April 6, 2007
Contact: Ed Wilson
SACRAMENTO – April is traditionally Earthquake Preparedness Month, doubtless because the Great San Francisco Earthquake of 1906, the most destructive in California’s history, occurred during the month.
“But Californians need to be prepared for earthquakes year-round,” said Dr. John Parrish, California’s State Geologist and head of the California Geological Survey (CGS). “There’s a wildfire season, a tornado season, a flood season and a hurricane season, but earthquakes strong enough to do damage can and do occur at any time of year.
“California is a great place to live. But we need to realize that we live here by geologic consent. Earthquake Preparedness Month is the time for Californians to take stock of their personal preparation. Do you have an emergency kit, with water, food and medicine? Do you have a plan to regroup your family if you’re not together when a large earthquake occurs? These steps are useful not only for earthquakes, but for disasters such as floods and fires as well.”
Tips on what to do before, during, and after an earthquake can be found here. The CGS Website is loaded with information about earthquakes -- recent quakes, a list of California’s largest temblors, myths and basic background and definitions.
The last earthquake to cause a fatality in California – the magnitude 6.5 San Simeon temblor, which claimed two lives – occurred December 22, 2003. Earthquakes that have killed dozens of people – San Fernando, Loma Prieta and Northridge – occurred in 1971, 1989 and 1994, respectively.
“While earthquakes large enough to cause fatalities are few and far between, it stands to reason that the longer it’s been since the last one, the closer we are to the next one,” Parrish said. “Earthquakes are a fact of life in California. We cannot predict when they will occur. The best we can do is to take prudent steps in an effort to be ready.”
Because it hasn’t done so in more than 300 years, the southernmost segment of the San Andreas Fault is thought to be the most likely candidate to produce the next large earthquake. Starting on March 21, a small fault perpendicular to the San Andreas produced a swarm of more than 150 earthquakes in a five-day span near the Salton Sea. That prompted the California Earthquake Prediction Evaluation Council (CEPEC), chaired by Parrish, to convene. While no public announcement was made, CEPEC advised the California Emergency Management Agency to inform local emergency responders that there was a higher-than-normal likelihood of a major earthquake for a brief window of time following the swarm.
CGS has several programs geared at protecting public safety in the event of an earthquake, including:
♦ The Seismic Hazards Zonation Program addresses the hazards of liquefactions and landslides. Within identified zones, site-specific investigations must be done before new construction occurs, and mitigation steps for the hazards may be required. There are now 116 official Seismic Hazard Zone maps covering all or portions of nine counties.
♦ The Alquist-Priolo Earthquake Fault Zoning Program establish "earthquake fault zones" (AP zones) along known active faults. Affected cities and counties cannot allow development permits for sites within those zones until geologic reports show that the sites are not threatened by fissuring and shifting of the ground due to surface fault rupture. Currently there are 547 official maps affecting 36 counties and 104 cities.
♦ The Strong Motion Instrumentation Program (SMIP) installs monitoring devices called "accelerographs" throughout California to measure the vertical and horizontal response of structures and soils to strong earthquake shaking. The analysis of these data is used to recommend changes to engineering design codes and practices for the construction of buildings, bridges and other structures and to aid emergency response personnel in the event of a disaster. SMIP works in cooperation with the California Institute of Technology, UC Berkeley, and the U.S. Geological Survey to maintain a statewide network of instruments.