UPDATE 5:20 p.m.: A magnitude-5.1 quake was centered in Imperial, about 100 miles east of San Diego, at 4:15 p.m. Sunday, according to the U.S. Geological Service.
The quake was centered about 60 miles north of the 6.9 temblor earlier in the afternoon.
UPDATE 4:20 p.m.: Less than a minute after the magnitude 4.1 quake at 2:49 p.m. near Clear Lake, another temblor - magnitude 4 - was reported south of the first epicenter off of Highway 175 near Cobb in Northern California, according to the U.S. Geological Survey.
A magnitude-6.9 earthquake struck at 3:40 p.m. in Baja California, Mexico, rattling much of Southern California, according to the U.S. Geological Survey.
It was centered near Guadalupe Victoria, about 50 miles south of Mexicali, and about 100 miles east of Tijuana and Ensenada, according to the USGS.
The USGS reports moderate shaking in the San Diego area, and mild shaking reported around the Los Angeles and Orange County areas, based on nearly 1,200 reports to the agency's Web site. Some mild shaking was reported as north as Ventura County and Ridgecrest.
Most reports have described the quake as having a long, rolling motion.
About 10 minutes later, a magnitude 4.1-quake was reported centered in Middletown, near Clear Lake between Highway 101 and Interstate 5 in Northern California.View Larger Map