The Great M7.8 San Francisco Earthquake, April 18, 1906

110 years later, why the San Francisco Earthquake still matters

Wreckage of buildings from the M7.8 San Francisco earthquake. (from University of Nebraska at Lincoln Gallery of the Open Frontier)

The San Francisco Earthquake of 1906 was one of the most important geologic events of our time. Shaking damage destroyed many buildings, but it was the fires caused by severed gas lines during the earthquake that caused the city to burn for days after the shaking had stopped. More than 3,000 people are estimated to have died as a result, as well as 225,000 survivors left homeless by the 28,000 buildings that were destroyed. Check out the photo collections in these archives.

The earthquake itself was significant at an M7.8, but the damage it caused put into motion more intense focus on the study of earthquakes. This disaster spurred a movement for more scientific study of the geology and fault systems in California and eventually other locations along the coast. Read more about the “Dawn of Scientific Revolution” from the USGS.

How we are preparing for the next “big one”

Earthquake early warning systems like ShakeAlert work because the warning message can be transmitted almost instantaneously, whereas the shaking waves from the earthquake travel through the shallow layer of the Earth at speeds of one to a few kilometers per second (0.5-3 miles per second). This diagram shows how such a system would operate. When an earthquake occurs, both compressional (P) waves and transverse (S) waves radiate outward from the epicenter. The P wave, which travels fastest, trips sensors placed in the landscape, causing alert signals to be sent ahead, giving people and automated electronic systems some time (seconds to minutes) to take precautionary actions before damage can begin with the arrival of the slower, bur stronger S waves and later-arriving surface waves. Computers and mobile phones receiving the alert message calculate the expected arrival time and intensity of shaking at your location. USGS image created by Erin Burkett (USGS) and Jeff Goertzen (Orange County Register).

To try and mitigate damage and loss of  life, a coalition of scientists are working toward implementing an early warning system in California, Oregon, and Washington. Earthquake early warning (EEW) systems can measure earthquakes fast enough to transmit an alarm to cell phones and other reception sites to give valuable seconds of warning to prepare for the disaster.

According to the USGS Earthquake Hazards Program, a few seconds could give us enough time to:

  • Public: Citizens, including schoolchildren, drop, cover, and hold on; turn off stoves, safely stop vehicles.
  • Businesses: Personnel move to safe locations, automated systems ensure elevators doors are open, production lines are shut down, sensitive equipment is placed in a safe mode.
  • Medical services: Surgeons, dentists, and others stop delicate procedures.
  • Emergency responders: Open firehouse doors, personnel prepare and prioritize response decisions.
  • Power infrastructure: Protect power stations and grid facilities from strong shaking.

This prototype system, called ShakeAlert, will hopefully become fully functional in the coming years. Learn more about ShakeAlert, by watching a video here or reading this report.

As always, check out our Earthquakes and faults webpage to learn more about Washington’s mapped faults, and what to do before, during, and after an earthquake.

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