An earthquake with a preliminary estimated magnitude of 4.5 struck northern Baja California today, and was felt through much of San Diego County, but no damage was immediately reported.
The epicenter of the shaker, which struck at 1:35 p.m., was 21 miles south of Tecate, or 40 miles southeast of downtown San Diego, according to the U.S. Geological Survey.
Police and fire officials in El Cajon, Kearny Mesa and Escondido reported feeling the earthquake, but said they received no emergency calls.
Other officials in downtown San Diego and National City reported that they didn't feel it.
Shakemap projections from the USGS indicated that very light damage could be expected near the epicenter, although moderate shaking would be expected to be felt there. The shakemap technology uses scientific knowledge about land characteristics in specific locations to calculate shaking.
A 3.0 aftershock was measured at 1:40 p.m., followed by a 2.1 shock at 1:51, and a 2.4 shock at 2:10.
The temblors were shallow -- about a half mile deep -- according to preliminary data from USGS seismographs north of the border. Exact information about quakes in Baja Califrornia sometimes is revised, after seismologists examine data from sensors north of the border.
The epicenter for the quakes was estimated to be in the Santo Tomas Valley, a vineyard area along Federal Highway 3 between Tecate and Ensenada. Tecate is a pair of border towns, home to a large brewery, about 30 miles east of San Ysidro.
Today's quakes were centered about 45 miles southwest from Saturday's 3.4 earthquake, on the San Diego-Imperial County line near Ocotillo.
