Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1995. / Includes bibliographical references (p. 122-126). / by Christopher R. Weidman. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 123-132). / In this dissertation, I investigate the assembly and evolution of the Archean cratonic lithosphere by using two complementary seismological methods to image the lithospheric structure of the Slave craton in Canada. First, I perform surface wave tomographic inversions to constrain the depth dependence of Rayleigh wave phase velocity, shear wave velocity, and azimuthal anisotropy of the Slave cratonic lithosphere. The tomographic images reveal high shear wave velocities associated with a particularly depleted, cold, and unperturbed Archean cratonic lithosphere. Furthermore, the inversions reveal distinct anisotropic domains in the crust, the lithospheric mantle, and the sub-lithospheric mantle. These results reflect the evolutionary history of the cratonic lithosphere. Secondly, I image seismic discontinuities in the lithosphere using receiver-function analysis of converted P-to-S waves. The resulting seismic profile shows a pronounced low velocity discontinuity at -100 km depth beneath the central Slave craton. This seismic discontinuity shows striking spatial correlation with both an electrical conductive anomaly derived from magnetotelluric sounding, as well as a petrologically-defined ultra-depleted layer. The synthesis of coincident seismic, electrical, and petrological evidence supports that this geophysical and petrological boundary represents a compositional interface marked by alteration minerals. I suggest that this mineralization resulted from relict metasomatism associated with an Archean subduction event, which played an important role in the assembly of the Slave craton. Finally, to improve the efficiency and automation of receiver function calculation and data preprocessing workflow, I develop an application of an array-conditioned deconvolution technique for effectively processing large amounts of seismic array data. I demonstrate that this technique is readily applicable to teleseismic array data. This technique is especially effective in turning noisy traces from earthquakes with smaller magnitudes into usable data. / by Chin-Wu Chen. / Ph.D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 31-32). / QX Pup is a known Mira variable at the core of the Rotten Egg Nebula that has not been studied in detail since its discovery in 1983. In this study, four years of photometric data in V and I and two years of photometric data in R and B are analyzed. A period of T = 535.4 ± 8 days, and a magnitude drop of [Delta]mI , = 2.2 ± 0.69 are measured in I, and and phase shifts between the the other three filters and I are determined to be [o]R = 6 ± 40 days, [o]B = 66 ± 64 days, #, [o]v = 16 ± 86 days. These results are used to speculate about the possibility of a light-echo off the Rotten Egg Nebula and the conditions on Earth-like planets around Mira variables. / by Kristin L. Berry. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1999. / Includes bibliographical references (leaves 60-63). / Detailed understanding of the heterogeneities and complexity of reservoir architecture and flow properties are crucial to development and exploitation of commercial hydrocarbon reservoirs. Thus, reservoir characterization and simulation studies are done on a continuous basis during the life of a field from initial exploration through appraisal, development and eventual abandonment. A key component of these studies is the knowledge of the reservoir permeability across the field. However, permeability is only measured directly at the pore scale from core, and since cores are rarely taken in a significant percentage of the wells in a field, estimation methods are commonly used to predict the permeability in wells without core data. These methods have included empirical and statistical approaches, as well as the emerging pattern recognition techniques. The accuracy of most methods are greatly enhanced when the reservoir is subdivided into units with common flow properties. In this thesis, a case study is carried out in the Benin River/Gbokoda field in Nigeria, with the aim of developing from existing tools, a facies based, simple to use, accurate and readily available technique to predict permeability in fields where there is at least one well that has core data for calibration of the reservoir properties and facies. The use of the facies data to constrain the prediction greatly improved the match between the predicted and the actual. The reservoir is subdivided into depositional groupings based on lithofacies and facies association, flow properties, and ease of recognition on wireline logs. Linear equations were developed from multiple regression of wire line log data to predict this groupings. The predicted groupings and the wireline Jog data were used in a multiple regression to develop another set of linear equations to predict permeability in each grouping. The equations produced were applied to a test well that had core data but was not used in the study. The predicted groupings and permeability from the test well was in very close agreement with the original data. The equations are next applied to other wells in the field. / by Clement Olajide Aina. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, 1987. / Bibliography: leaves 41-47. / by George Micah Connor Blumberg. / M.S.