The Great San Francisco Earthquake & Fires of 1906
A City Trembles
At 5 a.m. rocks snapped below the surface of the earth and land was torn asunder for nearly 200 miles between the cities of San Juan Bautista and Point Arena in California. The epicenter was on the San Andreas Fault at the boundary of San Francisco and San Mateo counties. The earthquake was not the strongest ever experienced in California, but it was the closest to a populated urban center. Its intensity was felt throughout most of California and extended to parts of Nevada and Oregon.
The seismic waves spread outward. Ship captains thought they had collided with rocks. City streets heaved up and down as if subjected to ocean swells. The damage was immediate and most severe on the land–fill. The crowded, four–story Valencia Street Hotel shrank to one story, trapping most of its occupants. The landmark San Francisco City Hall, a recently completed $7 million and ten–year construction extravaganza, was crushed in the earthquake shaking. Ft. Bragg and Santa Rosa were badly damaged, as was San Jose and Stanford University to the south.
Vulnerable Building Practices
Much of San Francisco was built on three unstable surfaces: steep hillsides, rolling sand dunes, and former marshes. During the 1906 earthquake, structures on made land or infill, suffered the most damage because this land was so unstable and unsettled. In 1906, a number of major pipeline breaks occurred in the city of San Francisco during the earthquake because of lateral spreading. Water main breaks hampered efforts to fight the fires that ignited during the earthquake. Thus, rather inconspicuous ground-failure displacements of less than seven feet were largely responsible for the devastation to San Francisco in 1906.
Before the earthquake, the Valencia Street Hotel was an extreme example of the danger of liquefaction to residents living on made land. When the quake struck, patrons in a coffee shop on the bottom floor of the hotel ran from the building in time to watch the building simultaneously lurch forward and sink, making the hotel's fourth floor the hotel's only floor above ground causing nearly 100 deaths.