Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1996. / Includes bibliographical references (p. 193-199). / Natalie Marie Mahowald. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 40-42). / We use a 2-D finite difference method to numerically calculate the seismic response of a single finite fracture in a homogeneous media. In our experiments, we use a point explosive source and ignore the free surface effect, so the fracture scattering wave field contains two parts: P-to-P scattering and P-to-S scattering. We vary the fracture compliance within a range considered appropriate for field observations, 10-12 m/Pa to 10-9 m/Pa, and investigate the variation of the scattering pattern of a single fracture as a function of normal and tangential fracture compliance. We show that P-to-P and P-to-S fracture scattering patterns are sensitive to the ratio of normal to tangential fracture compliance and different incident angle, while radiation pattern amplitudes scale as the square of the compliance. We find that, for a vertical fracture system, if the source is located at the surface, most of the energy scattered by a fracture propagates downwards, specifically, the P-to-P scattering energy propagates down and forward while the P-to-S scattering energy propagates down and backward. Therefore, most of the fracture scattered waves observed on the surface are, first scattered by fractures, and then reflected back to the surface by reflectors below the fracture zone, so the fracture scattered waves have complex ray paths and are contaminated by the reflectivity of matrix reflectors. / by Xinding Fang. / S.M.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2000. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 21-22). / Under the auspices of NASA's Global Tropospheric Experiment (GTE), the Pacific Exploratory Missions (PEM) have collected numerous air samples of many regions of the troposphere. Data from PEM-West B (February 7 to March 15, 1994), and PEM-Tropics A (August 15 to October 5, 1996) have been used here to study non-methane hydrocarbon (NMHC) ratios and to compare pollution transport by large scale convection and subsidence, as well as horizontal transport across the Pacific. For PEM-Tropics A, 7 cases are studied, each involving different aspects of transport. Persistent circulation features in the South Pacific played a significant role in NIMHC ratio distribution and processing. For PEM-West B, sources of a large pollution region are studied and compared to equatorial transport. NMHC ratios were found to be useful tracers of pollution distribution through the troposphere. The contrasts of these ratios across relatively small distances, particularly on either side of the South Pacific Convergence Zone in PEM-Tropics A, suggest that convection shapes pollution transport and distribution, particularly in the South Pacific. / This work was supported by the NASA GTE program under grant NAG1-1758 and NAG1-2173 / by Christopher Chay Casso. / S.B.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1994. / Includes bibliographical references (p. [193]-[198]). / by Kyle William Blasch. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2008. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references. / In the lithosphere, strain is frequently accommodated along localized shear zones, the rheology of which are inextricably linked to their microstructural characteristics. Shear zones in orogenic belts frequently form in calcite-rich lithologies due to the relatively low strength of these rocks, especially when compared to quartz- and feldspar-rich lithologies. This dissertation addresses the kinetics of microstructural evolution during deformation of calcite-rich rocks, and the coupling between the rheological properties of deforming rocks and such microstructural characteristics as grain size and crystallographic preferred orientation (CPO) by combining laboratory studies with field based observations. In Chapter 2, a scaling relationship for recrystallized grain size is derived based on a balance between the rate that mechanical work is done during deformation and the rate that this energy can be dissipated. This suggests that recrystallized grain size reflects the product of stress and strain rate rather than stress alone. When this scaling relationship is applied to measured calcite grain sizes from the Morcles nappe, in the Swiss Helveitc Alps, where the microstructure is unaffected by second phases, the geologically estimated regional strain rates are successfully reproduced, and when it is applied to samples collected along a transect perpendicular to the thrust contact, the results suggest strain became progressively localized (Chapter 3). This calculation is consistent with the increased CPO intensity which is observed in the finest grained mylonites closest to the thrust contact. In Chapter 4, laboratory deformation experiments are used gain insight into the kinetics of microstructural evolution in calcite-rich rocks. The grain size evolution rates measured in experiments correlate well with the product of the measured stresses and strain rates, consistent with the scaling relationship presented in Chapter 2. These experiments also suggest that, with increasing strain, strain rates will increase at constant stress, and there is a correlation