CHINO HILLS, California: Despite shaking a large swath of Southern California, a magnitude 5.4 earthquake was not the "Big One" that scientists have long feared. Still, it rattled nerves, causing people to vow to step up their emergency preparations. The quake, which was felt Tuesday from Los Angeles to San Diego, caused only limited damage and minor injuries, and served as a reminder of the seismic danger below sprawling freeways and housing developments. The epicenter was just outside Chino Hills, about 30 miles, or 50 kilometers, southeast of the center of Los Angeles. Dozens of aftershocks followed. "We were really fortunate this time," said Captain Jeremy Ault of the Chino Valley Independent Fire District. "It's a good opportunity to remember that we live in earthquake country. This is part of living in Southern California and we need to make sure we're prepared." To prepare for the "Big One," scientists and emergency planners will hold in the fall what is described as the largest earthquake drill in the United States. It will be based on a hypothetical magnitude 7.8 earthquake.