Thesis (M.Sc.)--Memorial University of Newfoundland, 2000. / Bibliography: leaves 114-119.

Thesis (Ph. D.)--Memorial University of Newfoundland, 1997. / Bibliography: leaves 180-187. Also available online.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2007. / Includes bibliographical references (leaves 95-97). Also available online.

The development of improved models of seismic diffraction is assisted by the availability of accurate scattering data. An acoustic scatter-mapping system was developed for the purpose of providing such data rapidly and at low cost. This system uses a source-receiver pair suspended on a trolley over the structure to be mapped. Signal generation, acquisition, processing, and plotting are performed on an AT-compatible microcomputer and a laser printer. The entire process can be performed in an automated manner within five hours, generating scatter-mapping plots in a format familiar to the geophysical industry. The system hardware was similar to those of Hilterman [1] and others referenced by him, but used a controlled source transducer. The available processing power of a microcomputer allowed the use of a 1 to 15 KHz swept-frequency source signal, similar to that used in Vibroseis and Chirp Radar, which is later crosscorrelated with received signal to provide precise scatter-mapping data for the target structure. Several examples of theoretical and experimental acoustic scatter-mappings are provided for comparison. The novelty of this system lies in its use of a swept frequency source signal. While common in the fields of seismology and radar, swept frequency source signals are new to the area of acoustic scatter mapping. When compared to a similar system using a pulsed source signal, this system produces a better controlled source signal of greater energy, resulting in a more useful resultant signal and better mapping characteristics. The system was able to map scattering from features in the target structure smaller than one percent of the crosscorrelated source signal's 37 mm dominant wavelength. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Thesis (Ph. D.)--University of Wyoming, 2005. / Title from PDF title page (viewed on Nov. 1, 2007). Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 181-191). Available also in a digital version from Dissertation Abstracts.

The crustal structure of a young (<10 My) ocean basin is imaged by two multichannel seismic reflection lines comprising 230 km recorded over the central part of the northern Juan de Fuca plate off western Canada. The more northerly line ties previously interpreted deep seismic reflection lines across the Juan de Fuca ridge and the Cascadia subduction zone; the southern line ties with another interpreted line across the subduction zone. Both lines trend obliquely to the spreading direction. A marine refraction profile crossing the eastern end of the lines provides velocity constraints. The processing sequence applied to the data includes a prestack inside-trace mute of CMP gathers to reduce noise levels on the deep data, CMP stack, post-stack dip filtering, f-k migration and bandpass. Coherency-filtered stacks are helpful in tracing weaker reflectors. The stacked sections reveal a horizontally layered sedimentary sequence overlying a rugged and prominent basement reflector dipping slightly landward. A strong, fairly continuous reflection from the base of the crust at about 2 s two-way-time below the basement surface generally mimics the basement topography and shows the characteristic doubling and tripling of reflections seen in other similar surveys. Although in general the crust appears acoustically transparent, weaker, discontinuous intracrustal reflectors are observed over 40 km at the eastern end of the northern line, and are interpreted to arise from the oceanic Layer 3A/3B and Layer 2/3 boundaries. The im-persistence of these reflectors is an indication of the complexity of the processes producing intracrustal reflectivity, and an indication of the lateral variability of crustal formation. Pseudofault traces of propagating rifts are crossed at three different locations on the two lines, the first MCS crossings of such structures. Crust associated with the pseudofault traces is related to both subhorizontal and dipping subcrustal events which are interpreted as zones of crustal thickening or underplating. Although the crustal thickness elsewhere on the lines varies by only about 10%, crust associated with the pseudofaults is as much as about 25% thicker than average, suggesting that magma supply at transform-type offsets may at times be large. A small seamount discovered on the southern line may result from the excessive magma production at the ridge postulated at propagating rift zones. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate