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A Quantitative Fracture Model for Initiation of Submarine Landslides
Final rept. 1 Jan 1996-31 Aug 1999
HAWAII UNIV HONOLULU DEPT OF GEOLOGY AND GEOPHYSICS
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Modeling the failure surface of a landslide as a three-dimensional shear fracture with an elliptical perimeter provides insight into incipient sliding process. The elastic boundary element model developed accounts for failure surface geometry, topographic slope, and gravity. As a region of sliding at depth grows, increasingly large stress concentrations develop near its perimeter. Once the slip surface length becomes several times greater than its depth, tensile stress concentrations near its head help drive the slip surface up towards the topographic surface to form a steep scarp from there the failure surface unzips down along the flanks. The model predicts opening of an arcuate pattern of echelon fractures at the surface at the slide head, normal faulting near the head, and thrust faulting at the toe, as is observed. Three other predictions stand out. First, notches are preferred sites for slide nucleation and should be avoided on slide-prone slopes. Second, arcuate cracks on a slope indicates that it is on the verge of failure. Third, crack patterns on the seafloor can be used to estimate the area, thickness and volume of potential slide masses, parameters important in assessing tsunami hazards due to submarine landslides.
APPROVED FOR PUBLIC RELEASE