American Society of Civil Engineers


Predicted Sedimentary Record of Reflected Bores


by Bretwood Higman, (Earth and Space Sciences, University of Washington, Johnson Hall 070, Box 351310, 4000 15th Ave. NE, Seattle, WA 98195-1310 E-mail: Hig314@U.Washington.edu), Guy Gelfenbaum, (USGS, 345 Middlefield Rd., MS999, Menlo Park, CA 94025 E-mail: GGelfenbaum@USGS.gov), Patrick Lynett, (Coastal and Ocean Engineering Division, Department of Engineering Texas A&M University, College Station, TX 77843-3136 E-mail: PLynett@civil.tamu.edu), Andrew Moore, (Department of Geology, Kent State University, Kent, OH 44242 E-mail: AMoore5@Kent.edu), and Bruce Jaffe, (USGS, 345 Middlefield Rd., MS999, Menlo Park, CA 94025 E-mail: BJaffe@USGS.gov)

pp. 1103-1116, (doi:  http://dx.doi.org/10.1061/40926(239)85)

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Document type: Conference Proceeding Paper
Part of: Coastal Sediments ’07
Abstract: Where a steep slope blocks an inrushing tsunami, the tsunami commonly reverses direction as a reflected bore. A simple method for relating vertical and horizontal variation in sediment size to output from numerical models of depth-averaged tsunami flow yields predictions about the sedimentary record of reflected bores: 1. Near the reflector, a abrupt slowing of the flow as the reflected bore passes is recorded by a normally graded layer that drapes preexisting topography. 2. At intermediate distances from the reflector, the deposit consists of a single normally graded bed deposited preferentially in depressions, possibly including a sharp fine-over-coarse contact. This contact records a brief period of erosion as the front of the reflected bore passes. 3. Far seaward of the reflector, grading in the deposit includes two distinct normally graded beds deposited preferentially in depressions separated by an erosional unconformity. The second normally graded bed records the reflected bore.


ASCE Subject Headings:
Predictions
Sediment
Tsunamis