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1999. / Includes bibliographical references (leaves 232-236). / Ground penetrating radar (GPR) surveys are performed to determine geologic structure and to assist in the characterization and eventual modeling of ground water flow beneath the Well-H region of the Aberjona River in Woburn, Massachusetts. Even though cone penetrometer and coring studies provide point source "ground truth" data about the stratigraphy, soil chemistry, and composition of the first seven meters of peat, sand and silt they are time-consuming and labor intensive. The advantage of GPR is its ability to extend point-source ground truth information into two and three dimensions. This dissertation provides an accurate geologic model of one section of the Aberjona wetland by improving the state of three-dimensional GPR imaging. Data fusion, target implantation, and a novel 3-D migration technique are combined to render the subsurface volume accurately to resolutions of about 30 centimeters in all directions. The technique was tested using various synthetically generated models as well as carefully constructed test pits to verify its accuracy and estimate error. For our surveys in the wetland, we verify the accuracy of our method using the large database of "ground truth" information about subsurface structure and soil properties. We use this information along with data collected for this project to assemble what 3-D geological information we can. For example, direct measurements of soil bulk properties are made at various depths in several locations. Borehole conductivity surveys not only confirm core sample measurements, but also give deep conductivity information not otherwise available. Cone penetrometer surveys provide high vertical resolution to map stratigraphic variation. A 3-D resistivity survey provides general information about the conductivity of the site. In addition to ground truth measurements, several different types of radar surveys were employed to estimate soil electrical properties. A new method of Vertical Radar Profiling (VRP) was developed to provide velocity information at different locations and various depths throughout the wetland. Morphing methods were applied as an interpolation tool for surveys with broadly spaced profiles. A fast three dimensional migration algorithm was developed specifically for GPR imaging that incorporates layered velocity information and soil electrical conductivity. Ultimately, this technique is shown to offer a means of mapping larger regions of wetland stratigraphy more accurately than was currently feasible. / by David Bishop Cist. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1999. / Includes bibliographical references (leaves 85-90). / In this research, the global annual flux of inorganic carbon into groundwater was calculated to be 4.4 GtC/y, with a lower bound of 1.4 GtC/y and an upper bound of 27.5 GtC/y. Starting with 44 soil PCO2 measurements, the dissolved inorganic carbon (DIC) of the groundwater was determined by equilibrium equations for the carbonate system. The calculated DIC was then multiplied by the groundwater recharge to determine the annual carbon flux per area. These PCO2 estimates were assigned to specific bio-temperatures and precipitations according to the Holdridge life-zone classification system, and regressions between PCO2, biotemperature, and precipitation were used to provide estimates for regions of the world that lacked PCO2 measurements. The fluxes were mapped on a generalized Holdridge life-zone map, and the total flux for each life-zone was found by multiplying the calculated flux by the area in each life-zone. While there was a wide range in the error, the calculations in this study strongly suggest that the flux of carbon into groundwater is comparable to many of the major fluxes that have been tabulated for the carbon cycle. The large flux that was calculated in this study was due to the high PCO2 that is common in soils. The elevated PCO2 levels are due to the decomposition of organic matter in soils, and the absorption of oxygen by plant roots. After the groundwater enters into rivers, it is possible that large amounts of CO2 is released from the surface of rives, as the carbon-rich waters re-equilibrate with the low atmospheric PCO2- / by Toby Jonathan Kessler. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1999. / Includes bibliographical references (leaves 75-76). / We propose a method to study natural topography by means of local transform. A nonlinear local transform Alc[h(x)] of the elevation field h(x) is used to determine a director field of anisotropy a(x). The director field is directly related to local small-scale channel-like features. From study of the correlations of these with large-scale structure of drainage basins, characteristic coupling length scales are found which indicate an important breaking of scale invariance. We also show that these length scales are related to the average sizes of the individual drainage basins. Our study demonstrates one way in which landscape patterns of unknown origin may be quantitatively analyzed to determine the kind of mechanisms that have eroded them. / by Kelvin Ka Wing Chan. / S.M.