THE CALIFORNIA STRONG MOTION INSTRUMENTATION PROGRAM

The California Strong Motion Instrumentation Program, an earthquake engineering program in the California Geological Survey, Department of Conservation, was established following the damaging 1971 San Fernando earthquake to obtain critical strong motion data for engineering and earth science applications. SMIP has installed monitoring accelerographs to measure the motion of the ground and the response of structures in a variety of structures and free field locations throughout California over the last 38 years. The data gathered by the network is processed and disseminated to earthquake engineers, scientists, building officials and emergency personnel, and is used to assist emergency response and as a basis for improvements in building codes and seismic design.

The SMIP network has more than 1100 stations, including over 200 buildings, 75 bridges, 25 dams, 30 geotechnical arrays and 750 ground sites. All major toll bridges of the Dept. of Transportation, as well as the Golden Gate Bridge, are instrumented. Stations installed in the 1970s and 1980s were mostly analog, and required on-site recovery. In contrast, modern SMIP stations automatically telephone a bank of computers at SMIP headquarters in Sacramento when they record strong motion.

CGS/SMIP is a partner, along with the USGS, Caltech and UC Berkeley, in the California Integrated Seismic Network (CISN). With significant funding from the Calif. Emergency Management Agency, CISN provides earthquake information for emergency response, producing ShakeMaps of ground shaking within minutes after an earthquake identifying areas of the greatest likely damage.

Strong-motion data for engineering applications are distributed through the Center for Engineering Strong Motion Data (CESMD), a recent joint effort of the CGS and USGS initiated in 2006. The primary goal of the CESMD, at www.strongmotioncenter.org, is to provide rapid strong motion data after an earthquake, as well as ongoing access to previously recorded data, in both processed and raw form. As described in Haddadi et al. (this session), strong motion data from many earthquakes, and site conditons and information about recording stations, can be viewed and downloaded conveniently for use in engineering and earth science applications.