Quake activity along the San Andreas fault is picking up

Oklahoma quake is largest in state history

A record 5.6 magnitude earthquake shook Oklahoma on Saturday night, less than 24 hours after a 4.7 temblor hit the state, authorities said.

Early reports indicate that there was no major damage.

The earthquake was centered about 45 miles northeast of Oklahoma City, in roughly the same area of Lincoln County as the initial quake that occurred at 2:12 a.m.

The latest quake, which happened at 10:53 p.m., Central Time, sent shock waves for about 20 to 30 seconds, authorities said. It was part of a series of quakes Saturday.

Survey officials said the earthquake was at a depth of 3.1 kilometers and most likely occurred on theWilzetta fault, also known as the Seminole uplift.

According to the Oklahoma Geological Survey, the second-strongest earthquake in state history was a 5.5 magnitude quake near El Reno in 1952.

The earlier 4.7-magnitude earthquake had rattled the region at 2:12 a.m. Saturday and was felt as far away as Arkansas, Kansas, Missouri and Texas.

Nov. 6, 2011 11:37 AM ET
USGS: 10 aftershocks following 5.6 quake in Okla.

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.

It was followed by 10 aftershocks by midmorning Sunday. But although homes and other buildings cracked and suffered minor damage, there were no reports of severe injuries or major devastation.

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 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 aftershocks included two that were magnitude 4.0, one about 4 a.m. Sunday and one about 9 a.m., USGS said. The smallest aftershock it recorded was magnitude 2.7. USGS seismologist Paul Earle in Golden, Colo., said the aftershocks will likely continue for several days and could continue for months.

Oklahoma typically has about 50 earthquakes a year, and 57 tornadoes, but a burst of quakes east of Oklahoma City has contributed to a sharp increase. Researchers said 1,047 quakes shook Oklahoma last year, prompting them to install seismographs in the area. The reason for the increase isn't known, and Turner said there was no immediate explanation for the weekend spurt in seismic activity.

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.

"We definitely felt it," Collins said. "I was at home, getting ready for bed and it felt like the house was going to collapse. I tried to get back to my kids' room and it was tough to keep my balance, I could hardly walk."

Jesse Richards, 50, of Sparks, said his wife ran outside when the shaking started because she thought their home was going to collapse. One of her cookie jars fell on the floor and shattered, and pictures hanging in their living room were knocked askew. He estimated the big earthquake lasted for 45 seconds to a minute.

"We've been here 18 years, and it's getting to be a regular occurrence," Richards said. But, he added, "I hope I never get used to them."

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. Other reports Sunday were sketchy and mentioned cracks in some buildings and a chimney toppled.

"Earthquake damage in Oklahoma. That's an anomaly right there," Todd McKinsey of Moore told The Oklahoman newspaper after the magnitude 5.6 earthquake centered 50 miles away left him with cracked drywall. Most earthquakes that have hit the region have been much smaller.

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 4.0 magnitude 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."

Plumb said she was anxious because of the number of earthquakes in so short a span and the fact that they were so strong.

Saturday's late-night quake was slightly less in intensity than the one that rattled the East Coast on Aug. 23. That 5.8 magnitude earthquake was centered in Virginia and felt from Georgia to Canada. No major damage was reported, although cracks appeared in the Washington Monument, the National Cathedral suffered costly damage to elaborately sculpted stonework, and a number of federal buildings were evacuated.

Oklahoma has had big earthquakes before. USGS records show a 5.5 magnitude earthquake struck El Reno, just west of Oklahoma City, in 1952 and, before Oklahoma became a state in 1907, a quake of similar magnitude 5.5 struck in northeastern Indian Territory in 1882.

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.

Mexico City Shaken by Magnitude-6.5 Quake
By Nacha Cattan and Ben Bain - Dec 11, 2011

A magnitude 6.5 earthquake centered in the southern Mexican state of Guerrero shook the capital of Latin America’s second-biggest economy. Two people were killed in Guerrero, the country’s civil protection agency said.

The quake occurred at 7:47 p.m. local time and was centered 166 kilometers (103 miles) southwest of Mexico City, according to the U.S. Geological Survey.

“All services in Mexico City are functioning normally,” Mexican President Felipe Calderon said via the Twitter website at approximately 10 p.m. An 18-year old was killed in Iguala, Guerrero, when a restaurant roof collapsed, and a 25-year old was killed on the Chilpancingo-Acapulco highway, the civil protection agency said in an e-mailed statement.

Petroleos Mexicanos, the state-controlled oil company known as Pemex, said its infrastructure wasn’t damaged. Mexico City Mayor Marcelo Ebrard said on Twitter that the capital’s airport, subway and the water systems are functioning normally.

The temblor left 30 neighborhoods in Mexico City without power, the Excelsior newspaper reported, citing the federal electricity commission. Police chief Manuel Mondragon y Kalb said in an interview with Foro TV two buildings in the city were reported to be damaged, including one that was leaning on another structure. He confirmed power outages in some parts of the city.

December 10, 2011 9:55 PM

Strong quake shakes from Mexico City to Acapulco
(AP)

MEXICO CITY - A 6.5-magnitude earthquake struck in Mexico's western Guerrero state Saturday night, shaking buildings and causing panic in the nation's capital and the Pacific resort of Acapulco. Officials said at least three people died, but there were no reports of widespread damage.

The U.S. Geological Service initially estimated the quake at magnitude at 6.8, but downgraded it to 6.7 and then 6.5. A quake of that magnitude is capable of causing severe damage, although the depth of this temblor lessened its impact.

The USGS said the quake occurred at a depth of 40.3 miles (64.9 kilometers). It was centered about 26 miles (42 kilometers) southwest of Iguala in Guerrero and 103 miles (166 kilometers) south-southwest of Mexico City.

Mexico's Interior Department said the quake was felt in parts of nine states.

Humberto Calvo, undersecretary of Guerrero's Civil Protection agency, said three deaths had been reported in the state. He said one man was killed when a house's roof collapsed in Iguala, a second died in the small town of Ixcateopan and the driver of a cargo truck was killed by rocks that fell on the vehicle driving on the toll highway linking Acapulco with Mexico City.

Calvo said a secondary highway between the two cities was blocked in two places by rockslides.

High-rises swayed in the center of Mexico City for more than a minute, and shoppers were temporarily herded out of some shopping centers until the danger passed.

Mexico City's mayor, Marcelo Ebrard, reported by Twitter that no major damage had been reported. He said power failed in some parts of the city.

People in one part of Mexico City's upscale Condesa neighborhood ran out of their houses and gathered in the streets, hugging each other while some shook and began to cry.

On one street, a group of women joined hands in a circle, closed their eyes and began to pray.

"Please God, help us and let everything be OK," said one. "It's OK. It's OK. Everything is OK."

Parts of Mexico City rest on the shaky soil of a former lake bed, which tends to magnify the effect of earthquakes. An 8.1-magnitude quake in 1985 killed as many as 10,000 people in the city.

In Acapulco, which is in Guerrero, hundreds of anxious tourists congregated in the street after fleeing rocking buildings that are strung along the coastal boulevard. Patrons also left a movie theater complex.

Authorities said they found no structural damage and had no reports of injuries in the Pacific resort, which was about 87 miles (140 kilometers) from the quake's epicenter.

Rogelio Trujillo, chief of security at a Soriana department store in Acapulco, said perfume bottles, groceries and paintings had been shaken off shelves and customers ran out.

Alberto Orbe, a radio operator for the city's Civil Protection agency, said the office had received many phone calls from panicked residents.