of Old Annetta Road and Farm Road 5 in Aledo.
"We thought it could have been something else because we're pretty close to a freight train, but we didn't see it or hear it coming," Johnson said. "It was something that was just obvious when we realized it."
Johnson is no stranger to aftershocks.
"I used to live in Long Beach, Calif., where I would occasionally feel aftershocks from earthquakes," he said.
Tonya Hicks Williams, who was at her Weatherford home making jewelry, said she could feel the shaking in her body at 9:05 a.m.
"I thought I was crazy until my Chihuahua started barking and running in circles," Williams said.
Her wooden roof started to shake so much, Williams said she thought it was going to collapse.
Williams said that after it stopped, she noticed what she thinks might be some damage to the roof. She said she has called her husband to come home and investigate.
"Now that I know what I felt, it was kind of a cool feeling," Williams said.
Some people in Wichita Falls reported feeling the tremor.
Staffers in the Hardin Administration Building at Midwestern State University said they felt the tremor and local Facebook pages began carrying conversations by people who said they felt it.
North Texans also took to social media to report tremors from the quake. Readers were encouraged to message the Fort Worth Star-Telegram through Facebook and Twitter to report if they felt anything.
-- Brooke Freeman Pettigrew -- "I did, by NAS JRB (Naval Air Station Joint Reserve Base)."
-- Amy Kraul Aguilera -- "I did, in an office off of Trinity and Centreport."
-- Elizabeth Brown Graham -- "Yes. In Keller!"
-- Lauren Potter -- "It also hit Stillwater, OK! (Oklahoma State University). It was the craziest feeling."
-- Vito Munoz -- "We felt it up in Tulsa... 30 seconds of basic movement...Pretty cool from where I'm sitting."
-- Alyssa Yancey -- "Some of us up here at UNT felt it! Very weird!"
-- Morgan Palmer -- "Parents report dogs scared at about that time out in Eastland County."
Heidi Koontz, USGS spokeswoman, said people can report their experiences by going online to earthquake.usgs.gov. From there, click on the link, "Did you feel it?"
Earthquakes are not unheard of in North Texas, Earle said.
"Since 1973," he noted, "you've had three at 4.0 or larger within 100 kilometers of where the earthquake was today near Norman."
Geophysicist Don Blakeman said the earthquake struck at 9:06 a.m. with a preliminary magnitude of 4.5. It was centered about 10 miles northeast of Norman.
Blakeman said the quake was felt as far away as Wichita, Kan.
KGOU in Norman reported that University of Oklahoma officials cordoned off Dale Hall. Students, faculty and staff members were standing outside the campus classroom and office building.
This report contains information from The Associated Press.
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