'Robust Sequence' of Earthquakes Shake Eastern California
Fox News (Link) - AP (October 2, 2009)
Earthquakes up to magnitude 5.2 struck Friday evening in a remote area of eastern California that was been shaken by a sequence of temblors a day earlier.
Inyo County sheriff's dispatcher Carol Drew said no damage or injuries were reported, but the department received several calls about the quakes.
The quakes' epicenters were just southeast of the town of Lone Pine in the arid Owens Valley below the eastern slope of the Sierra Nevada, about 180 miles north of Los Angeles.
"It's a very robust sequence," said California Institute of Technology seismologist Anthony Guarino.
The 5.2 quake occurred at 6:15 p.m. at a very shallow depth and was preceded by tremors of 4.7 and 4.9 in a six-minute span, the U.S. Geological Survey said.
Guarino said most California quakes are six to 10 miles deep, but the biggest quake was centered less than a kilometer beneath the earth's surface, according to the U.S. Geological Survey's measurements.
This means more intense shaking felt over a wider area and maybe even a visible crack in the ground, he said.
The sequence was followed by more than a dozen smaller quakes including three in the magnitude-4 range.
About 3 a.m. Thursday, a magnitude-5 earthquake occurred in the same area. Dozens of mostly tiny aftershocks have followed. A magnitude 5 quake is capable of causing considerable damage.
Guarino said the tremors were likely on a strike-slip fault, with two blocks of earth sliding past each other.
The Owens Valley is a long, narrow valley lying between the towering peaks of the Sierra that rise abruptly on the west and the Inyo Mountains on the east. It is sparsely populated except for string small cities and towns along U.S. 395, a major route between Southern California and Sierra destinations.
In 1872, the town of Lone Pine was leveled by an earthquake which measured about magnitude 7.6 and was felt as far away as San Diego.
Naturalist John Muir was in Yosemite Valley at the time and wrote about seeing huge pieces of granite crashing down the mountains into talus piles beneath steep hillsides.
Lone Pine currently has 1,600 residents.