HR: 17:45h
AN: T22E-08    [PDF]
TI: Tectonics from topography: Methods, Application, and Limitations
AU: * Whipple, K X
EM: kxw@mit.edu
AF: Department of Earth, Atmospheric, and Planetary Sciences MIT, 77 Massachusetts Ave, Cambridge, MA 02139 United States
AU: Wobus, C
EM: cwobus@mit.edu
AF: Department of Earth, Atmospheric, and Planetary Sciences MIT, 77 Massachusetts Ave, Cambridge, MA 02139 United States
AU: Kirby, E
EM: ekirby@geosc.psu.edu
AF: Department of Geosciences Penn State University, 218 Deike Bldg, University Park, PA 16802 United States
AU: Snyder, N P
EM: nsnyder@usgs.gov
AF: USGS Pacific Science Center, 1156 High St., Santa Cruz, CA 95064 United States
AB: Empirical observations from fluvial systems across the globe reveal a consistent power-law scaling between channel slope and contributing drainage area. Theoretical arguments for both detachment and transport limited erosion regimes suggest that rock uplift rate should exert first-order control on this scaling. Here we describe in detail a method for exploiting this relationship, in which topographic indices of longitudinal profile shape and character (stream profile concavity and steepness indices) are derived from digital topographic data. Key data handling steps include sub-sampling at uniform vertical intervals to recover contour crossings in source vector data and to more evenly distribute data in log(S)-log (A) space. In addition, we test several approaches to further smoothing data to improve the noise-signal ratio. These tests reveal that stream profile concavity and steepness indices are not sensitive to the various smoothing options considered, but that smoothing does greatly improve one's ability to recognize scaling breaks otherwise hidden in the noise. The stream profile data can then be used to delineate breaks in scaling which may be associated with tectonic boundaries. In the San Gabriel Mountains, CA, analyses of USGS 10m, USGS 30m, SRTM 30m, ASTER 30m, and SRTM 90m DEMs differ in detail, but overall yield similar results. The description of the method is followed by three case studies from varied tectonic settings. The case studies illustrate the power of stream profile analysis in delineating spatial patterns of, and in some cases, temporal changes in, rock uplift rate. Owing to an incomplete understanding of river response to rock uplift, the method remains primarily a qualitative tool for neotectonic investigations; we conclude with a discussion of research needs which must be met before we can extract quantitative information about tectonics directly from topography.
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 8107 Continental neotectonics
SC: Tectonophysics [T]
MN: 2003 Fall Meeting