Posted: March 20, 2006    The Earth's crust is broken up into plates that move slowly, causing a buildup of pressure in certain areas that rupture when the pressure becomes too great. These breaks in the Earth's surface, or faults, are where earthquakes occur. The San Francisco Bay area is home to seven major fault lines, the largest being the San Andreas Fault which stretches for 800 miles along the California coast. For each fault, scientists assigned a percentage of probability for when a major earthquake -- of magnitude 6.7 or greater -- might occur. Click on each fault to get more information.		Main: The 1906 Earthquake Birth of Earthquake Science Bay Area Preparedness P-wave Warnings Map: Major Bay Area Faults Slide Show: Deconstructing the 1906 Quake Interactive: Will This Building Stand? Lesson Plan: History Through First-Person Accounts