Two moderate earthquakes—100 miles and 14 hours apart—this week near opposite ends of the Calaveras Fault were reminders of the 30th anniversary on Oct. 17 of the 1989 Loma Prieta earthquake.
A 4.7-magnitude tremor along the Calaveras Fault near Tres Pinos rattled shelves in Hollister and Gilroy at 12:42pm Oct. 15, according to the U.S. Geological Survey. At least three small aftershocks were reported from the quake, which was felt from San Jose to San Luis Obispo, and from Monterey to Los Banos,
The Tres Pinos quake occurred about 14 hours after a 4.5 earthquake was recorded near the northern end of the Calaveras Fault, at Pleasant Hill, in Contra Costa County. That quake also was felt over a wide area of more than 15 counties, and spawned more than a dozen small aftershocks.
There were no reports of damage or injuries from either quake. Trains were delayed on Monday night due to the inspection of the tracks after the Pleasant Hill quake. The USGS identified that quake as a result of the movement of an unmapped fault situated between Concord and Calaveras faults in the East Bay.
