The San Andreas, Living on a Moving Earth

California sits on one of the most active tectonic boundaries on earth. The San Andreas Fault, which runs roughly eight hundred miles from the Salton Sea in the south to Point Arena on the Mendocino coast in the north, is the line where the Pacific Plate and the North American Plate grind past each other at roughly two inches a year. Over millions of years, that movement has carried rocks from what is now near Los Angeles to positions along the northern California coast.

The motion is not smooth. It stores energy in locked sections and releases it in earthquakes. The earthquake of April eighteenth, nineteen oh-six, began at twelve minutes past five in the morning, when a rupture propagated along the San Andreas for nearly three hundred miles from San Juan Bautista to Point Arena.

San Francisco shook for nearly a minute. Gas mains broke. Fires began almost immediately, and burned for three days.

The official death toll was a massive undercount. Modern historians estimate that about three thousand people died, many of them Chinese and Latino residents whose deaths were not recorded in official tallies. Approximately four hundred ninety city blocks burned.

The nineteen eighty-nine Loma Prieta earthquake, which struck during the third game of the World Series and was broadcast live on national television, collapsed the Cypress Structure freeway in Oakland, killing forty-two people, and brought down a section of the Bay Bridge. The nineteen ninety-four Northridge earthquake under the San Fernando Valley caused more than forty billion dollars in damage, the costliest American earthquake on record at that time. Californians have learned to build for earthquakes.

Seismic retrofits, base isolators, flexible utility connections. They have not learned to avoid them, because there is nowhere in California to go that is truly away from the fault.