Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1994. / Includes bibliographical references (leaves 85-87). / by Heidi Suzanne Strader. / M.S.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2002. / Includes bibliographical references (p. 259-296). / Brittle deformation is not distributed uniformly in planetary lithospheres but is instead localized on faults and ductile shear zones. In some regions such as the Central Indian Basin or martian ridged plains, localized shear zones display a characteristic spacing. This pattern can constrain the mechanical structure of the lithosphere if a model that includes the development of localized shear zones and their interaction with the non-localizing levels of the lithosphere is available. I construct such a model by modifying the buckling analysis of a mechanically-stratified lithosphere idealization, by allowing for rheologies that have a tendency to localize. The stability of a heological system against localization is indicated by its effective stress exponent, ne. That quantity must be negative for the material to have a tendency to localize. I show that a material deforming brittly or by frictional sliding has ne < 0. Localization by shear heating or grain size feedback in the ductile field requires significant deviations from non-localized deformation conditions. The buckling analysis idealizes the lithosphere as a series of horizontal layers of different mechanical properties. When this model is subjected to horizontal extension or compression, infinitesimal perturbation of its interfaces grow at a rate that depends on their wavelength. Two superposed instabilities develop if ne < 0 in a layer overlying a non-localizing substratum. One is the classical buckling/necking instability. The other gives rise to regularly-spaced localized shear zones, with a spacing proportional to the thickness of the localizing layer, and dependent on ne. I call that second instability the localization instability. / (cont.) Using the localization instability, the depth to which fault penetrate in the Indian Ocean and in martian ridged plains can be constrained from the ridge spacing. The result are consistent with earthquake data in the Indian Ocean and radiogenic heat production on Mars. It is therefore possible that the localization instability exerts a certain control on the formation of fault patterns in planetary lithospheres. / by Laurent Gilbert Joseph Montési. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2005. / Includes bibliographical references. / This thesis presents the analysis and interpretation of passive seismic data collected in a 20-month monitoring period. The investigation is divided into four studies, each focusing on a different aspect of the seismic data to infer the reservoir properties. First, I applied three different methods (the iterative linearized, nonlinear grid-search, and double-difference methods) to relocate 405 microearthquakes that occurred between October 1999 and June 2001 in a producing field in Oman. A numerical technique is applied to "collapse" the relocated hypocenters and to find the simplest structural interpretation consistent with the data. Comparing the methods, the applicability of waveform correlation methods such as the double-difference in this case is limited by the relatively large number of events with dissimilar waveforms. Unlike the iterative linearized method, the nonlinear grid-search method gives the best results with the smallest average rms error of the absolute locations because it avoids the local minimum problem. / (cont.) The relocated hypocenters clearly delineate nearly vertical, northeast-southwest striking faults near the crest of the field, which is consistent with the graben fault system mapped by surface geologic surveys and reflection seismic interpretations. I also performed statistical tests to estimate location errors, and found that the station geometry is the major factor that limits the accuracy of focal depths. Secondly, this thesis presents a non-linear wavelet-based approach to linear waveform inversion of high-frequency seismograms for the estimation of a point source mechanism and its time function. For earthquake mechanism inversions, it is important to stabilize the problem by reducing the number of parameters to be determined. Commonly, overlapping isosceles triangles or boxcar functions are used for the parameterization of the moment tensor rate functions (MTRFs). Here, I develop a wavelet-based strategy that allows us to construct an adaptive, problem-dependent parameterization for the MTRFs employing fractional spline wavelets. Synthetic results demonstrate that the adaptive parameterization improves the numerical approximation to the model space and therefore, allows more accurate estimations of the MTRFs. / (cont.) The waveform inversion is performed in the wavelet domain and leads to a multiresolution sparse matrix representation of the inverse problem. At each resolution level a regularized least-squares solution is obtained using the conjugate gradient method. The wavelet-based waveform inversion method has been applied successfully in three real- data examples: the April 22, 2002 Au Sable Forks, New York earthquake, the September 3, 2002 Yorba Linda, California earthquakes, and 11 M>1 microearthquakes in a producing field in Oman. In the Oman field, the dominant styles of focal mechanism are left-lateral strike-slip for events with focal depths less than 1.5 km, and dip-slip along an obliquely trending fault for those with focal depths greater than 2.0 km. Thirdly, the covariance matrix method of shear-wave splitting analysis is presented. Different from conventional methods that usually analyze only two horizontal components, this method processes all three components of the seismogram simultaneously, allowing not only orientation but also dip information of fractures to be resolved. Synthetic test results show that this method is stable even for high noise level. / (cont.) The method is applied to the Oman microearthquake records that display distinctive shear-wave splitting and polarization directions. From the polarizations, I estimate the predominant subsurface fracture directions and dipping angles. From the time delays of the split wave I determine the fracture density distributions in the reservoir. Finally, I examine the spatio-temporal characteristics of the microseismicity in the producing reservoir. The frequency-magnitude distribution measured by the b-value is determined using the maximum likelihood method. I found that b-values are higher for events below the deeper Shuaiba oil reservoir than those above. Also, the feasibility of monitoring the temporal change of b-values is demonstrated. The analysis of production and injection well data shows that seismicity event rates in the field all strongly correlated with gas production from the shallower Natih Formation. Microseismicity, focal mechanisms, GPS analysis, and production / injection well data all suggest the NE- SW bounding graben fault system responds elastically to the gas-production-induced stresses. Normal faulting is enhanced in the reservoirs by the compaction related stresses acting on the graben fault system. / by Edmond Kin-Man Sze. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1989. / Lindgren second copy is bound in one vol. / Chapter 3 co-authored by Matthew T. Heizler; chapter 4 co-authored by J. Douglas Walker. 4 folded leaves inserted in pocket of v. 1. / Includes bibliographical references. / by James Howard Knapp. / Ph.D.

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 (p. 317-323). / The systematic design of experiments to optimally query physical systems through manipulation of the data acquisition strategy is termed optimal experimental design (OED). This dissertation introduces the state-of-the-art in OED theory and presents a new design methodology, which is demonstrated by application to DC resistivity problems. The primary goal is to minimize inversion model errors and uncertainties, where the inversion is approached via nonlinear least squares with L1 smoothness constraints. An equally important goal is to find ways to expedite experimental design to make it practical for a wider variety of surveying situations than is currently possible.A fast, sequential ED strategy is introduced that designs surveys accumulatively by an efficient method that maximizes the determinant of the Jacobian matrix. An analysis of electrode geometries for multielectrode data acquisition systems reveals that experiment-space can be usefully decimated by using special subsets of observations, reducing design CPU times. Several techniques for decimating model-space are also considered that reduce design times.A law of diminishing returns is observed; compact, information-dense designed surveys produce smaller model errors than comparably sized random and standard surveys, but as the number of observations increases the utility of designing surveys diminishes. Hence, the prime advantage of OED is its ability to generate small, high-quality surveys whose data are superior for inversion.Designed experiments are examined in a Monte Carlo framework, compared with standard and random experiments on 1D, 2D and borehole DC resistivity problems in both noiseless and noisy data scenarios and for homogeneous and heterogeneous earth models. Adaptive methods are also investigated, where surveys are specifically tailored to a heterogeneous target in real time or in a two-stage process. / (cont) The main contributions this thesis makes to geophysical inverse theory are: 1) a fast method of OED that minimizes a measure of total parameter uncertainty; 2) novel techniques of experiment-space and model-space decimation that expedite design times; 3) new methods of adaptive OED that tailor surveys to specific targets; and 4) though the OED method is demonstrated on geoelectrical problems, it can be applied to any inverse problem where the user controls data acquisition. / by Darrell A. Coles. / Ph.D.

Thesis: S.B. in Planetary Science and Astronomy, Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2003. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 25-26). / Four interplanetary shock waves and disturbances are analyzed. Data recorded by multiple spacecraft are compared in order to determine how the speed of these events is modified when they cross Earth's bow shock into the magnetosheath. To accomplish this, it was necessary to find shocks that were seen by spacecraft both in the solar wind and inside the magnetosheath. Using a velocity coplanarity and a Rankine-Hugoniot methods of shock normal analysis, the speeds of these events in the solar wind were calculated. The time of their arrival at a spacecraft in the magnetosheath was determined. The predicted arrival time, assuming a constant shock speed from the spacecraft in the solar wind to the spacecraft in the magnetosheath is then compared to the actual arrival time. The resulting data support the conclusion that there is no change in the speed of the shock as it propagates through the magnetosheath. / by Aletta M. J. Wallace. / S.B. in Planetary Science and Astronomy

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2008. / Cataloged from PDF version of thesis. / Includes bibliographical references (page 24). / In this thesis, spontaneous tropical cyclogenesis occurring in a cloud-resolving numerical model is studied. The model environment is one of radiative convective-equilibrium on an f-plane with doubly periodic boundary conditions and constant sea surface temperature. While a variety of initial conditions may exhibit spontaneous tropical cyclogenesis, this study focuses on one. Using assumptions of axisymmetry for the growing disturbance and focusing on the large scale processes, fields were created for a number of thermodynamic variables along constant height surfaces and as azimuthal means plotted against height. The tropical cyclone is hypothesized to develop in three steps. First, convective aggregation creates regions of high moist static energy, and regions of cold dry air. Importantly, a deep moist column is created which provides a perfect environment the developing storm. In the second step, mid-level cyclone intensification, a mid-level cold core cyclone develops in the deep moist region, and benefits from moist static energy and potential vorticity fluxes from the upper troposphere. Exhibiting anticyclonic convergent flow, the upper troposphere is an unlikely source for the mid-level disturbance, while convective downdrafts and divergent surface flow hinder energy transport from the ocean to the growing system. In fact, a cold surface anticyclone exists near the center for much of the second step. It is not until potential vorticity anomalies advect down to the surface that the final step, low-level cyclone intensification, creates a classical hurricane structure. Potential vorticity advection stimulates cyclonic flow at the surface, extinguishing the surface anticyclone, and thereby linking the mid-level disturbance to the oceanic energy source. While like some cold core cyclones previously studied, the anticyclone as an energy source is unique to this spontaneous case. / by Paul M. Hoffman. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 51-55). / Recently acquired altimetry data from laser altimeters are used to assess the morphometry of impact craters. Data acquired by the Mercury Laser Altimeter on the MESSENGER spacecraft are used to measure the depths and diameters of 537 craters at the high northern latitudes on Mercury, including 42 polar-deposit-hosting craters (PDCs) which host material that is bright to earth-based radar observations. A comparative analysis suggests that the radar-bright material forms a thin (< 20 m) layer emplaced preferentially in comparatively young craters, contradicting an earlier morphometric study that indicated that PDCs contained a thick layer of water ice and dust. Topographic datasets from the lunar surface, collected by the Lunar Orbiter Laser Altimeter onboard the LRO spacecraft, are also used to evaluate the morphometry of 1,356 lunar craters. We study the morphologic change between the simple and complex crater regime, a manifestation of the transition between gravity-dominated and strength-dominated impact-forming processes, on the Moon and Mercury. The Moons transition diameter is near 16 km, in line with previous studies, while Mercurys is near 8 km, 2 km smaller than previously determined. The onset of gravity-dominated mechanisms scales inversely with gravity, which explains why Mercurys transition diameter is approximately half of the Moons. / by Matthieu Jean Talpe. / S.M.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2008. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 52-56). / Twelve bedrock samples were collected from Ticino, Switzerland and Northern Italy for thermochronological studies using the (U-Th)/He technique on zircon and apatite and fission track on subset of zircons. Nine samples were collected from the Lepontine Dome, north of the Insubric Line, six of which were in an approximate vertical, or elevation, transect. Three samples were also taken in a vertical transect from the Southern Alps, south of the Insubric Line. (U-Th)/He Zircon dates from north of the Insubric line ranged from 7 to 14 Ma, and indicate an approximate exhumation rate for the region of 1000 m/Ma. U-Th/He zircon dates from south of the Insubric Line ranged from 100 to 180 Ma, with one reliable apatite date of 23 Ma. These data lead to an approximate exhumation rate of 20 m/Ma in the south with rates increasing to about 150 m/Ma since 23 Ma. Thus very different exhumation histories can be inferred north and south of the Insubric Line, with the north side showing much younger dates and a higher exhumation rate related to continued orogenic activity, whereas to the south, there are lower rates and older dates indicating little to no orogenic activity until ca 23 Ma. / by Jessica R. Stanley. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2013. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (p. 269-304). / The endeavor to characterize terrestrial exoplanets warrants the study of chemistry in their atmospheres. Here I present a comprehensive one-dimensional photochemistry-thermochemistry model developed from the ground up for terrestrial exoplanet atmospheres. With modern numerical algorithms, the model has desirable features for exoplanet exploration, notably the capacity to treat both thin and thick atmospheres ranging from reducing to oxidizing, and to find steady-state solutions starting from any reasonable initial conditions. These features make the model the first photochemistry-thermochemistry model applicable for non-hydrogen-dominated thick atmospheres on terrestrial exoplanets. Using the photochemistry model, I explore the compositions of thin atmospheres on terrestrial exoplanets controlled by surface emission and deposition of gases. Highlights of my findings are: (1) oxygen and ozone may build up in 1-bar CO2 atmospheres to levels that have conventionally been accepted as unique signatures of life, if there is no surface emission of reducing gases; (2) volcanic carbon compounds (CH4 and CO2) are likely to be abundant in terrestrial exoplanet atmospheres; but volcanic sulfur compounds (H2S and SO2) are chemically short-lived and therefore cannot accumulate in virtually any types of terrestrial exoplanet atmospheres. Also using the photochemistry model, I explore the ranges of molecular compositions of thick atmospheres on terrestrial exoplanets. I find that carbon has to be in the form of CO2 in a H2-depleted water-dominated atmosphere, and that the preferred loss of light elements from an oxygen-poor and carbon-rich atmosphere leads to formation of unsaturated hydrocarbons (C2H2 and C2H4). These results imply that chemical stability has to be taken into account when interpreting the spectrum of a super Earth/mini Neptune like GJ 1214b. Another intriguing category of terrestrial exoplanets is bare-rock exoplanets. I present the first theoretical framework to compute disk-integrated spectrum from a bare-rock exoplanet, taking into account the reflectivity and emissivity of solid minerals on the surface. I find that silicate surfaces lead to prominent spectral features in the 8 - 13 [mu]m range, detectable by mid-infrared spectroscopy using transit. Therefore transit spectroscopy is an independent method to confirm the rocky nature of an exoplanet. / by Renyu Hu. / Ph.D.