FREMONT (CBS SF) -- Three aftershocks rattled the Fremont area overnight after a 4.0 earthquake struck Tuesday morning.
The largest aftershock, a 2.1-magnitude, hit at 11:39 p.m. Tuesday night, following by a 1.3-magnitude and a 1.4-magnitude several hours later.
Smaller aftershocks tend to strike within the main earthquake rupture on parts of the fault that did not break during the original earthquake.
Tuesday's early morning quake was centered about 1.5 miles NNE of Fremont and occurred at 2:41 a.m.
While there were no reports of serious damage, the KPIX newsroom received calls from Santa Clara, San Francisco, Pleasanton, and San Ramon from people reporting the earthquake.
The fault that produced Tuesday's earthquake is expected to produce a major earthquake "any day now," according to a U.S. Geological Survey scientist.
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