San Francisco Bay Region Geology and Geologic Hazards

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Sonoma County Coast - LIDAR Fault Mapping

Because faults generate recognizable shapes in the landscape (called fault geomorphology), geologists use those shapes to map out the location of active faults.  However, in many areas the faulted landforms are obscured by extensive vegetation. One of the newest tools for mapping faults is Laser Imaging Detection And Ranging (LIDAR, also known as LIght Detection and Ranging). LIDAR uses laser light projected from an airplane to make a detailed image of the ground surface, even through trees. This technique has been used to make a detailed map of the San Andreas Fault along the Sonoma and Mendocino County Coast from Fort Ross to Point Arena.

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This figure shows how LIDAR can help reveal active faults. (Left) A regular aerial photograph of an area of trees obscuring part of the San Andreas Fault zone in Sonoma County. (Center) The same area in a computer rendering of LIDAR data to "virtually" remove the trees and other vegetation. Scarps and other landforms associated with the Quaternary-active fault are now much easier to see. (Right) Fault strands traced onto the LIDAR image.

 

Learn more about the San Andreas Fault and its geomorphology at:

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