A look back at the 1906 Great San Francisco Earthquake


The Great San Francisco Earthquake of 1906 was one of the deadliest earthquakes of recent times. The quake ruptured the 296 miles of the north San Andreas Fault in California, displacing land along the rupture zone. The quake caused multiple aftershocks, fire throughout San Francisco, shaking damage across the affected area, and a high death toll, particularly in San Francisco, but also in surrounding regions. The earthquake is considered one of the most devastating natural disasters in American history. For more information regarding the Great San Francisco Earthquake of 1906, watch the USGS video below.

If contemporary scientists had known about plate movement, they could have deduced that the quake was caused by subduction of the Pacific Plate beneath the North American Plate, resulting in a sudden release of energy courtesy of elastic rebound. The Plate Tectonics Theory would not be adopted until the mid twenty-first century. Scientists thought that the San Andreas Fault caused the earthquake, rather than the earthquake causing the fault. Professor H.F. Reid of Johns Hopkins University reversed this theory in his “Theory of Elastic Rebound”. The theory explains the series of events that ultimately leads to earthquakes. Plate motion folds and elastically distorts the crust until the accumulated strain in the crust is released, creating large seismic waves that shake the crust violently. The energy release is triggered by sudden tectonic plate or local land mass motion. Reid reached this theory by examining ground displacement resulting from movement of the San Andreas Fault during the 1906 quake. Check out the video below for an explanation of the Theory of Elastic Rebound and its relation to the San Andreas Fault in California.

The San Andreas Fault is a plate boundary transform fault striking northwest to southeast in California, USA. The fault is on the tectonic boundary between the North American Plate and the Pacific Plate, with strike slip motion, in which the crust on either side of the fault rubs against each other in a horizontal fashion. Geologist Andrew Lawson of UC Berkeley first discovered the fault in 1985. He found several landforms that marked the fault on regional topography, such as ground displacement, fault-oriented streambeds and river valleys, and several lakes.

EarthScope, the National Science Foundation, and the US Geological Survey monitor the San Andreas Fault with a program called SAFOD (San Andreas Fault Observatory at Depth). Boreholes are drilled near the fault zone and used to monitor the movement and processes associated with the fault. Hopefully, this program will add to geologist understanding of how faults work, whether movement can be predicted, and how earthquakes and faults interact to affect human populations. For more information, visit the Earthscope website or the USGS website.

1960-1 post_and_frant_avenue

Some photographs taken after the earthquake display the widespread destruction in San Francisco resulting from the event. Visit the 1906 Earthquake website for more information.