1906 San Francisco Earthquake and Fire

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Key Takeaways

• The 1906 San Francisco earthquake struck at 5:12 AM on April 18, 1906, with a magnitude of M7.9, rupturing 477 km of the northern San Andreas Fault.
• Approximately 3,000 people died and more than 80% of San Francisco was destroyed — most of the damage caused not by shaking but by three days of uncontrollable fires.
• Broken water mains left firefighters helpless, and misguided dynamiting by the military spread fires rather than containing them.
• Of San Francisco's 400,000 residents, roughly 225,000 were left homeless, creating one of America's largest refugee crises.
• The disaster produced foundational advances in earthquake science, including Harry Fielding Reid's elastic rebound theory and Andrew Lawson's comprehensive fault mapping.
• City leaders deliberately downplayed the earthquake's role and blamed the fires to protect real estate values — a cover-up that delayed seismic safety reforms for decades.

Introduction

At 5:12 AM on Wednesday, April 18, 1906, the northern segment of the San Andreas Fault ruptured along 477 kilometers of California coastline. The resulting M7.9 earthquake shook San Francisco for 45 to 60 seconds, toppling buildings, snapping gas lines, and shattering the city's water infrastructure. But the shaking was only the beginning. Over the next three days, fires — fed by ruptured gas mains and fanned by shifting winds — consumed more than 80% of San Francisco's built environment.

The 1906 San Francisco earthquake remains one of the deadliest and most consequential natural disasters in American history. Approximately 3,000 people perished. Some 225,000 of the city's 400,000 residents were left homeless. The total property loss, estimated at $400 million in 1906 dollars (roughly $13 billion today), made it the costliest disaster the United States had ever experienced at that time.

But the earthquake's legacy extends far beyond destruction. The scientific investigations that followed fundamentally changed how humans understand earthquakes. The political response — a deliberate campaign to minimize the earthquake's role and blame the fires — shaped San Francisco's relationship with seismic risk for generations. And the rebuilding effort, completed with remarkable speed, became a model for urban disaster recovery.

This article examines the 1906 San Francisco earthquake in full: the geology, the shaking, the fires, the human toll, the science, and the cover-up.

San Andreas Fault What Causes Earthquakes

The Geology: A Fault Under Pressure

The San Andreas Fault is a transform boundary where the Pacific Plate slides northwestward past the North American Plate at a rate of approximately 50 mm per year. This motion is not smooth — the plates lock against each other, accumulating strain energy over decades or centuries, then releasing it suddenly in earthquakes.

By 1906, the northern San Andreas had been locked for an estimated 150 years or more. The last major rupture on this segment likely occurred around 1838, and possibly as far back as 1690. Strain had been accumulating at the full plate motion rate, storing enormous elastic energy in the crust on either side of the fault.

When the fault finally ruptured on April 18, it broke along approximately 477 km — from San Juan Bautista in the south to Cape Mendocino in the north. The rupture propagated in both directions from an epicenter located offshore, approximately 3 km west of San Francisco near Mussel Rock. Maximum horizontal displacement reached 6.1 meters (20 feet) near the town of Olema in Marin County, where a fence line was offset dramatically — a photograph that became one of the most iconic images in earthquake science.

The earthquake's magnitude has been estimated at M7.9 by the USGS, based on modern reanalysis of seismograms and field observations. Some earlier estimates placed it as high as M8.3, but current consensus centers on M7.9.

Learn more about the San Andreas Fault

The Earthquake: 45 Seconds That Changed a City

The Shaking

San Franciscans were jolted awake at 5:12 AM by violent shaking that lasted between 45 and 60 seconds. The earthquake arrived in two distinct phases: a sharp initial jolt, followed by a brief pause of approximately 10 seconds, then a much stronger and longer period of intense shaking.

The ground motion was devastating for the city's built environment. San Francisco in 1906 was a densely built city of wood-frame Victorian houses, unreinforced brick commercial buildings, and a handful of newer steel-frame structures. The wood-frame buildings generally performed well during the shaking itself — their flexibility allowed them to absorb seismic energy. But unreinforced masonry buildings fared terribly. Brick facades collapsed into the streets, chimneys toppled through roofs, and entire walls sheared away from buildings.

