The 1906 San Francisco Earthquake

At 5:12 a.m. on April 18, 1906, the San Andreas Fault ruptured along about 477 kilometers of the northern California coast, and San Francisco, then the largest city on the West Coast, shook for under a minute. The shaking toppled chimneys, split water mains and broke gas lines, and the fires that followed did most of the damage. For three days they burned across downtown, the waterfront and much of the city, destroying about 28,000 buildings. More than half of the city's roughly 400,000 residents were left homeless. The disaster also gave geologists their clearest look yet at how faults store and release strain, an idea that still underpins earthquake science.

The epicenter lay just offshore near Mussel Rock, about 3 kilometers west of San Francisco, and the rupture tore both north toward Cape Mendocino and south toward San Juan Bautista. Its magnitude is estimated at about 7.9. Along the fault, fences, roads and rows of trees were offset by as much as 6 meters, most strikingly in Marin County near Point Reyes and Tomales Bay. Within the city the worst damage struck filled land along the bay shore and the South of Market district, where loose soils amplified the shaking. Santa Rosa, San Jose and Stanford University also suffered heavy losses. The fires, fed by broken gas mains and spread by misjudged dynamiting, ran unchecked because the quake had cut the water supply, and were finally stopped along Van Ness Avenue.

Officials at the time reported 375 to about 500 deaths, a figure later historians consider a large undercount, partly because deaths in Chinatown and among transient workers went unrecorded. Research by the city archivist Gladys Hansen raised the estimate to about 3,000, the figure most often cited today. A state commission led by the geologist Andrew Lawson published a landmark report in 1908, and from its survey data Harry Fielding Reid developed the elastic-rebound theory, which explains earthquakes as the sudden release of strain built up across a fault. The city rebuilt quickly and hosted the Panama-Pacific International Exposition in 1915. Today the San Andreas is among the most closely studied faults on Earth, and seismologists expect a comparable rupture to occur again.

• The 2023 Turkey–Syria Earthquakes
  Twin magnitude 7.8 and 7.5 shocks on the East Anatolian Fault that killed nearly 60,000 people in southern Turkey and northern Syria another great strike-slip rupture
• Pacific Ocean
  Earth's largest and deepest ocean epicenter just off
• United States
  A continental superpower of fifty states and astonishing variety located in
• The Ring of Fire
  The Pacific rim of subduction, where the ground does not hold still on the edge of
• The Tectonic Plates
  The seven great slabs and dozens of smaller ones that make up Earth's moving shell Pacific–North American plate boundary
• The San Andreas Fault
  California's 1,200-kilometer seam between the Pacific and North American plates ruptured
• San Francisco
  California's hilly bay city, capital of the tech economy struck