The study, reported in the April issue of the journal Soil Dynamics and Earthquake Engineering, was conducted in a five-year collaborative research project initiated and directed by Franois Heuze, a geotechnical engineer at Lawrence Livermore National Laboratory (LLNL) near San Francisco. Seven UC campuses participated in the study, known as the Campus Earthquake Program. The researchers found wide discrepancies between their own seismic hazard estimates for the three campuses and those produced by current estimating techniques used for designing new buildings and retrofitting existing buildings.
"The biggest weakness in the current state of the practice for seismic hazard assessment," said Ralph Archuleta, professor of seismology at UCSB, "is that we have very little data for very large earthquakes where the site is close to the causative fault. UCSB, UCR, and UCSD all have major faults that are very close to the campus."
"A single estimate of ground motion for a site is not appropriate," said Heuze. "Even if you have a known fault and restrict your calculations to a known magnitude, this fault could provide that magnitude in many different fashions. Thus the severity of the ground shock where you stand could vary widely."
To try to overcome this problem, the researchers placed several seismic monitoring stations at each campus in boreholes up to 100 meters (330 feet) deep three times the depth of typical geophysical studies and collected data on small earthquakes from local faults as well as regional seismic events. They took and tested soil samples at various depths and simulated hundreds of possi
Contact: Charlie Osolin
DOE/Lawrence Livermore National Laboratory