Colorado shaken by largest earthquake quake since 1973

Tuesday, August 23, 2011 | 8:42 a.m. CDT; updated 10:44 a.m. CDT, Tuesday, August 23, 2011

DENVER — The largest earthquake to strike Colorado in almost 40 years has shaken hundreds of people near the New Mexico border and caused minor damage to a few homes.

The magnitude 5.3 earthquake was recorded at about 11:46 p.m. MDT Monday about nine miles southwest of Trinidad, Colo., and about 180 miles south of Denver, according to the National Earthquake Information Center in Golden, Colo. The quake followed three smaller ones that hit the area earlier in the day.

The quake is the largest in Colorado since a magnitude 5.7 was recorded in 1973, U.S. Geological Service geophysicist Amy Vaughn said. That one was centered in the northwestern part of the state — about 50 miles north of Grand Junction, she said.

USGS geophysicist Jessica Sigala said Tuesday the earthquake damaged chimneys, cracked walls and knocked items off shelves, but there were no injuries.

A few homes have been damaged, and there were rockslides on Colorado Highway 12 and Interstate 25, but both highways remained open, a Las Animas County Sheriff's Office dispatcher said Tuesday.

The dispatcher, who would only give her first name as Kristina, said she was working when the biggest earthquake hit near midnight.

"Everything was shaking, but we had no power loss," she said.

She said authorities were still trying to assess the damage.

"I thought maybe a car had hit my house," 70-year-old Trinidad resident Nadine Baca said. "Then I called to my son, and he said it was the third (quake) today."

Another USGS geophysicist, Shengzao Chen, said the information center had received calls from more than 70 people in Trinidad and several dozen people in New Mexico who felt the shaking. More than 30 people in Colorado Springs, about 130 miles north of Trinidad, also reported feeling the quake, he said.

Sigala said there were several minor earthquakes that preceded the bigger one, including a magnitude 2.9 earthquake recorded about 8 a.m. Monday. A 4.6 quake was felt in the same area at 5:30 p.m., and a magnitude 3.0 quake was recorded about 9 p.m. There have been four aftershocks.

Sigala said the area occasionally has swarms of earthquakes, some lasting days or weeks, but Monday's temblor was unusual.

"A 5.3 is big for Colorado," she said.

The last time the area received such a series of earthquakes was in August and September 2001, when about a dozen smaller-sized temblors were recorded, Sigala said.

She said some people blamed that swarm on oil drilling in the area, but she said later studies proved those fears unfounded. 

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Ellis Smith August 24, 2011 | 7:23 a.m.

(1)The Raton (literally Spanish for "rat") Mountains are an interesting geologic formation, running to the east and at right angles from the main Sangre de Cristo ("blood of Christ") Mountains for about 100 miles before sinking into the Great Plains. The range drops off sharply on the New Mexico (south) side into a plain which contains some extinct volcanoes, including Capulin National Monument, an extinct volcanic cone that can be climbed by the public using a man-made serpentine trail.

The area is sparsely populated, with Trinidad ("Trinity"), Colorado and Raton, New Mexico being the only small cities. I-25 crosses it at Raton going north and south.

(2) The National Earthquake Information Center is located at Golden, Colorado on the campus of Colorado School of Mines.

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