The scattering of shear-waves in the crust |
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Authors: | Stuart Crampin |
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Institution: | (1) British Geological Survey, Murchison House, West Mains Road, EH9 3LA Edinburgh, Scotland, UK |
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Abstract: | The two major sources of scattering for shear-waves in the crust, interactions with the topography at the surface and the effective anisotropy of aligned cracks throughout the rockmass, introduce first-order changes to the shear-wave particle-motion. At the surface, shear-waves are scattered by the topography within a wavelength or two of the recording site so that, unless the effective incidence angle is less than the critical angle sin–1
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P, the recorded waveforms may bear little relationship to the waveforms of the incident wave. Within the rockmass, shear-waves are scattered by extensive-dilatancy anisotropy (EDA), the distribution of stress-aligned fluid-filled cracks, microcracks, and preferentially oriented pore-space pervading most rocks in the crust. Analysis of this shear-wave splitting yields new information about the internal structure of thein situ rockmass which is not otherwise available. |
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Keywords: | Shear-wave splitting extensive-dilatancy anisotropy EDA stress-aligned cracks surface interactions localSP-wave |
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