The Great Earthquake
At 5:12 AM on April 18, 1906, a massive earthquake struck San Francisco with an estimated magnitude of 7.9. The rupture on the San Andreas Fault extended for nearly 300 miles, from San Juan Bautista to Cape Mendocino.
The initial shaking lasted approximately 45-60 seconds and was felt from Oregon to Los Angeles and as far inland as central Nevada. The ground displacement along the fault was as much as 20 feet in some locations.
The Fires
While the earthquake caused significant damage, the subsequent fires proved even more destructive. Broken gas mains and collapsed chimneys ignited fires throughout the city. With water mains also broken, firefighters were largely helpless to stop the blazes.
The fires burned for three days and nights, destroying approximately 25,000 buildings and leaving more than half of San Francisco's 400,000 residents homeless.
Death Toll and Damage
Official estimates at the time placed the death toll at around 700, but modern research suggests the actual number was closer to 3,000. The majority of deaths occurred in San Francisco, but significant casualties were also reported in San Jose, Santa Rosa, and other Bay Area cities.
The total damage was estimated at $524 million in 1906 dollars, equivalent to approximately $16 billion today.
Legacy and Lessons
The 1906 earthquake led to significant advances in earthquake science and building codes. The "Reid's elastic rebound theory," which explains how earthquakes occur, was developed based on observations from this event.
San Francisco rebuilt with improved building standards, and the disaster prompted the development of modern earthquake engineering. The event remains a reminder of the seismic risk facing the Bay Area.