HR: 10:35h
AN: T42B-02    [Abstracts]
TI: Critical Assessment of Quantitative Geomorphology in the Footwall of Active Normal Faults, Basin and Range Province, Western U.S.A.
AU: * Sorby, A P
EM: andrews@earth.ox.ac.uk
AF: Department of Earth Sciences, Oxford University, Parks Road, Oxford, OX1 3PR United Kingdom
AU: England, P C
EM: philip@earth.ox.ac.uk
AF: Department of Earth Sciences, Oxford University, Parks Road, Oxford, OX1 3PR United Kingdom
AB: Displacement rates of normal faults in the Basin and Range vary by several orders of magnitude across the province, yet the mountain ranges bounded by these faults demonstrate strikingly similar topography. The observed morphology of normal-fault bounded mountains reflects the balance of relative uplift and erosional processes, raising the question of whether detailed geomorphic studies can yield insight into rates of deformation on timescales important to the dynamics of deformation. Using USGS 30~m Digital Elevation Models we quantify the following geomorphic measures for 19 mountain ranges in northern Nevada: channel concavity ($\theta$), channel steepness index ($k_s$), hypsometric integral, mountain front sinuosity, and the skewness and kurtosis of surface slope distributions. Several measures commonly thought to be indicators of fault activity, in particular mountain front sinuosity and hypsometric integral, show weak correlation with vertical slip rate or no correlation at all. However, channel concavity, $\theta$, channel steepness index, $k_s$, hypsometric integral and the skewness of slope distributions within individual drainage-basins correlate significantly with vertical slip rate, and with one another. No obvious correlation with bedrock lithology or climate is observed. Principal component analysis demonstrates that the first two components account for 70% of the variance in the data. The first principal component is dominated by channel steepness index, concavity and kurtosis of slope distributions.
DE: 9350 North America
DE: 8100 TECTONOPHYSICS
DE: 8107 Continental neotectonics
DE: 8109 Continental tectonics--extensional (0905)
DE: 1824 Geomorphology (1625)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting