State Geological Survey issues new seismic maps
Tuesday, April 27, 2010
Officials of the California Geological Survey marked the agency's 150th anniversary Tuesday by releasing two updated maps revealing the latest information on all the state's active seismic faults, as well as details of its underlying geology.
"The detail and quality of the new maps is a point of pride, showing how far we've come as a survey in the last 150 years," said John Parrish, the state geologist and director of the agency during a ceremony at the Tech Museum in San Jose.
Copies of the maps were distributed to local students and their teachers, and Parrish said more copies in varied formats will be sent to every school, university, earthquake consulting firm and government agency in the state.
The agency was created in the wake of the Gold Rush to give miners detailed information on possible gold-bearing lands in the Sierra, and later was ordered by the Legislature to study and monitor earthquakes and the faults that trigger them.
The survey's new maps are interactive and linked to Googlemaps, enabling computer users to move across the entire state, selecting faults and specific geologic areas of interest. The agency is preparing even more high-tech versions that will enable users to zoom in close to specific areas and specific faults. The new maps will be released online to the public soon, said Lee Wallinder of the agency's graphics department.
The new geologic map, in full color, identifies the varied types of rock formations and soils that make up the state's entire surface and near-surface. It is based on data that have been accumulated since the first geologic map of the state was created in 1891. This is the fifth version - the last was issued in 1977.
Statewide maps showing fault activity were first issued in 1973, but while the state's geology itself hasn't changed, earthquake knowledge updates with every quake. The fault map is the fourth update since the first one was issued.
The Legislature created the state Geological Survey in 1860, 19 years before the much larger U.S. Geological Survey was formed. The agency now maintains more than 5,000 instruments that record strong ground motion from earthquakes at bridges, major buildings and hospitals. Those records provide data on how varied structures react to every significant shaking, and are used to strengthen building codes for resistance to quake damage.
New maps
The new state geologic map is at: links.sfgate.com/ZJOP
The fault map is at: links.sfgate.com/ZJOQ
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