San Francisco Earthquake - 1906

City Hall after the earthquake.

Introduction

In the early morning hours of April 16th, 1906; a earthquake struck the city of San Francisco. The epicenter of the of the earthquake was near the city of San Francisco, the foreshock (a shockwave that precedes the main waves of the earthquake) was felt at 5:12 am. The earthquake itself started less then a minute after the foreshock, the waves of the quake lasted up until a minute. While the quake was centered in the San Francisco bay area, people reported feeling the shock in much of the west coast area and inland as well.

Arnold Genthe photo showing Sacramento Street and approaching fire.

Geologic Processes

The San Francisco area lies San Andreas fault and a triple junction to the north of the city. At the time of the Earthquake, the fault now know as the San Andreas was know as the Tomales-Portola Fault. Much of the city in 1906 was built in the valleys that are around the bay, unlike bedrock, these valley are filled with sediment that ismore prone to stronger shaking from the quake because it is no a solid mass. This combination of faults along with the make up of the earth under the city helps to explain the damage that the quake caused.

Street sunken by earth movement. Note the curb and lamp post for referance to how much the street has moved.

290 miles of the San Andreas fault were affected by the Earthquake. Numbers for the amount of slip vary, but the newest numbers suggest that it was up to 28 feet in some areas. There are many different estimates for the intensity of the Earthquake, although there were seismographs that did pick up the Earthquake at the time it happened, there have been many advances in data collection and technology that have helped to refine the estimated intensity. The most persuasive number is 7.7, which was come to by a team that studied the originaldata. While there have been stronger Earthquakes, this was one of the first one in the Continental US that was looked at by scientist so to help prevent the damage that happened.

Products of the Geologic Process

A buckled trolly tracks, caused by earth flow.

There were 3000 deaths that were caused by the earthquake in San Francisco and the surrounding area, although most of those deaths were caused by building collapsing, not the earthquake itself. More then 250,000 people where left homeless by the Earthquake and the 3 day fire that followed. The population of San Francisco at the time was 400,000.

Photograph of the Damage. NARA - Office of the Signal Corps: NWCS-S - 111-SC-95101

The three day fire that followed the Earthquake was started by fires in home, since many of the morning breakfast fires had been lit at the time of the Earthquake. Also there was much displacement of streets and ground, as seen in the photos; this exposed gas lines which only furthered the fire. The fire caused more damage then the Earthquake, the area that was burned covered 4.7 square miles. This was the major affect on the city after the Earthquake.

Burning of the Mission District. NARA - Office of the Signal Corps: NWCS-S -111-AG-10

Literature Cited

Berkeley Seismological Labritory."Where can I learn more about the 1906 Earthquake?" http://seismo.berkeley.edu/seismo/hayward/seismicity.hist_1906.html

Geschwind, Carl-Henry. California earthquakes : science, risk, and the politics of hazard mitigation. Baltimore : Johns Hopkins University Press, 2001.

Morris, Charles. The San Francisco calamity by earthquake and fire [etc.]. The J. C. Winston co., 1906.

Museum of the City of San Francisco http://www.sfmuseum.org/1906/06.html

Municipal Report on "THE SAN FRANCISCO EARTHQUAKE AND FIRE OF APRIL 1906". Published by Order of the Board of Supervisors,1907. http://americahurrah.com/SanFrancisco/MunicipalReports/1906/Index.html

National Archives and Records Administration - Still Picture Branch. Personal Research.

National Archives and Records Administration -Civilian and Military Textual Branch. Personal Research.

Source Study of the 1906 San Francisco Earthquake. David J. Wald, Hiroo Kanamori and Donald V. Helmberger. http://pasadena.wr.usgs.gov/office/wald/1906/1906.html

USGS: Earthquakes Hazzards Program - Northern California. "The Great 1906 San Francisco Earthquake".
http://quake.wr.usgs.gov/info/1906/.html

Link to other Student Webpages for 2005 Earlham Physical Geology

Copyright © 2005 Earlham College. Revised April 11, 2005 . Send corrections or comments to parkero@earlham.edu