U.S. Geological Survey
Fact Sheet
photograph of the heavily forested area near Puget Sound with the trace of Toe Jam Hill Fault drawn in Discovering active faults in thickly vegetated regions, such as the Puget Sound area of Washington (photo), is very challenging because their topographic expressions are hard to see. However, a new airborne laser technology, called LIDAR (light detection and ranging), is fast changing this. LIDAR imaging can see through forests to permit high-resolution measurement of topography to a precision of a foot or less, showing otherwise invisible faults. Using LIDAR, the U.S. Geological Survey has been able to identify previously unknown faults in the Seattle and Puget Sound area. The LIDAR image at right reveals the Toe Jam Hill Fault, marked by a conspicuous east-west topographic trend (arrows). In addition, the image shows north-south grooves in the Earth’s surface that were formed by the movement of ancient glaciers.
data from the LIDAR instrument that showed scientists the location of Toe Jam Hill Fault

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URL of this page: https://pubs.usgs.gov/fs/2003/fs017-03/hidden.html/
Maintained by: Michael Diggles
Created: Februarh 16, 2003
Last modified: May 17, 2005 (mfd)