active fault in the earth's crust extending northwest from S California for about 600 miles (966 km)
after San Andreas valley, through which the fault runs: orig. Sp, San Andrés, St. Andrew
See San Andreas fault in American Heritage Dictionary 4
A major zone of fractures in the earth's crust extending along the coastline of California from the northwest part of the state to the Gulf of California. Movement of the tectonic plates along the fault has caused numerous tremors, including the devastating San Francisco earthquake of 1906.