Lineament mapping with orbiting imaging radar

The Seasat A Synthetic Aperture Radar (SAR) was designed primarily for oceanographic and polar studies. During its 150-day mission before equipment failure, the SAR imaged substantial areas of North America as well as parts of northern Africa, Europe, Central America, and South America. The Seasat SAR differs from most commercial SLAR systems in that it has long wavelength (lambda = 25 cm) and a steep incidence angle ( approximately 20 degrees ). These factors make the system more sensitive to differences in surface materials. In the Peninsula Ranges of southern California, some previously unmapped lineaments were seen on radar images but not on Landsat. Field work has revealed faults of unknown displacement. Similar findings in the Appalachians have been reported. Near Medicine Lake and Mount Shasta in northern California, scarps only a few meter high are detectable. In that these small scarps have eroded to near the angle of repose and are parallel with the flight path, the energy return is particularly strong. In the course of this work we have developed a classification system for radar lineaments that includes physical models and predictions of effects of changing viewing geometry. Any attempt to analyze lineaments in smooth sedimentary basins should involve at least two viewing directions to minimize bias.