Applications of Synthetic Aperture Radar Images to Map Geologic Structures and Geomorphology: Saint Elias Mountains, Alaska
Authors: Bruhn, R.L., Ford, A.L.J. and Forster, R.R.
Conference: American Geophysical Union Annual meeting
Dates: 13-17 December 2004
Abstract:The Saint Elias Mountains of southern Alaska and Canada are forming by collision of an allochthonous terrane at the northeastern end of the Aleutian subduction zone. The region represents one of the most dynamic glacial and tectonic systems on earth. Remote sensing is an important tool for interpreting structural and geomorphic features and processes in this remote and glaciated region of steep terrain and high relief where vegetation ranges from dense coastal conifer forest to alpine tundra. We use terrain corrected SAR amplitude images (brightness and radar backscatter) from the C-band ERS 1,2 and RADARSAT-1, and L-band JERS-1 imaging radars to evaluate the use of satellite borne radar for mapping structural and geomorphic features. Radar images are terrain corrected and draped upon 30 m posted digital elevation data obtained from the Shuttle Radar Topographic Mission flown in 2000. We have also written visualization software to interactively extract orientation data of structural features from 3D images including strike and dip of sedimentary rocks, faults, axial surfaces of folds, and contacts defined by angular unconformities. Geomorphic features of interest include fault scarps, braided river deposits, constructional and tectonically uplifted beach berms, wave cut terraces, rock and land slides, and glacial features including crevasse systems, moraines, and thermokarst topography. Orientation of crevasse systems on glaciers is automatically extracted using an algorithm based upon the directional anisotrpy of the 2D Fourier transform of radar images. The rate of transport of rock slide debris by glaciers is measured with a feature tracking algorithm applied to time-sequence imagery. L-band radar is superior to C-band for mapping geomorphic features of low topographic relief in densely vegetated lowlands. These include beach berms, relic river drainage patterns, and vegetated glacial topography. Radar response of structural features in bedrock is mostly controlled by hill slope and aspect, which produces similar response in radar brightness on both L- and C-band data in areas of modest to low vegetation density. We are continuing to evaluate the effects of radar polarization (HH vs VV), variability in beam incidence angle, and ascending and descending orbits on feature identification.
Source: Manual
Preferred by: Andrew Ford