An earthquake measuring a magnitude of 6.9 on the Richter scale struck the state of Baja California in Mexico today, according to the U.S. Geological Survey, though there have been no reports of damage. The quake was one of a series of four, the strongest of which ocurred 76 miles from Santa Isabel, a town on the peninsula, and was 9.3 miles deep. Authorities are warned to watch out for possible tsunamis and tidal waves.