LIDAR Helps To Find Faults

NASA’s investment in airborne LIDAR (light detection and ranging) mapping technology is paying major dividends in an assessment of earthquake hazards in Washington state.

Dr. David Harding, a geophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Md., is working with local municipalities and the United States Geological Survey (USGS) to map earthquake hazards along the Seattle fault zone using commercial airborne LIDAR mapping capabilities.

The commercial benefits of LIDAR technology lie in its ability to map the topography of the ground where it is covered by vegetation, where LIDAR technology reveals much more detail at the surface than previous methods.

Until a LIDAR mapping survey was flown no surface trace of faults in the Seattle fault zone had been identified, neither on the ground nor from remote sensing, due to the dense vegetation cover of the Pacific Northwest temperate rainforests. Before LIDAR technology, aerial photographs were used to map surface features, but thick forest cover made locating the ground virtually impossible. Using LIDAR technology, scientists can filter out high measurements from leaves or branches above the surface to get a more accurate elevation map of the underlying ground.

Harding represents NASA in the Puget Lowland LIDAR Consortium that has contracted with Terrapoint, LLC of Houston to map a large region of the Puget Lowland, including the entire extent of the Seattle fault zone.

Terrapoint was funded by NASA to commercialize the airborne laser mapping system developed by Bill Krabill, a researcher at NASA’s Wallops Flight Facility, for the Arctic Ice Mapping program. Funding for the Puget Lowland mapping is being provided by a congressional appropriation to Kitsap County through the USGS, NASA’s Solid Earth and Natural Hazards program, the City of Seattle and the Puget Sound Regional Council.

The LIDAR image collected under the direction of Greg Berghoff at the KPUD, revealed a previously unrecognized fault scarp or an offset in the land surface formed by faulting, in the Seattle fault zone.

‘Natural hazard assessment is only one application of this mapping technique,’ says Harding. ‘Assessing stream quality for salmon spawning, documenting forest cover conditions, evaluating land use and urban sprawl, and floodplain mapping will also benefit greatly using LIDAR mapping technology.’

Harding says that the data from the Puget Lowland also will be used to test observations from NASA’s recently completed Shuttle Radar Topography Mission and from an upcoming LIDAR mission, the Ice, Cloud, and Land Elevation Satellite (ICESat).