between this weakening and the formation and intensification of CPO, consistent with the observations in the Morcles nappe. Rocks are seldom composed of a single mineral phase. / (cont.) The influence of rigid second phases on the strength, CPO, and grain size of deforming marbles is investigated through a combination of hydrostatic, compression, and torsion experiments performed in the laboratory, which are presented in Chapters 5&6. Both the volume fraction and geometry of rigid second phases have a dramatic effect on the mechanical strength, the CPO, and the grain size. In samples deformed to high strains in torsion, where the recrystallized grain size resulting from deformation is finer than the grain size due to pinning of grain boundaries by the rigid inclusions, the scaling relationship derived in Chapter 2 successfully predicts the measured recrystallized grain size. Thus, this scaling relationship is consistent with both grain size evolution rates and stabilized grain sizes measured in the laboratory, and with field constraints on the strain rates in the Morcles nappe. / by Nicholas James Austin. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2001. / "February 2001." / Includes bibliographical references (leaves 17-19). / Common methods of extracting representations of drainage networks from raster digital elevation models for hydrological and geomorphological applications are similar to a class of image processing methods known as grayscale watershed algorithms. These algorithms partition a field of scalar values into connected regions based on a local minimum associated with each region. A related class of image processing algorithms, known as 2-dimensional skeletonization algorithms, reduce a planar shape to a one-dimensional, connected, graph-like structure, called a skeleton, that maintains significant information about the properties of the original shape. The morphological similarity between the skeleton of a region and a drainage network suggest that skeletonization algorithms might be used to relate basin shape to the drainage network within the basin. This idea was examined by applying two 2-dimensional skeletonization algorithms to two drainage basin boundary shapes extracted from digital elevation models to attempt to predict stream channel locations within the basin. The skeletons computed for the two basins studied did not predict the location of principal channels in the interiors of the basins studied. This is due, at least in part, to the fact that these two dimensional algorithms only consider symmetry with respect to plan view basin shape, with no consideration made of relative elevations along basin boundaries or position of the boundary points with respect to the basin outlet. In convex outward salients of the upper reaches of the two basins studied, the position and planform of computed skeletons agree reasonably well with the upper reaches of drainage networks derived from the digital elevation model. This observation suggests a relationship between basin boundary shape and the location and form of the channel network, at least in the neighborhood of the boundary in upper portions of the basins. A brief review of recent results from computational geometry and image analysis suggest several possible methods of extending this analysis to incorporate relative elevation along the boundary and orientation of the boundary with respect to the basin outlet, and possibly resolving this question. / by Robert J. Fleming, Jr. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2002. / Includes bibliographical references (leaves 67-68). / High precision GPS receiver can yield position measurements within millimeter level accuracy. This accuracy provides an opportunity to observe subtle changes such as crustal movements. In addition,it allows the monitoring of large structures such as dams for safety reason. A GPS system was installed at Pacoima Dam in order to monitor potential instability. The GPS system consists of 2 receivers, DAMI and DAM2, which are part of GPS network in Southern California. The displacement derived from the GPS receivers indicated that the dam's arch moves periodically with an annual period. Because of the annual period of the time series, we investigated if the movement of the dam arch could be due to thermoelastic deformation. An estimation of the dam arch displacement change based on thermoelastic deformation theory is derived. To analyze the observables, we performed spectral analysis between the GPS displacements and the temperature variation. The spectral analysis results is in agreement with the magnitude derived from thermoelasticity theory. The results show that Pacoima Dam's displacement is consistent with thermoelastic deformation. The water loading however may also have contribution to the movement of the dam. / by Monchaya Piboon. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1993. / Includes bibliographical references (leaves 135-141). / by Nathalie Anne Daniell Waser. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1985. / Microfiche copy available in Archives and Science. / Bibliography: leaves 222-235. / by Walter Roger Buck. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1987. / Microfiche copy available in Archives and Science. / Bibliography: leaves 65-66. / by David J. Lineman. / M.S.