The U.S. Geological Survey said the temblor occurred at 5:28 a.m. PST at a depth of 3.7 miles.
The epicenter was 22 miles from Paso Robles and 124 miles from San Jose City Hall, the Los Angeles Times reported.
There were no reports of injuries or damage.
Hearst Castle, the former mansion of newspaper magnate William Randolph Hearst, is a U.S. National and California Historical Landmark.
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