The most catastrophic structural failure was at the Valencia Street Hotel in the Mission District, a four-story wooden building constructed on filled marshland. The building sank three stories into liquefied ground, trapping and killing an estimated 100 or more occupants. Rescuers pulled survivors from the upper-story windows, which were now at street level.

City Hall, an ornate building that had taken 27 years and $6 million to construct, was gutted in seconds. Its steel frame survived, but the unreinforced masonry walls and the elaborate dome collapsed, later revealing shoddy construction practices — the walls had been filled with rubble and newspaper instead of proper mortar, the product of decades of corrupt contracting.

Immediate Aftermath

Within minutes of the shaking, fires began breaking out across the city. Ruptured gas lines ignited in dozens of locations. Overturned stoves and broken chimneys started fires in homes. By 6:00 AM, more than 50 separate fires were burning.

San Francisco Fire Chief Dennis Sullivan, the one man who had spent years planning for exactly this scenario, was mortally wounded when a falling chimney crashed through the roof of the fire station where he slept. He died three days later without regaining consciousness. His death left the fire department without its most experienced leader at the worst possible moment.

The Fire: Three Days of Destruction

Day 1 — April 18: The Fires Merge

The fire department responded immediately but discovered within minutes that the city's water system had been destroyed. The earthquake had broken the main water conduits from Crystal Springs and San Andreas reservoirs in the Peninsula — ironically, the reservoirs sat directly on the San Andreas Fault. In the city itself, hundreds of smaller water mains had fractured. When firefighters connected hoses to hydrants, nothing came out.

Without water, the firefighters were nearly helpless. They attempted to create firebreaks by demolishing buildings in the fire's path, but they had limited dynamite and no experience with controlled demolition. Meanwhile, the fires merged into massive conflagrations. The "Ham and Eggs Fire," started when a woman at 395 Hayes Street lit her stove to cook breakfast, unaware that her chimney had been cracked by the earthquake. This fire grew to become one of the largest, eventually consuming Hayes Valley, the Civic Center, and much of the Western Addition.

By noon on April 18, Brigadier General Frederick Funston had ordered U.S. Army troops from the Presidio into the city. Funston, acting without authorization from Washington, declared martial law (though it was never formally enacted by the president or governor). Soldiers began dynamiting buildings to create firebreaks — a strategy that frequently backfired. The troops used black powder and crude explosives rather than proper demolition charges, and the blasts often scattered burning debris, starting new fires. In several documented cases, dynamiting directly caused fires to spread into neighborhoods that might otherwise have been spared.

Day 2 — April 19: The Firestorm Peaks

By the second day, the fires had merged into a single massive firestorm covering the heart of the city. Temperatures in the fire zone exceeded 1,500°F (815°C). The heat was so intense that steel rails twisted and granite building stones crumbled. The firestorm created its own wind system, generating powerful updrafts that pulled in air from surrounding areas, feeding the flames.

The fire moved through Chinatown, destroying the densely populated neighborhood completely. It advanced up Nob Hill, consuming the mansions of the city's wealthiest residents — the Flood, Hopkins, Stanford, and Crocker estates. Only the Fairmont Hotel's exterior walls survived, though the interior was gutted.

The greatest stand against the fire occurred along Van Ness Avenue, the city's widest street at 125 feet across. Soldiers and firefighters deliberately dynamited and burned buildings along the east side of Van Ness to create a massive firebreak. Using water pumped from the bay through a fireboat and a long hose relay, they were able to hold the western line. This saved the Western Addition and the entire western half of the city.

Day 3 — April 20: The Fires Die

Rain began falling on the evening of April 20, helping to extinguish the remaining fires. By April 21, the fires were effectively out, though some areas smoldered for days.

The destruction was staggering. Over 28,000 buildings had been destroyed. The burned area covered approximately 4.7 square miles (12.2 km²) — more than 80% of the city's built environment. Nearly every building south of Market Street and east of Van Ness Avenue was gone.

