SAN FRANCISCO BAY AREA GEOLOGIC MAPS IN GOOGLE EARTH

We present a method to deliver detailed geologic data for the greater San Francisco Bay Area through Google Earth. Layers include previously published GIS databases of geology, liquefaction susceptibility, historic and prehistoric landslides, quaternary faults, and historic earthquakes (animated with time).

Complex geologic maps result in large file sizes, which slow down network and CPU performance on the user’s end. To provide more efficiency, we break down large GIS datasets into smaller KML 7.5’ quadrangle tiles using ESRI’s ArcInfo software. This conversion process employs several geoprocessing tools and third-party extensions. The data are organized and delivered through a web site where users have the option to browse data by theme, or to design unique maps for each quadrangle. Web links are provided to the source data and supplementary information about the geologic feature of interest.

Delivering data through Google Earth is a low cost alternative to web map services that are expensive and time intensive to maintain. Further, Google Earth is widely used and recognized by the public. The ability to stack geologic features on top of Google Earth’s high resolution imagery and cultural data is particularly important as the degree of shaking and resulting damage due to an earthquake is dependent on the geology and proximity to faults. This effort is intended to provide access to relevant geologic data to diverse audiences and to provide an educational tool for earthquake hazards in the Bay Area.