Browsing by Subject "Seafloor"
Now showing items 21-40 of 40
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Multistatic bottom reverberation in shallow water
(NATO. SACLANTCEN, 1997)A wavenumber integration approach to modeling of the full multistatic reverberant field produced by small-scale bottom roughness in stratified shallow water waveguides has been developed. A perturbation approach to rough ... -
Numerical modeling results for mode propagation in a wedge
(NATO. SACLANTCEN, 1987/11)A PE (parabolic equation) code is used to study propagation in a shallow water wedge with a penetrable bottom. Particular attention is given to "wedge modes" that have wave fronts that are arcs of circles centered on the ... -
Ocean-bottom reflectivity (a point of view)
(NATO. SACLANTCEN, 1975/10)The analysis procedures for extracting bottom loss values from pulsed acoustic signals that have interacted with the ocean bottom do not inherently consider sub-bottom refraction and reflection of sound, which are important ... -
Perturbation theory applied to sound scattering from a rough sea-floor
(NATO. SACLANTCEN, 1992/09)Perturbation theory is applied to acoustic scattering from a rough sedimental sea-floor. Realistic -
Qualitative aspects of seismograph-ocean bottom interaction
(NATO. SACLANTCEN, 1988/06)The parameters affecting the coupling of the Ocean Bottom Seismometer to the ground have been -
Reflection of sound from a layered ocean bottom
(NATO. SACLANTCEN, 1975/10) -
Refraction of sound in the sea floor
(NATO. SACLANTCEN, 1975/10)A major mode of propagation of acoustic energy at low frequencies is a shallow refracted path through unconsolidated sediments of the sea floor. Successful modelling of the bottom-refracted mode of propagation requires ... -
Relative contribution of surface roughness and bottom attenuation to propagation loss in shallow water
(NATO. SACLANTCEN, 1975/10)A simulation study has been performed to investigate the relative importance of the contributions of surface roughness and bottom attenuation to propagation loss under differing environmental conditionso The NRL normal ... -
Shallow seafloor geology and sediment character ofthe western Mallorca Platform
(NATO. SACLANTCEN, 1995/03)A site survey of the seabottom west of Mallorca in the central Balearic Islands has characterized the bottom and the immediate sub-bottom. High resolution seismic reflection Uniboom, deeper penetrating (about 5x Uniboom) ... -
Shear properties of ocean sediments determined from numerical modelling of Scholte wave data
(NATO. SACLANTCEN, 1986/06)Recently it has become apparent that shear properties of ocean sediments are most easily determined from measured propagation characteristics of seismic interface waves. We use a newly developed numeri ca l model of wave ... -
Single mode excitation, attenuation and backscatter in shallow water
(NATO. SACLANTCEN, 1995/10)Normal mode theory is used to illustrate that a vertical array of weighted sources driven in an -
Spectral integral representations of monostatic backscattering from three dimensional distributions of sediment volume inhomogeneities
(NATO. SACLANTCEN, 2001/03)A theory is developed for generating short time, monostatic reverberation realizations caused by three dimensionally distributed volume inhomogeneities in stratified media. A spectral integral approach to treating the ... -
Statistical evaluation of 80 kHz shallow-water seafloor reverberation
(NATO. SACLANTCEN, 1997)In this work a comparison is presented between 80 kHz reverberation statistics obtained at shallow water sites around Sardinia and Sicily. The data include measurements from several distinct bottom provinces, including ... -
Sub-sea floor buried reflectors imaged by low frequency active sonar
(NATO. SACLANTCEN, 1996/06)Low Frequency Active Sonar (LFAS) utilizes low-frequency acoustic -
The effect of a layer of varying density on high-frequency acoustic reflection, forward propagation loss and backscattering strength
(NATO. SACLANTCEN, 1997/06)This report examines the impact that a thin layer of varying density would have on high-frequency reflection, forward loss and backscattering of acoustic plane waves from the seafloor. A functional form for density ... -
The optimum frequency of propagation in shallow-water environments
(NATO. SACLANTCEN, 1983/04)The optimum frequency of propagation in shallow water environments is the result of competing propagation and attenuation mechanisms at high and low frequencies. It is shown that the optimum frequency is strongly dependent ... -
The sub-bottom structure of the Gulf of La Spezia
(NATO. SACLANTCEN, 1968/12)The sub-bottom structure of the Gulf of La Spezia, Italy, has been investigated by continuous seismic profiling and sediment coring. The seismic profiles were used to develop contour plots of sub-bottom layers, which were ... -
Time dependence of infrasonic ambient seafloor noise on a continental shelf
(NATO. SACLANTCEN, 1986/06)SACLANTCEN is conducting a long term programme of ambient noise measurements that cover the frequency band from 1 to 100 Hz. A sea-bed sensor consisting of three seismometers and a hydrophone has been deployed close to the ...