The strongest earthquake to shake Colorado in forty years has rattled the southern part of the state near the New Mexico border. The series of quakes yesterday, capped by the 5.3 quake at 11:46 last night, were centered south of Cokedale in Las Animas County. Aftershocks were still being felt early this morning. The quake caused minor damage and rockslides in the area.

The quake at 11:46 p.m. Monday was the largest in Colorado since a magnitude 5.7 was recorded in 1973, said USGS geophysicist Amy Vaughn. That one was centered in the northwestern part of the state — about 50 miles north of Grand Junction, she 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.

Rockslides were reported on Colorado Highway 12 and Interstate 25, but both highways remain open.