San Francisco Earthquake of 1906: San Andreas Fault Slippage Felt Over 375,000 Square Miles


An earthquake struck San Francisco, California on April 18, 1906. This major quake struck at 5:12 A.M. with a magnitude up to 8.3, lasting nearly one minute.

Quake Felt From Oregon to Southern California

A major earthquake struck San Francisco, and the coast of northern California, on Wednesday April 18, 1906, at 5:12 A.M. This quake was estimated at a magnitude of from 7.8 to 8.3. The main shock, lasting from forty-seven seconds to almost one minute, occurred about two miles offshore from this major California city. However, shaking from this quake was felt all the way from Coos Bay, Oregon, the state directly north of California, southward to Los Angeles and San Juan Bautista in Southern California. According to the U.S. Weather Bureau on Post Street in San Francisco, the quake was felt over an area of about 375,000 square miles.

San Andreas Fault

The quake ruptured all along the San Andreas Fault, California’s largest fault that is laced with other faults, from both north and south, in total a length of some 296 miles. It was also felt as far inland as central Nevada. The San Andreas Fault had slipped all the way from Fort Bragg, in the northern portion of the state, to the lower portion of Southern California.

After the main quake, one hundred and twenty aftershocks were felt that same day. And certainly, considerable damage had been done. But it is estimated that the fires that followed the quake, many a direct result of the quake, did more outright damage than the actual earthquake.

San Francisco on Fire

Due to results of the earthquake, gas mains were twisted and broken. The quake had caused hundreds of gas lanterns and burning candles to fall. Because of these two factors fires were nearly instantly set all over San Francisco. In the northeast, the most heavily populated portion of the city, some fifty separate fires were soon burning out of control.

Fire control as a means of putting out these raging fires was impossible. The water mains that ran up to the city, from some thirty miles to the south, were broken. The San Francisco Fire Department, its chief injured in the quake and dying, was helpless. Soon, the various and numerous fires merged into two major blazes that burned in three directions. The financial district, by the afternoon, was a mass of flames.

As evening approached the blazes had become an enormous firestorm which created a devastating wind. Ninety percent of San Francisco’s residences were built of wood. They had for the most part come through the quake but now they were nothing but dry kindling for the fire to consume.

Dynamiting to Stop the Fire

The army was called in to control looting but soon had an idea of its own for stopping the fires. They were authorized to dynamite the houses on the west side of Van Ness Avenue between Jackson and O’Farrell Streets.

The thought was to destroy burnable structures before the fire, itself, could reach them, burn them, and continue on with its destruction. It was later believed by many that this action only served to encourage the fire that raged for three more days.

Death Toll

Although only 375 deaths were initially reported, today’s estimate of the deaths the San Francisco Earthquake caused stands at some 3,000.

There were two major factors to the misrepresentation of the death total. The original low figure is said to have been concocted by government officials. Their reasoning, it is believed, was that they felt if they reported the correct death toll it would damage real estate prices as well as efforts in rebuilding San Francisco.

The second instance of misrepresenting the death toll was that, although there were hundreds of casualties in San Francisco’s Chinatown, these deaths were not considered to matter due to racism at the time. Also, there were 189 deaths in various locations across the San Francisco Bay area.

The Homeless and Refugee Camps

When the earthquake struck San Francisco this city stood as the ninth-largest city in the United States. With a population of some 410,000, San Francisco was the largest city on the entire West Coast. Because of the earthquake, somewhere between 225,000 and 300,000 people were left homeless. About half of these people fled to other areas across the Bay including Oakland and Berkeley.

Refugee camps were soon erected, the most noted being in Golden Gate Park. In addition, the Presidio, as well as the beaches between Ingleside and North Beach became covered with tents. As late as 1908, two years after the San Francisco Earthquake, many of the refugee camps were still being occupied.


  1. Cole, Tom. A Short History of San Francisco. Lexikos, San Francisco, California, 1981.
  2. Jeffers, H. Paul. Disaster By the Bay: The Great San Francisco Earthquake and Fire of 1906. The Lyons Press, Guilford, Connecticut, 2003.
  3. Winchester, Simon. A Crack in the Edge of the World: America and the Great California Earthquake of 1906. Harper Collins Publishers, New York, 2005.