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NR 2006-10
April 14, 2006

Contact: Ed Wilson
Mark Oldfield
Don Drysdale
(916) 323-1886

CGS STRONG MOTION INSTRUMENTATION PROGRAM HONORED
 

SAN FRANCISCO – The California Geological Survey’s Strong Motion Instrumentation Program, which studies the effect of earthquake shaking on structures and soil to help guide engineering practices and protect public safety, has been honored as one of the top seismic programs of the 20th century by the Applied Technology Council.

“This award comes from an organization whose members use the data we produce, so this is a tremendous honor,” said State Geologist Dr. John Parrish, head of the California Geological Survey (CGS), part of the state’s Department of Conservation.

“We’re very pleased with and grateful for this recognition,” said Dr. Anthony Shakal, the Supervising Geologist in charge of the Strong Motion Instrument Program (SMIP). “The fact that the engineering community, which is the target of our work, recognizes the value of what we do tells us that we’re successful.”

The Applied Technology Council (ATC) is a nonprofit corporation headquartered in Redwood City. It was established in 1973 through the efforts of the Structural Engineers Association of California. ATC develops and promotes state-of-the-art, user-friendly engineering resources and applications for use in mitigating the effects of natural and other hazards on construction. ATC also identifies and encourages needed research and develops consensus opinions on structural engineering issues.

ATC’s board of directors includes representatives appointed by the American Society of Civil Engineers, the National Council of Structural Engineers Associations, the Structural Engineers Association of California, the Western Council of Structural Engineers Associations, and four at-large representatives concerned with the practice of structural engineering.

An ATC-commissioned jury selected award recipients. SMIP and the other winners will be honored at a joint ATC-Engineering News Record event April 17 – the eve of the centennial anniversary of the Great San Francisco Earthquake -- at the Westin St. Francs Hotel in San Francisco.

SMIP was established in 1971 after the devastating San Fernando earthquake to obtain vital data for the engineering and scientific communities through a statewide network of instruments. When activated by earthquake shaking, these “accelerographs” produce a record from which the critical characteristics of ground motion -- acceleration, velocity and displacement -- can be calculated.

The information is processed and disseminated to seismologists, engineers, building officials, local governments and emergency response personnel throughout the state. The data is used primarily to recommend changes to building codes, and assist local governments in their general plan process. SMIP also partners with the USGS, California Institute of Technology and UC Berkeley in the California Integrated Seismic Network. Real-time data collected by the network is used to produce a “ShakeMap” within minutes of a strong earthquake to help guide emergency response efforts.

SMIP has installed and maintains recording instruments at more than 1,000 locations statewide. The devices are housed in a variety of structures, including major bridges, high-rise buildings, dams, hospitals and industrial facilities. Among the instrumented sites are the city halls of Los Angeles, San Francisco and Oakland, and the state capitol. Accelerographs also are placed in open land to measure the motion of the ground and the effects of earthquake shaking on different types of soils. An advisory committee of engineers and scientists representing industry, government and universities help select SMIP’s station locations.

“I have a high regard for the work that SMIP does,’ said Christopher Rojahn, executive director of the ATC and a former research engineer involved in USGS’ strong motion program. “The program is very well organized. They’ve sought out the best advice in designing their program and provide a great service. The data SMIP got from its instrumentation in Parkfield is fundamentally important to our understanding of ground shaking.”

More than two decades of patience paid off for SMIP on September 28, 2004 when a magnitude 6.0 earthquake struck in Parkfield, a hamlet of 18 people located in rural southern Monterey County about midway between highways 5 and 101. The quake was centered almost directly underneath an array of 44 CGS and 10 USGS instruments. As a result, an unprecedented amount of information about how earthquakes work has been collected.

SMIP began placing instruments around Parkfield in 1982. Why there? Parkfield had experienced earthquakes in the magnitude 5.5-6 range every couple of decades going back to 1857. The 2004 event was a late arrival: the previous significant quake in the self-proclaimed “Earthquake Capital of the World” occurred in 1966.

Among the most interesting findings out of Parkfield: an oddity noted in the measured peak acceleration, or movement. Shaking occurred at about a third the force of gravity in Parkfield, which is about six miles northwest of the epicenter and within a half-mile of the main branch of the San Andreas fault. However, both northwest and southeast of the village, SMIP instruments measured shaking that was three times as intense as the shaking in Parkfield.

“We were stunned with how much the ground shaking varied over a relatively short distance,” Shakal said.

That knowledge has called into question whether one of SMIP’s goals – at least one seismic instrument in every California zip code – is adequate. But as Shakal noted, the data gathered at Parkfield showed the benefits of sticking with a plan.

“Our greatest success so far probably has been staying the course,” Shakal said. “Thanks in no small part to our advisory committee, our stations have been well-placed and we’ve done a good job of maintaining them in the long haul. Those two things go hand-in-hand. The excellent performance we received from our 20-year-old instruments at Parkfield is a tribute to our field technicians.”

Among SMIP’s current projects are the instrumentation of the new San Francisco Bay Bridge, several hospitals around the state, and wharfs at the Oakland, Long Beach and Los Angeles harbors. SMIP is also updating its older instruments, which capture ground shaking on film that has to be manually retrieved, with digital devices that report in real time to a central computer.


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