USGS retracts report of strong NorCal quakes

April 5, 2010 6:41:51 AM PDT
Seismologists have retracted reports of two magnitude-4 earthquakes that struck near the Geysers on Sunday, saying the quakes were in fact insignificantly small, according to a spokesman with the U.S. Geological Survey.

The earthquakes struck at about 3:50 p.m. within minutes of each other. They were centered about three miles east of the Geysers and 14 miles east of Cloverdale, according to the USGS.

The quakes were triggered by a 7.2-magnitude quake in Mexico and Southern California, and they initially registered as magnitudes 4.0 and 4.1, the USGS spokesman said.

However, the larger quake caused automated software to miscompute the smaller quakes, according to spokesman David Oppenheimer.

The software was actually measuring the amplitude of the Baja California quake, he said. The quakes near the Geysers were really about magnitude-1.5, which is considered insignificant.

Oppenheimer said the miscalculation was not unusual, and analysts will compute the precise magnitudes of the Geyser quakes later today.

The quakes were removed from the U.S. Geological Survey's Web site because they were so small, Oppenheimer said.


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