An earthquake with a preliminary magnitude of 4.3 struck 16.2 miles southwest of Lompoc in Santa Barbara County on Thursday, the U.S. Geological Survey said.

The temblor, which struck at 1:38 p.m. PT, was centered 20.5 miles south-southwest of Vandenberg Air Force Base and 82 miles west of Ventura.

The quake was initially measured as having a magnitude of 4.6 before it was downgraded.

Residents in Ventura, Oxnard, Oak View and Port Hueneme felt shaking from the temblor.

There were no immediate reports of damage or injuries.