Creation And Analysis Of A High Resolution Digital Elevation Model Of Northern Chile
This dissertation presents a digital elevation model (DEM) of the north Chilean forearc derived from interferometric synthetic aperture radar (INSAR). The DEM spans the Andean forearc from 18[DEGREE] S to 26[DEGREE] S latitude and is 99.1% complete. The coherence over the dataset is good to excellent, largely because of the ideal hyper-arid climate of the region for repeat-pass INSAR processing. The horizontal resolution of the data is 20 meters and the vertical resolution is 2-3 meters with an absolute vertical accuracy of 32 meters. We analyze a composite DEM from our 20-meter DEM and the 90-meter Cornell digital topography to create a fault scarp map based on scarps with youthfullooking profiles to examine Cenozoic faulting patterns in the forearc. Two fault patterns are evident in the fault map: 1) dominant N-S trending fault scarps controlled by pre-existing structures of the Atacama Fault System (AFS) south of 21[DEGREE] S and 2) a spatially-limited distribution of E-W trending fault scarps between 19[DEGREE] S and 21.5[DEGREE] S. We consider several regional factors that could be responsible for the E-W faults: climate, the AFS, aseismic ridge subduction, proximity to the Bolivian Orocline, and segment boundaries at the NazcaSouth America subduction interface. We conclude that the influence of oroclinal bending and a possible asperity on the plate interface acting as a segment boundary could explain the presence and containment of these anomalous structures. Finally, we validate the DEM with field-measured scarp profiles and find agreement to within the vertical errors of the DEM. Applying inverse scarp diffusion modeling to both field and DEM profiles, we are able to quantitatively identify two populations of scarp morphologies that correspond to proximity to the coast. Scarps closer to the coast have a steeper scarp face than those further inland. We hypothesize that coastal fog creates an erosionresistant gypcrete layer from the colluvium, which preserves fault scarp faces against diffusion, thus maintaining a younger morphology. These studies demonstrate a range of applications made possible by an accurate, high resolution, wide coverage digital dataset derived from INSAR.
dissertation or thesis