INTEGRATED APPLICATION OF ASTER, LANDSAT, CORONA, AND SRTM DATA TO TECTONOSTRATIGRAPHIC MAPPING IN THE NEPAL HIMALAYA

I build upon field observations in the Thakkhola graben area of central Nepal using high-resolution CORONA satellite imagery, multispectral Landsat and ASTER scenes, and SRTM digital topography. Use of such data, particularly when tied to ground truth from available field observations, is a powerful approach to synoptic mapping of otherwise inaccessible terrain. In addition, it can provide regional geologic context for spatially distributed, detailed ground observations. However, particularly in temperate, mountainous terrain, difficulties associated with vegetation, snow and ice cover, and shadowing can make remotely sensed observations and interpretations difficult. With two case studies centered on the Thakkhola graben, I illustrate methodologies for mapping granitic igneous and phyllitic metamorphic units by employing decorrelation stretched imagery, index mapping, classifications, and photointerpretation methods. "Forced-decorrelation" processing is applied to image spectra to diminish the effect of patchy vegetation and other cover, and digital topography is used for constraining the geometry of mapped structures. Integrating the results of the digital image processing yields insights into the tectonic evolution of the study area, in particular the role played by crustal flow in establishing patterns of faulting and tectonostratigraphy.