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California: Seismic Hazards

By National Geological and Geophysical Data Preservation Program
Image: Northridge, CA Earthquake Damage
Sources/Usage: Public Domain. View Media Details
Collection of USGS still images taken after the January 17, 1994 Northridge earthquake highlighting the damage to buildings and infrastructure. (Credit: USGS. Public domain.)

For the 2014 NGGDPP grant opportunity, the California Geological Survey (CGS) proposed to convert multiple databases containing geologic/geophysical borehole and scanned reports into a unified database. The geologic data contained within the database are associated with mandated liquefaction and landside assessment studies in Alameda County. The proposed project was designed to enable incorporation of additional metadata, with direct access links to digital files, with direct data for incorporation into the new database. Data from Alameda County were used as a test case, to establish data conversion and delivery processes. The database server was modernized to serve data over the Internet using web servicing techniques. The CGS requested and received $33,717 for the proposed work, which included 516 hours of student time.

The Seismic Hazards Mapping Act was passed by the California Legislature in response to the 1989 Loma Prieta earthquake. This legislation requires the CGS to delineate zones of required investigation where the probability of ground failure due to soil liquefaction or landslides is high. CGS determines the boundaries of these zones on the basis of engineering geologic and geotechnical engineering reports prepared by consultants for development projects, submitted to local governmental agencies to obtain building permits. Public access to these data improves future zoning and provides a ready data source for future projects and studies. The Seismic Hazard Mapping Act allows developers to waive the special studies requirement if they can provide existing data that shows a hazard does not exist on their site; access to the CGS data may prevent unnecessary expenditures that might limit otherwise economically viable projects. Many cities and some counties do not have data preservation plans in their offices. The CGS has found that these agencies dispose of the geotechnical report data soon after building permits are granted. In addition, consulting firms that prepare the data are frequently unwilling to grant access to their files or the reports are unavailable for other reasons, such as company buyouts or liability concerns. These issues make the data collected by CGS an invaluable resource for CGS and the public.