Preliminary magnitude 3.9 earthquake strikes near San Ramon, followed by aftershocks, USGS says
SAN RAMON, Calif. -- An earthquake with a preliminary magnitude of 3.9 struck southeast of San Ramon at 6:31 p.m. Saturday, the U.S. Geological Survey said.
USGS said the tremor, revised down from a preliminary reading of 4.0, was about 9.6 km in depth.
Aftershocks followed, with USGS reporting a preliminary magnitude 2.8 at 6:36 p.m. and a 3.0 at 6:53 p.m.
This happened just one day after a cluster of at least nine earthquakes struck the area on Friday night. The largest magnitudes were recorded at 4.0 and 3.8.
RELATED: San Ramon rattled by several quakes, ranging from 2.5 to 4.0 in magnitude
According to the Geological Survey, people typically report feeling earthquakes larger than about magnitude 2.5.
The closer to the surface an earthquake occurs, the more ground shaking and potential damage it will cause.
Scientists say an earthquake measuring 4.0 on the open-ended Richter magnitude scale is considered a light to moderate event.
While it's strong enough cause noticeable shaking, it rarely causes significant structural damage.
No injuries have been reported.
Bay City News contributed to this report.
MAP: Significant San Francisco Bay Area fault lines and strong earthquakes
Zoom in on the map below and compare where you live to the significant faults and where strong earthquakes have struck in the Bay Area.
Stay with ABC7 News for the latest details on this developing story.
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