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Geoacoustic scattering from seafloor features in the ROSE area

By
Martin E. Dougherty
Martin E. Dougherty
Massachusetts Institute of Technology/Woods Hole Oceanographic Institution Joint Program, Woods Hole, Massachusetts 02543
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Ralph A. Stephen
Ralph A. Stephen
Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543
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Published:
January 01, 2016

Abstract

A strong “refraction branch diffraction,” presumably due to scattering from a lateral heterogeneity on or below the seafloor, has been observed on ocean bottom hydrophone data from the Rivera Ocean Seismic Experiment (ROSE). This arrival is unusual because of its coherence and relatively large amplitude. Finite difference modeling of a number of possible seafloor diffractors and associated lateral velocity variations is presented, which demonstrates the occurrence and characteristics of “refraction branch diffractions.” In general, the half-width of the diffractor must be approximately the same as the seismic wavelength in order to produce a strong diffraction. Velocity gradients present in the models, as well as PS conversion, complicate the wavelength-half-width relationship. Three different models, a hill, a valley, and a subsurface high-velocity block, all produced diffractions of sufficient amplitude to explain the data. There is a hill along the line with approximately the same dimensions as the model hill and it is the proposed source of the diffracted energy in the data. The large models used also clearly demonstrate the existence of phases that are theoretically possible but rarely seen in the marine seismic (geoacoustic) data such as the pseudo-Rayleigh wave and the P and S interference head waves.

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Contents

Society of Exploration Geophysicists Geophysics Reprint Series

Seismic Diffraction

Kamil Klem-Musatov
Kamil Klem-Musatov
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Henning Hoeber
Henning Hoeber
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Michael Pelissier
Michael Pelissier
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Tijmen Jan Moser
Tijmen Jan Moser
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Society of Exploration Geophysicists
Volume
30
ISBN electronic:
9781560803188
Publication date:
January 01, 2016

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