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1999. / Includes bibliographical references (p. 231-236). / The ice sheets of the last glacial maximum (about 21 thousand years ago) covered a significant fraction of the high latitude land mass, reached up to 3km in height, and had length scales of thousands of kilometers. They represented significant obstacles to the westerly flow of the atmosphere. As the atmospheric flow is forced to deviate around such topographic features, stationary waves-large scale standing patterns in the winds and temperatures-are established within the atmosphere. The largest of the ice sheets, the Laurentide (over North America), was approximately equal in both horizontal extent and height to the Tibetan Plateau, which is known to be a significant contributor to the stationary wave pattern in today's climate. As the ice sheet evolves, the patterns of temperature and winds due to the stationary wave change, and therefore the distribution of precipitation and ablation (melting) is altered over the ice sheet. These altered distributions will, in turn, change the shape of the ice sheet itself, given sufficient time over which to act. It is not possible to integrate full dynamical climate models for the long time scales appropriate to ice sheet dynamics (> 103yrs). Previous studies have typically either used general circulation models (GCMs) for 'snapshot' climate simulations with prescribed ice age insolation and boundary conditions, or used long integrations of energy balance models (EBMs), which do not account for atmospheric dynamics. We aim for an intermediate approach-including some of the important dynamical features of the climate within a framework which is nonetheless simple enough to do long term calculations with. In the most reduced approach, an ice sheet is treated as a perfectly plastic material, lying in the north-south direction. Simple representations of ablation and accumulation show that in equilibrium the southern margin of the ice sheet is tied quite strongly to a particular annually averaged isotherm. For a topographically forced stationary wave of reasonable amplitude, this implies that the potential effect of the stationary wave is to double the extent of the ice sheet over and above that which would exist without the stationary wave. The effects explored above in the rather restrictive two-dimensional approach are further studied using a fully three-dimensional ice sheet model coupled to a #-plane channel stationary wave model, which is quasi-geostrophic, steady state, and linear. The two components of the model interact via the accumulation and ablation parameterizations which are, of necessity, very simplified representations. The ablation parameterization is the positive degree day model which has been used to model the modern ice sheets. The accumulation parameterization places particular emphasis on the topographic influence on precipitation. This more sophisticated approach shows that, in an idealized rectangular geometry, the height, shape, and orientation of the ice sheet are all dependent on the stationary wave that it creates. The fundamental competing balance is between the enhanced precipitation on the windward slopes, and the cold temperatures due to the atmospheric flow in the lee of the ice sheet, which allows the ice there to flow to lower latitudes than it otherwise could. When the stationary wave model is applied to a reconstruction of the topography at the last glacial maximum, the results suggest that the stationary wave patterns due to Tibet and the Rockies may have played a role in preconditioning different regions for ice sheet initiation. Once established, the Laurentide ice sheet exerted a strong influence on the climate over the Fennoscandian ice sheet (over northern Europe) due to the downstream propagation of the stationary wave it created. Simulations with the ice sheet model over North America show that the atmospheric stationary wave creates a tendency for the ice sheet to have the shape of the Laurentude at the last glacial maximum. However, the simplicity of the model, together with the lack of knowledge about the glacial atmosphere, means it is not possible to conclude that the interaction was sufficient to create the observed configuration. / by Gerard Hugh Roe. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1999. / Includes bibliographical references (p. 224-230). / The properties of Saturn's upper atmosphere are not well-known despite several spacecraft flybys. However, the region of 1-100 [mu]bar can be studied in detail by observing stellar occultations -- when the planet passes in front of a star -- from ground-based or Earth-orbiting telescopes. We use data from five such occultations: three observed in 1995 by the Faint Object Spectrograph (FOS) on the Hubble Space Telescope (HST), one observed in 1996 at the NASA Infrared Telescope Facility (IRTF) and one in 1989 observed by a different instrument at the IRTF. The data span latitudes from 52° south to 75 ° north. We fit isothermal models to each data set and also perform numerical inversions. These analyses show that temperatures in the 1-10 [mu]bar range can vary significantly as a function of season and latitude, ranging from 121 to 160 K, in accordance with radiative transfer models for the atmosphere. We also search for evidence of gravity wave saturation in Saturn's upper atmosphere, as seen in other planetary atmospheres, by analyzing the power spectra of temperature and density data and by studying the temperature lapse rate in the atmosphere. Our analysis is consistent with saturated gravity waves for all data sets, although gravity wave saturation is not the sole explanation for the spectra. We take advantage of the wavelength-resolved HST FOS data to study the composition of Saturn's upper atmosphere. We measured the difference in feature times for data taken at two wavelengths, and use the different refractivities of hydrogen and helium, as a function of wavelength to compute the relative amounts of the two elements in the planet's atmosphere. We find that the helium mass fraction is 0.26 ± 0.10, higher than that found using Voyager data, but marginally consistent with theoretical models for the evolution of Saturn's atmosphere, although the large error bars on the results make a definitive conclusion problematic. / by Jeffrey Alan Foust. / Ph.D.