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    • Keywords


      Shear-wave velocity; site conditions; geomorphometry; terrain modeling; object-oriented; satellite data; Geophysics, Geomorphology; remote sensing.

    • Abstract


      Estimation of the degree of local seismic wave amplification (site effects) requires precise information about the local site conditions. In many regions of the world, local geologic information is either sparse or is not readily available. Because of this, seismic hazard maps for countries such as Mozambique, Pakistan and Turkey are developed without consideration of site factors and, therefore, do not provide a complete assessment of future hazards. Where local geologic information is available, details on the traditional maps often lack the precision (better than 1:10,000 scale) or the level of information required for modern seismic microzonation requirements. We use high-resolution (1:50,000) satellite imagery and newly developed image analysis methods to begin addressing this problem. Our imagery, consisting of optical data and digital elevation models (DEMs), is recorded from the ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) sensor system. We apply a semi-automated, object-oriented, multi-resolution feature segmentation method to identify and extract local terrain features. Then we classify the terrain types into mountain, piedmont and basin units using geomorphometry (topographic slope) as our parameter. Next, on the basis of the site classification schemes from the Wills and Silva (1998) study and the Wills et al (2000) and Wills and Clahan (2006) maps of California, we assign the local terrain units with $V_s$ 30 (the average seismic shear-wave velocity through the upper 30m of the subsurface) ranges for selected regions in Mozambique, Pakistan and Turkey. We find that the applicability of our site class assignments in each region is a good first-approximation for quantifying local site conditions and that additional work, such as the verification of the terrain’s compositional rigidity, is needed.

    • Author Affiliations


      Alan Yong1 Susan E Hough1 Michael J Abrams2 Christopher J Wills3

      1. United States Geological Survey, 525 South Wilson Avenue, Pasadena, CA 91106, USA.
      2. Jet Propulsion Laboratory/California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA.
      3. California Geological Survey, 801 K Street. MS 12–32, Sacramento, CA 95814, USA.
    • Dates

  • Journal of Earth System Science | News

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