New Department of Conservation maps show that a significant portion of Alameda County could experience landslides and unstable ground conditions during a major earthquake.
The California Department of Conservation released six Seismic Hazard Zone maps, which show that areas of Berkeley, Oakland, Hayward, Alameda, San Leandro, Emeryville and Albany could be affected by landslides and liquefaction during an earthquake of 6.0 or greater magnitude.
Liquefaction is a term used to describe areas of water-saturated sandy soil that may become unstable during earthquakes, leading to cracks in the ground and damage to buildings and structures, underground pipes and utilities.
Similar maps were released two years ago for the cities of Oakland and Piedmont. The new maps incorporate new information obtained through computer models and geologic explorations that included hundreds of borings performed by engineers.
The maps, which become official after a six-month review period – are used by city planners, developers and those who sell property and housing.
According to the Department of Conservation, the local building department must require developers to conduct geologic studies before any construction can take place on a property that is located in one of these “zones of required investigation.”
Also, those who sell property or real estate in these areas must inform their potential clients about the designation, much in the way that sellers in designated flood and wildfire zones must inform their customers about those designations.
Developers wishing to build in these areas must also turn in construction plans that show how they will address the problems, leading to better earthquake protection and less cost, since it generally costs more to seismically retrofit an existing building than it does to build in safety features at the design stages.
Each of the maps covers some 60 square miles. Black and white copies of the preliminary maps can be obtained by calling BPS Reprographic Services in San Francisco at (415) 495-8700. Color copies of the official maps will be available through the California Geological Survey by calling (415) 904-7707.
The maps can also be viewed online at http://gmw.consrv.ca.gov/shmp.