Timeline of the Earthquake and Fire

The Human Toll

Deaths and Injuries

For decades, the official death toll stood at 478 — a number produced by the city's post-disaster government and clearly a gross undercount. Modern research by Gladys Hansen, San Francisco's city archivist, documented at least 3,000 deaths through painstaking analysis of death certificates, coroner's records, and other primary sources. Many researchers believe the true number may be higher, as deaths in Chinatown and among undocumented residents were systematically undercounted.

The causes of death varied. Some were killed instantly by collapsing buildings during the earthquake. Others were trapped in rubble and died in the subsequent fires. An unknown number were shot by soldiers or vigilantes enforcing the military's "shoot-to-kill" orders against looters — orders that were of dubious legality and applied disproportionately against minorities and the poor.

Refugees and Displacement

Of San Francisco's estimated 400,000 residents, approximately 225,000 — more than half the population — were left homeless. The displaced population fled to Golden Gate Park, the Presidio, and open spaces throughout the city. Within days, the Army established formal refugee camps, eventually housing more than 20,000 people in tents and later in small wooden "earthquake cottages."

The refugee camps operated under strict military discipline. Cooking was prohibited inside tents due to fire risk. Communal kitchens served meals. Sanitation was managed through organized latrine systems. Despite the regimentation, the camps were remarkably effective at preventing the epidemics that typically followed urban disasters — there was no major outbreak of disease.

The city's Chinese community faced particular hardship. Chinatown had been completely destroyed, and city leaders initially attempted to relocate the Chinese population to an isolated area at Hunters Point, far from the valuable real estate that Chinatown occupied. This plan was ultimately defeated by Chinese community leaders and the intervention of the Chinese government, which threatened trade repercussions.

Damage Statistics

The Rebuilding

San Francisco's rebuilding was remarkably rapid. Within three years, more than 20,000 buildings had been constructed. By 1915, the city hosted the Panama-Pacific International Exposition, presenting itself to the world as a fully recovered, modern metropolis.

However, the rebuilding largely replicated the pre-earthquake city's vulnerabilities. Despite proposals from architect Daniel Burnham for a comprehensive redesign with wider streets and more open space, city leaders prioritized speed over safety. Buildings were reconstructed on the same street grid, using similar methods. The one significant improvement was an upgraded water system, including the construction of a high-pressure auxiliary water supply system (AWSS) with dedicated cisterns and hydrants specifically designed for firefighting — a system that remains in use today.

The city also expanded into areas made newly available by the destruction of Chinatown and the waterfront. The Marina District was created by filling in a lagoon with rubble from the earthquake — a decision that would have devastating consequences in 1989.

San Francisco earthquake risk today

Scientific Legacy

Reid's Elastic Rebound Theory

The 1906 earthquake triggered the most comprehensive scientific investigation of an earthquake ever conducted up to that time. Andrew Lawson of the University of California, Berkeley led the State Earthquake Investigation Commission, which produced a landmark two-volume report in 1908 — the "Lawson Report."

The commission's work included detailed mapping of the fault rupture along its entire 477 km length, documenting offsets in roads, fences, tree lines, and streams. This field data became the foundation for Harry Fielding Reid's elastic rebound theory, published in 1910. Reid proposed that earthquakes occur when accumulated strain along a fault is released suddenly, with the rocks on either side of the fault snapping back to their original undeformed positions — like a stretched rubber band being released.

This was a revolutionary insight. Before Reid, the cause of earthquakes was poorly understood. His elastic rebound theory remains the fundamental model for understanding tectonic earthquakes to this day, and it grew directly from the observations made along the San Andreas Fault after 1906.

Understanding what causes earthquakes

Fault Mapping and Seismology

The Lawson Report also produced the first comprehensive map of the San Andreas Fault, tracing it for hundreds of miles through California. This mapping established the fault as a major continental-scale feature and laid the groundwork for later understanding of plate tectonics.

The earthquake was also one of the first to be recorded on seismographs worldwide. Analysis of these records helped establish the global seismograph network and contributed to the development of earthquake magnitude scales in subsequent decades.

