It was a sharp jolt but also a warning of something much more violent that could be coming. An estimated 9.8 million people felt a magnitude 4.4 earthquake that rumbled across the Bay Area early Thursday, the U.S. Geological Survey reported. It was felt throughout the region, with people more than 150 miles away reporting to the agency that they felt the shaking for perhaps five to 10 seconds. The epicenter of the earthquake is in the area of the Hayward fault,

one of the most feared in the Bay Area, which could produce a magnitude 7 or greater earthquake and is directly underneath heavily populated areas. The Hayward fault, along with the San Andreas fault on the San Francisco Peninsula, have long posed a twin seismic peril to the region. The San Andreas produced the devastating 1989 Loma Prieta quake and 1906 San Francisco quake. READ MORE