California infrastructureCalifornia prepares for major seismic event

Published 7 January 2011

Scientists are growing more wary about the potential for a major seismic event in California; earthquake trends show that intervals between such events have been as short as 45 years to as long as 145 years; considering that it has been 154 years since the last major quake, the San Francisco Bay Area, Delta Region, and Central Valley prepare for the worst

Aftermath of the 1906 San Francisco earthquake // Source: cehwiedel.com

The mainstream scientific community in California is growing more and more wary of the potential for a major seismic event. The last major event occurred was in 1857, and earthquake trends show that intervals between major events have been as short as 45 years to as long as 145 years. Considering that it has been 154 years since the last major quake, the San Francisco Bay Area, Delta Region, and Central Valley prepare for the worst.

A study titled “Uniform California Earthquake Rupture Forecast” was conducted in 2008 by the U.S. Geological Service (USGS), the California Geological Survey, and the Southern California Earthquake Center concerning the probabilities of future earthquakes. According to the study, it was projected that there was a 99 percent chance that a 6.7 magnitude earthquake would strike somewhere in California during the next thirty years. There were lower probabilities that such a damaging earthquake would strike specific areas within the state. The two faults that are more likely to generate catastrophic earthquakes of magnitude 7 or greater are the Hayward Fault, which runs down the east side of San Francisco Bay and last ruptured in 1868 (with an average recurrence interval of 140 years), and the southern portion of the San Andreas Fault, which has not ruptured for over 300 years.

The San Andreas Fault zone resides between two tectonic plates that traverse the western part of the state from the Colorado basin in the southeast, all the way up to the Bay Area in the north. According to the California Emergency Management Agency (Cal. EMA), “More than 70 percent of California’s population resides within 30 miles of a fault where high ground shaking could occur in the next 50 years. Statewide, approximately 22 million people live in the 40 percent or higher seismic hazard zone.”

Despite being unable to sanction any dependable method of predicting quakes, the California Earthquake Prediction Evaluation Council, a collaboration among several institutions, as well as the National Earthquake Prediction Evaluation Council, use kinetic frictional heating graphs and seismic hazard assessment maps to provide a picture of an earthquake of a given size affecting a given location. The USGS streams a listing of daily earthquakes on their Web site.

The Federal Emergency Management Agency (FEMA) maintains several grant programs that would provide funding to allay the effects of a major natural disaster. One of them, the $2.3 million Earthquake Hazards Reduction State Assistance