No description available.

Results from shallow-water observational studies have shown acoustic field fluctuations in excess of 10 dB due primarily to non-linear internal solitary waves (ISWs). This work concentrates on three limitations ISWs pose to shallow-water acoustic propagation: anisotropy, quasi-deterministic-stochastic nature, and frequency dependence. These aspects are explored for low frequencies of 75 and 150 Hz through the development of a full-wave three-dimensional parabolic equation model in which a single ISW is introduced and rotated to achieve differing geometries between the ISW and acoustic transmission path. Two acoustic scattering regimes were found to exist: A horizontal refractive regime that generates very intense acoustic energy focusing and shadow zones near the ISW at range when the acoustic transmission path is nearly parallel to the ISW crest, and a vertical mode coupling regime producing moderate to strong acoustic energy focusing and shadow zones for all geometries. These three-dimensional patterns are similar for each frequency, but more intense for 150 Hz. The results dramatically show ISWs focus acoustic energy, dependent upon frequency and geometry, which may be exploitable in both a sonar performance and ambient noise modeling sense. / US Navy (USN) author.

Thesis (doctoral)--K. Technische Hochschule zu München. / Includes bibliographical references.

No description available.

Thesis (M.S.)--University of Wisconsin--Madison, 1967. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

No description available.

(M.S.)--Brigham Young University. Dept. of Electrical and Computer Engineering. / Includes bibliographical references (leaves 63-64).

Thesis (M.S.)--University of Wisconsin--Madison, 1986. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 189-199).

Iceland has long been thought to be underlain by a thermal upwelling, or plume, rising from deep within the mantle. This study tests this hypothesis, by a) seeking evidence for a plume in the lower mantle in azimuth anomalies at the NORSAR array and b) mapping the three-dimensional structure of the mantle beneath Iceland using teleseismic tomography and data from an Iceland-wide broadband seismometer network. A temporary network of 30 digital broadband, three-component seismographs was deployed 1996-1998 to complement the existing, permanent seismic network on Iceland. This created a dense, well-distributed network. 3159 P-wave and 1338 S-wave arrival times were measured and inverted for velocity structure using the ACH method of teleseismic tomography. The preferred models are well-resolved down to -400 km, and reveal a low-velocity body with anomaly up to -2.9% in V(_p)) and -4.9% in V(_s) beneath central Iceland. This persists throughout the entire model depth range. The amplitudes of the anomalies imply an excess temperature of 200-300 K relative to the surrounding mantle. The morphology of the anomaly changes from cylindrical to tabular at 250-300 km depth, a feature that resolution tests suggest is real. This is consistent with the predictions of some convection models and suggests that the plume is restricted to the upper mantle. Anomalies in v(_p) and v(_s) provide evidence for lateral flow of material beneath the Reykjanes Ridge to the southeast in the depth range 50-200 km. Similar anomalies are present beneath the Kolbeinsey Ridge to the north only beneath 160 km. This shows that flow outwards beneath the Kolbeinsey Ridge is blocked by the Tjörnes Fracture Zone above 160 km. Azimuthal anomalies detected on the NORSAR array for rays travelling beneath Iceland at 1,500 km depth are consistent with a plume beneath Iceland at this lower-mantle depth with a Gaussian radius of 125 km and a strength of 1.5%. The observations do not serve as proof for such an anomaly because the solution is not unique. V(_p)/V(_s) ratios are 1% high throughout most of the plume, and up to 3.2% high at depths of 100-300 km beneath central and east-central Iceland. This suggests that up to a few percent of melt pervades the entire plume.

No description available.