Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1980. / Microfiche copy available in Archives and Science. / Vita. / Bibliography: leaves 226-239. / by Steven R. Taylor. / Ph.D.

Thesis. 1976. Ph.D.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Microfiche copy available in Archives and Science. / Bibliography: leaves 174-183. / Ph.D.

Thesis. 1975. Sc.D.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Vita. / Bibliography: leaves 358-387. / Sc.D.

Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Microfiche copy available in Archives and Science. / Bibliography : leaves 241-256. / Ph.D.

Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Microfiche copy available in Archives and Science. / Vita. / Bibliography : leaves 263-277. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1979. / Bibliography: leaves 42-48. / by Janet Catherine Johnston Pruszenski. / M.S.

Approved for public release, distribution is unlimited / Landmines continue to be a threat to both military and civilian communities throughout the world. Current methods of detection, while better than nothing, could certainly be improved. Seismic SONAR is a promising new technology that may help save countless lives. The goal of this thesis was to advance Seismic SONAR development by introducing a mobile source which could be easily used in practical applications. A small tracked vehicle with dual inertial mass shakers mounted on top was used for a source. The source accurately transmitted the shaker signal into the ground, and its mobility made it a practical choice for field operations. It excited Rayleigh waves, as desired, but also generated undesirable P-waves and was not found to be directional. It proved incapable of finding a target. Improvements, such as a deploying an array of mobile sources and a stronger source, should vastly enhance the performance of such tracked vehicles in seismic SONAR mine detection and should be pursued. / Ensign, United States Navy

Ocean-bottom seismometers (OBS) allow wider angle recording and therefore, they have the potential to significantly enhance imaging of deep subsurface structures. Currently, conventional OBS data analysis still uses first arrival traveltime tomography and prestack Kirchhoff depth migration method. However, using first arrival traveltimes to build a velocity model has its limitations. In the Taiwan region, subduction and collision cause very complex subsurface structures and generate extensive basalt-like anomalies. Since the velocity beneath basalt-like anomalies is lower than that of high velocity anomalies, no first-arrival refractions for the target areas occur. Thus, conventional traveltime tomography is not accurate and amplitude constrained traveltime tomography can be dangerous. Here, a new first-arrival stochastic tomography method for automatic background velocity estimation is proposed. Our method uses the local beam semblance of each common-shot or common-receiver gathers instead of first-arrival picking. Both the ray parameter and traveltime information are utilized. The use of Very Fast Simulated Annealing (VFSA) method also allows for easier implementation of the uncertainty analysis. Synthetic and real data benchmark tests demonstrate that this new method is robust, efficient, and accurate. In addition, migrated images of low-fold data or data with limited observation geometry like OBS are often corrupted by migration aliasing. Incorporation of prestack instantaneous-slowness information into the imaging condition can significantly reduce migration artifacts and noise and improve the image quality in areas of poor illumination. Here I combine slowness information with Gaussian beam depth migration and implement a new slowness driven Gaussian beam prestack depth migration. The prestack instantaneous slowness information, denoted by ray parameter gathers p(x,t), is extracted from the original OBS or shot gathers using local slant stacking and subsequent localsemblance analysis. In migration, we propagate both the seismic energy and the principal instantaneous slowness information backward. At a specific image location, the beam summation is localized in the resolution-dependent Fresnel zone where the instantaneousslowness-information-related weights are used to control the beams. The effectiveness of the new method is illustrated using two synthetic data examples: a simple model and a more realistic complicated sub-basalt model. / text

Thesis (Ph.D.)--University of Western Australia, 2007.

Thesis (M.Sc.)--Victoria University of Wellington, 2008. / Includes bibliographical references.