(KRON) — A preliminary 3.1-magnitude earthquake struck on the Concord-Green Valley fault on Friday morning, according to the U.S. Geological Survey. The epicenter was 7.8 miles west of Rio Vista and 8 miles north of Pittsburg. The tremblor occurred at 8:37 a.m., USGS said. Few people reported fee ling it in the area of Fairfield and Vacaville, according to USGS’s “Did You Feel It?” survey. There were no initial reports of damages or injuries. ...read more read less