Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2003. / Cataloged from PDF version of thesis. / Includes bibliographical references (page 22). / Geologic deformation in three dimensions can be modeled using finite element analysis. In choosing the elements used to solve a model it is important to consider the accuracy of the solution and the computational intensity. The results for models using six element types and six element side lengths are compared for the accuracy of the displacements calculated by the solution and the number of nodes required, as a proxy for computational intensity. Elements that allow higher order solutions are much more accurate than elements that only allow linear interpolation of the stresses and displacements between nodes; however the number of nodes required is five times greater. Free-form meshes do not significantly improve the performance of tetrahedra for the models tested, but could be accurate enough to model curved problem geometries. Comparisons for other models, such as a thrust fault, can be made using a twodimensional simplification of the three-dimensional problem. If three-dimensional comparisons are required it is important to choose a model that has an analytical solution. / by Teresa Baker. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1991. / Vita. / Includes bibliographical references (p. 169-173). / by Neil McPherson Donahue. / Ph.D.

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. 91-94). / Joint geophysical imaging techniques have the potential to be reliable methods for characterizing geothermal sites and reservoirs while reducing drilling and production risks. In this study, we applied a finite difference tomography method and a double-difference tomography method to image the P- and S-wave velocity structure of the Krafla geothermal reservoir in Northeastern Iceland. We combined over 450 new microearthquakes from a network of borehole seismometers from September 2008 and June-July 2011 with over 800 events recorded by surface networks between 2004 and 2008 that were obtained from the Iceland Geosurvey. Starting event locations were determined from the Joint Hypocenter Determination method. Absolute and relative arrival times were used for the two tomographic inversions to jointly invert for event hypocenter locations and velocity structure. Finally, we compared the final velocity structures with a resistivity model determined from a magnetotelluric inversion. Overall, the earthquakes were located in a tight cluster just south of the IDDP well, concentrated into a horizontal layer centered at 2km depth, and oriented in a NW-SE direction by both tomography methods. The main cluster of earthquake locations is at a saddle point of the resistivity model and near regions of low resistivity. Both methods yielded similar overall velocity models, with a locally low velocity region near the surface and a locally high velocity region moving deeper into the model. We have interpreted a high density intrusion, a gas-filled fracture zone, and a possible partial melt region based on the P-wave, S-wave, and Vp/Vs ratio anomalies in the velocity model. Synthetic modeling of the relationship between the resistivity and velocity models demonstrated the complexities of integrating two data sets with signals of different wavelength and resolution. However, with a better understanding of this relationship and knowledge of physical parameters such as porosity, a better constrained joint-inversion of magentotelluric and seismic data will be possible in the future. / by Beatrice Smith Parker. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1987. / Microfiche copy available in Archives and Science. / Bibliography: leaves 188-196. / by Eduardo P. Olaguer. / Ph.D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, June 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 23-26). / About 70 percent of observed cometary nuclei are bilobate (made up of two masses of material connected by a narrow neck). In contrast, only 10-20 percent of similarly-sized asteroids are contact binaries or bilobate, suggesting that some process unique to comets is responsible for the formation of bilobate shapes. We examine a new mechanism for creating bilobate nuclei in Jupiter-family comets (JFCs), in which sublimative torques acting on a comet during its migration through the Centaur region spin the nucleus up to disruption, after which it may reform in a bilobate shape. We find that JFCs smaller than approximately 100 kilometers in radius should experience enough torque from carbon monoxide and carbon dioxide sublimation over their dynamical evolution through the Centaur region to be restructured into bilobate shapes. This suggests that the observed bilobate distribution of comet shapes could be the result of cometary evolution, rather than a feature of primordial cometary reservoirs. / by Taylor K. Safrit. / S.B.

Thesis (S.M. in Geosystems)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2003. / Includes bibliographical references (leaves 34-36). / The identifiable pattern of the qualitative geomorphologic parameters such as steepness and concavity values that derived from the slope-area analysis of 28 tributaries in the San Gabriel Mountains were used to estimate relative rock uplift rates. The results suggest that the eastern region of the San Gabriel Mountain is controlled by a high rock uplift rate while the western region is controlled by a low rock uplift rate. Furthermore, arrangement of the variations of the steepness and concavity values suggests the presence of an active fault zone between the western and the eastern region of the San Gabriel Mountains. This tectonic zone is responsible for the apparent differentiation in rock uplift rates between the two mountain regions. This conclusion is supported from previous knowledge that suggests faster exhumation and high erosion rates of the East San Gabriel (ESG) block and slower exhumation and lower erosion rates of the Western San Gabriel (WSG) block (Spotila, J., Blythe, A., House, M., Niemi, N., Gregory, B., 2002). Moreover on the technological side of this project, plots of steepness or concavity values derived from analysis of SRTM (30 meter resolution), ASTER (30 meter resolution), USGS (30 meter resolution) and USGS (10 meter resolution) DEMs analysis suggest that USGS DEM-10 meters and SRTM DEM-30 meters are currently the most accurate methods to accurately quantify differential steepness and concavity values for the area of the San Gabriel Mountains in Southern California. Finally, the application of different smoothing options on the plots of slope-drainage area analysis of the tributaries of the San Gabriel Mountains suggests that a 600 meter window size is the optimum size with more reliable information and better noise elimination. / Katerina Dimitris Spyropoulou. / S.M.in Geosystems

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1992. / Includes bibliographical references (leaves 190-195). / by Barry A. Klinger. / Ph.D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2004. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 55-57). / Paleoclimatological investigations into past precipitation and temperature patterns in regions of the tropical Pacific may be the key to resolving scientific disputes about the effects of global warming on the magnitude and frequency of the El Niño/Southern Oscillation (ENSO) phenomenon. Plant lipids identified in the sediment record of lakes in regions of high ENSO activity can act as biomarkers to reconstruct past precipitation patterns by measuring the D/H ratios preserved in these compounds to observe the local climate changes with global temperature variations. Twelve plant species and two sediment samples from in and around El Junco lake catchmernt on Sari Cristobal in the Galapagos Islands were solvent extracted, identified and quantified using gas chromatography arid mass spectrometry. The analysis revealed evidence for significant aquatic and terrestrial vascular plant inputs to lake sediments. High concentrations of unsaturated C₁₆ and C₁₈ fatty acids were found in all plant samples, but these compounds appear to be degraded significantly in the sediment record. n-Alkane distributions suggest a strong hydrocarbon contribution from submerged and floating plants. Additionally, a terrestrial biomarker, fernene, was identified. The information in this study should be a helpful guide for further biomarker identification efforts at the El Junco lake and in other tropical crater lakes. / by Katharine Ricke. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1993. / Includes bibliographical references (p. 45-48). / by Danan Dong. / Ph.D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 24-26). / A large majority of planetary nebulae (PNe) are non-spherical, and many have complex structures; these are unlikely to be created trivially by a single central star. The Binary Hypothesis proposes that the complex morphologies of most non-spherical PNe are caused by interactions between their central stars and companions, with some unknown percentage in close binary systems. In this study, a software pipeline was developed to generate light curves for 140 PNe targets from the Kepler K2 campaign 11 field. Of these 140 targets, 29 appeared to show periodicity in their light curves, all of which had period under two weeks, for a close binary fraction of 21%; furthermore, 25 out of 29 (86%) detected periods were between two hours and five days. The size of this data set (140 PNe) is larger than any previous photometric search for close binary companions of PNe central stars, and the calculated short-period binary fraction is consistent with past photometric searches. These results support the Binary Hypothesis, which in turn helps explain the development of the varied and complex morphologies of PNe. / by Jonathan L. Hurowitz. / S.B.