MENLO PARK, Calif., Sept. 30 (UPI) -- An earthquake of magnitude 5.0 hit central California on Thursday, the fourth such quake in three days, the U.S. Geological Survey reported.
The quake hit at 11:54 a.m. Pacific time, about 11 miles west-northwest of Parkfield, the site of the first quake -- a magnitude 6.0 event -- Tuesday. No damage or injuries were reported.
Wednesday, two minor quakes hit the same general vicinity, according to the USGS national earthquake data center. Those quakes, which registered, respectively, 4.5 and 5.0 on the Richter scale, followed by a day the 6.0 quake that Parkfield and was felt from San Francisco to Los Angeles.
The Richter scale, which has been in use since 1935, can predict general earthquake effects, with events of magnitude 5.4 and under generally felt but rarely causing damage. The scale has no maximum, but quakes of magnitudes above 8 -- which can cause tremendous damage -- are rare.
