SEISMIC HAZARD ZONES FOR EARTHQUAKE-INDUCED GROUND FAILURE IN THE SAN FRANCISCO BAY AREA - MAPPING STATUS AND RELEASE OF NEW LANDSLIDE INVENTORY MAPS

The California Geological Survey (CGS) has released 19 official Seismic Hazard Zone Maps in the San Francisco Bay Area and is currently preparing 13 more that will be released over the next one to two years. The maps show Zones of Required Investigation for earthquake-triggered ground failure: specifically earthquake-induced landslides and liquefaction.

More than 40 cities in four counties in the San Francisco Bay Area are covered by the Seismic Hazard Zone Maps that have been completed or are now in preparation. The maps will be used by cities and counties to assist them in their responsibility to protect the public from the effects of earthquake-triggered ground failure as required by the Seismic Hazards Mapping Act.

California's Seismic Hazard Mapping Program is the most comprehensive government-mandated seismic zoning program in the U.S. and possibly the world. Ultimately, seismic hazard zones will be delineated for hundreds of city and county jurisdictions in California that are exposed to high seismic risk.

In addition to the seismic hazard zone maps, CGS has released or is planning to release numerous other data and maps that are generated during the preparation of seismic hazard zone maps. Currently, some data and several small-scale maps are presented in Seismic Hazard Zone Reports that are released with each map. These reports summarize the geology and seismology conditions and the liquefaction and landslide analyses that were performed.

CGS is now planning to release Landslide Inventory Maps for each of the Seismic Hazard Zone Maps that have been or soon will be completed – so far, more than 100 in northern and southern California. The Landslide Inventory Maps will be released on USGS 7.5-minute topographic bases and will include detailed symbology to depict significant features such as landslide type, depth, activity and confidence. These maps will be useful to planning and design professionals in the public and private sectors. Examples of CGS's new Landslide Inventory Maps as well as a summary of other planned data releases associated with the Seismic Hazard Mapping Program will be displayed.