San Andreas Fault

Starting near the Salton Sea in southern California and running northward to Mendocino Triple Junction, the San Andreas Fault is a crack in the earth where the Pacific plate meets the North American plate. These plates push against each other as they slide in opposite directions, sometimes causing the ground to give way and create an earthquake.

Fast Facts

1. Location: California
2. Size: Approximately 750 miles long¹
3. Named after Lake San Andreas by California geologist A.C. Lawson
4. Caused the 1906 San Francisco Earthquake
5. 59% chance a major earthquake will hit southern section within 30 years²
6. A 7.8 earthquake in Southern California would cause over 50,000 casualties and do $200 billion in damage³

The Big One

Scientists theorize that the southern section of The San Andreas Fault is likely to cause a large earthquake (7.0+ magnitude on the Richter scale) sometime in the next 30 years.² Although they aren't able to pinpoint exactly when this will occur, they do know that enough stress has accumulated that the fault will move over 18 feet if this stress is released all at once.⁴ Another cause for concern is that the northern and central segments of the fault have each caused a major earthquake within the last 160 years, but the southern segment has not done so in over 300 years.⁴

Quotes

"The southern section of the fault is fully loaded for the next big event."⁵—Yuri Fialko, Scripps Institution of Oceanography

"We are almost certainly not 'overdue' for a repeat of the great 1857 earthquake, but we are clearly well along in the process. We are much too far along, in fact, to neglect serious preparations for the eventuality."⁶—Kerry Sieh, Caltech

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