Geoacoustic scattering from seafloor features in the ROSE area
Martin E. Dougherty, Ralph A. Stephen, 2016. "Geoacoustic scattering from seafloor features in the ROSE area", Seismic Diffraction, Kamil Klem-Musatov, Henning Hoeber, Michael Pelissier, Tijmen Jan Moser
Download citation file:
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.
Figures & Tables
The use of diffraction imaging to complement the seismic reflection method is rapidly gaining momentum in the oil and gas industry. As the industry moves toward exploiting smaller and more complex conventional reservoirs and extensive new unconventional resource plays, the application of the seismic diffraction method to image sub-wavelength features such as small-scale faults, fractures and stratigraphic pinchouts is expected to increase dramatically over the next few years. “Seismic Diffraction” covers seismic diffraction theory, modeling, observation, and imaging. Papers and discussion include an overview of seismic diffractions, including classic papers which introduced the potential of diffraction phenomena in seismic processing; papers on the forward modeling of seismic diffractions, with an emphasis on the theoretical principles; papers which describe techniques for diffraction mathematical modeling as well as laboratory experiments for the physical modeling of diffractions; key papers dealing with the observation of seismic diffractions, in near-surface-, reservoir-, as well as crustal studies; and key papers on diffraction imaging.