A magnitude 4.9-magnitude aftershock to last Friday’s 7.1 earthquake hit the Ridgecrest area of Kern County today, the U.S. Geological survey reported.

It struck at 6:11 a.m. at a depth of 5.5 miles, its epicenter 4.8 miles east-northeast of Ridgecrest.

The temblor is believed to have been the biggest aftershock recorded in the region. There have been hundreds of them, but none greater than 3.9.

The 4.9 report was based on a seismologist’s finding, not a computer- generated report.

The Los Angeles Fire Department reported after the aftershock that it is in “earthquake emergency mode” with fire department vehicles and helicopters patrolling the department’s jurisdiction to identify any damage or emergency needs, said fire department spokeswoman Margaret Stewart.