The Cover-Up

In the weeks and months after the disaster, San Francisco's business and political leaders mounted a deliberate campaign to minimize the earthquake's role and attribute the destruction primarily to fire. Their motivation was economic: if the disaster was understood as an earthquake, investors and insurers might view San Francisco as too risky for investment. If it was merely a fire — a risk common to all cities — the damage could be framed as a recoverable setback.

The Southern Pacific Railroad, one of the city's most powerful institutions, was particularly aggressive in this effort. The railroad's publicity department distributed pamphlets emphasizing the fire and downplaying the earthquake. Real estate interests lobbied successfully to have the event referred to as "the Great Fire" rather than "the Great Earthquake."

This campaign had real consequences. By framing the disaster as a fire rather than an earthquake, city leaders undermined public understanding of seismic risk. Building codes were updated to improve fire resistance but did little to address earthquake vulnerability. The word "earthquake" was effectively banished from polite conversation in San Francisco business circles for years.

The cover-up also suppressed the death toll. The official count of 478 was produced by a city government that had every incentive to minimize the disaster's apparent severity. It would take decades for researchers to arrive at the more accurate figure of approximately 3,000 deaths.

The consequences of this denial persisted. When the 1989 Loma Prieta earthquake struck, it revealed vulnerabilities — in the Cypress Viaduct, the Bay Bridge, and the Marina District — that had gone unaddressed in part because of San Francisco's long-standing reluctance to confront its seismic reality.

Current earthquake risk in San Francisco

Map Specification

Map: 1906 San Francisco Earthquake — Fault Rupture, Fire Zone, and Damage Areas

• Base map: Northern California coast and San Francisco city detail
• Fault rupture: 477 km San Andreas Fault rupture from San Juan Bautista to Cape Mendocino, highlighted in red
• Epicenter: Marked offshore near Mussel Rock, ~3 km west of San Francisco
• Fire zone: Shaded overlay showing the 4.7 sq mile burned area (east of Van Ness Avenue, south of Market Street, waterfront areas)
• Key points: Valencia Street Hotel, City Hall, Van Ness Avenue firebreak line, Chinatown, Nob Hill, Presidio refugee camps, Golden Gate Park refugee camps
• Maximum displacement marker: Olema (6.1 m offset)
• Inset map: Full fault rupture length along California coast

Chart Specification

Chart: Comparison of Earthquake Damage vs. Fire Damage in 1906

• Type: Stacked bar chart or proportional area chart
• Data:
  • Buildings damaged by earthquake shaking alone: ~5% of total losses
  • Buildings damaged by fire: ~90% of total losses
  • Buildings damaged by dynamiting: ~5% of total losses
• Source: Estimates from USGS and historical analyses (exact proportions vary by source, but fire damage consistently estimated at 80–90% of total losses)
• Note: Illustrates why the earthquake was reframed as "The Great Fire" — fire truly did cause the majority of physical destruction

Sources

1. Lawson, A.C. (1908). The California Earthquake of April 18, 1906: Report of the State Earthquake Investigation Commission. Carnegie Institution of Washington, Publication No. 87.
2. Reid, H.F. (1910). The Mechanics of the Earthquake, Volume II of the Lawson Report. Carnegie Institution of Washington.
3. Hansen, G. & Condon, E. (1989). Denial of Disaster: The Untold Story and Photographs of the San Francisco Earthquake of 1906. Cameron and Company.
4. USGS (2006). "The Great 1906 San Francisco Earthquake." USGS 1906 Earthquake Page
5. Winchester, S. (2005). A Crack in the Edge of the World: America and the Great California Earthquake of 1906. Harper Collins.
6. Tobriner, S. (2006). Bracing for Disaster: Earthquake-Resistant Architecture and Engineering in San Francisco, 1838–1933. Heyday Books.
7. USGS (2015). "UCERF3: A New Earthquake Forecast for California's Complex Fault System." UCERF3 Fact Sheet
8. Fradkin, P.L. (2005). The Great Earthquake and Firestorms of 1906. University of California Press.