Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2006. / Includes bibliographical references (p. 85-89). / Alkenone-based estimates of sea surface temperature (SST) in the northwest Atlantic during the last 10,000 years are presented and used to assess scenarios for Holocene climate variability. Alkenone concentration and unsaturation records are presented from cores KNR140-39GGC, KNR140-51GGC, MD95-2028, MD95-2031, and MD95-2025 from the Blake Ridge (320N), Carolina Slope (330N), Fogo Seamount (42°N), Narwhal (440N), and Orphan Basin (500N) respectively. The southernmost core, from the Blake Ridge, indicates very little temperature variation over the Holocene. Somewhat inshore and to the north of that location, the Carolina Slope record shows a slight cooling trend of about 1.50C over the past 5,000 years, which is interrupted by a brief but sudden drop of about 1C between 3,000 and 2,000 years before present. Lack of age control for the core from Fogo Seamount prevents any conclusions about the time frame of alkenone variation at that location. At the Narwhal site, which is not far from the Laurentian fan, a strong and consistent cooling of 9C is the most recent pattern of variation. Alkenone concentrations from the Orphan Basin were not sufficient for reliable measurement of a Holocene temperature trend. / (cont.) The general pattern of strong cooling in the northern slope water region and very modest cooling south of Cape Hatteras, where the Gulf Stream separates from the coastline and heads out. to sea, may suggest a shift in mean Gulf Stream path as a possible culprit for the temperature record seen at the Narwhal site. However, changes of incoming solar radiation or seasonality of alkenone production over the Holocene provide alternative mechanisms for alkenone temperature variation. / by Jessie M. Kneeland. / S.M.

Thesis: S.M. in Geophysics, Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 112-117). / Aquifer storage and recovery (ASR) of treated wastewater is a viable sustainable water management option for Kuwait. A geophysical survey to characterize the target aquifer in the Dammam Formation was conducted to obtain one-dimensional (1D) resistivity using the D.C. resistivity (DCR) and transient electromagnetic (TEM) methods. For DCR, we implement a systematic approach to obtain a 1 D vertical profile using fixed-thickness and variable-thickness layer inversion techniques in succession. The optimal model has 6 layers above the half-space depth of 101 m, consisting of 3 surface layers down to 15 m depth and 3 intermediate layers, which correspond to the formations of the Kuwait Group overlying the Dammam Formation. Anomalies in the data which cannot be attributed to noise or error are not adequately fit by the best set of ID models. The possibility that lateral heterogeneity explains the variation in the data is explored using approximate 2D resistivity inversion. A comparison of the 1D vertical profile obtained from the approximate 2D image with the 1D layered model indicates that, in our case, 1D analysis provides a sufficient picture of the subsurface despite the evidence of possible lateral heterogeneities in the subsurface. Such heterogeneity is explained by the occurrence of gatch (caliche) in the Fars and Ghar formations of the Kuwait Group. The comparison between DCR and TEM indicates that the TEM data is not sensitive to a relatively resistive layer that is resolved by the 1D DCR inversion, or to the resistive heterogeneities that are indicated in the DCR data with respect to the best fit. We obtain the top of the Dammam formation - or the aquitard on top of the Dammam - as the model half-space depth at approximately 100 m below the surface in both data sets. / by Nasruddin Abbas Nazerali. / S.M. in Geophysics

Thesis: S.M. in Planetary Sciences, Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 65-70). / Sample retrieval from extraterrestrial bodies and in situ resource utilization (ISRU) activities have been identified as some of the most important scientific endeavors of the coming decade. With the failure of Rosetta's Philae lander to penetrate the surface of comet 67P and obtain a sample due to the high compressive strength of the surface, it is becoming obvious that knowledge of the mechanical properties of materials that might be encountered in such environments and under such conditions is critical to future mission success. Two comet/asteroid analogs (Indiana limestone and Bishop tuff), selected based on their contrasting mechanical properties and porosities, were tested under constant displacement to failure (in most cases) at extraterrestrial conditions of cryogenic temperatures (295 K down to 77 K) and light confining pressures (1 to 5 MPa). The compressive strength of both materials was determined under varied conditions of saturation, from oven-dried (~0% water content) to fully saturated, and both brittle and ductile behavior was observed. The saturated limestone increased in strength from -30 MPa (at 295 K) to >200 MPa (at 77 K), while the Bishop tuff increased in strength from 13 MPa at 295 K to 165 MPa at 150 K. Additional experiments demonstrated that thermal cycling reduces the compressive strength of limestone, while an increase in confining pressure from 5 MPa to 30 MPa at 200 K significantly increases the strength (from 62 MPa to 85 MPa respectively) of saturated tuff. The results of this study will be useful to future sample retrieval missions or ISRU maneuvers. The large increase in compressive strength of these saturated materials at cryogenic temperatures means that future missions will need to prepare technology that has the energetic and mechanical capability to penetrate very hard substrates as they are likely to encounter. / by Jared William Graham Atkinson. / S.M. in Planetary Sciences

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1995. / Includes bibliographical references (leaves 84-88). / by Giuseppe A. Sena. / M.S.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, February 2001. / Includes bibliographical references. / The eastern margin of the Tibetan Plateau adjacent to and north of the Sichuan Basin poses a fundamental geodynamic problem; the topography of eastern Tibet apparently developed in the absence of significant shortening of the upper crust. This study investigates the development and subsequent evolution of the topographic margin of the plateau in an effort to ascertain the controls on and geodynamic significance of present day topography. The primary results from this study are threefold, and include: 1) an estimate of the inception of high relief along the plateau margin in the Late Miocene; 2) documentation of active deformation in the Min Shan range and estimates of the rates and pattern of Pleistocene-Recent rock uplift; 3) an assessment of the controls on the spatial distribution of bedrock channel gradients in this landscape. Thermal histories of rocks along the margin inferred from *Ar/39Ar and (U-Th)/He thermochronology provide constraints on the long-term rates and distribution of denudation across this margin of the plateau. Results indicate that 1) prior to the Late Miocene (ca. 11 Ma) regional denudation rates were low (< 0.1 mm/yr), and 2) rocks adjacent to the plateau margin were exhumed from depths of 8-10 km since that time. Active deformation and rock uplift in the Min Shan is documented by tilted Pleistocene basins along the western range flank. Geologic mapping and chronology demonstrate that rates of tilting are rapid (~108 rad/yr), and that rock uplift is highest near the range crest. However, mapped faults adjacent to the range do not appear to exert a direct control on the distribution of rock uplift. Analysis of bedrock river longitudinal profiles reveals a region of steep channels (normalized for drainage area) adjacent to the topographic front of the plateau margin. The spatial distribution of channel steepness appears to reflect active rock uplift focused along the plateau margin. Thus, the high topography along the plateau margin is argued to be a dynamic response to rock uplift in the absence of significant horizontal shortening and may reflect thickening in the lower crust. / by Eric Kirby. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1997. / Includes bibliographical references (p. 203-213). / by Jie Zhang. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2004. / Includes bibliographical references. / We develop a framework for interpreting geodetic measurements of interseismic deformation and geologic slip rate estimates in terms of block motions. This method accounts for the effects of block rotations and interseismic strain accumulation from active fults. We find that the San Andreas Fault slips close to Its Holocene rate in the Carrizo Plain (35.6 [plus-minus] 0.5 mm/yr) but is five times slower near San Bernadino (6.6 [plus-minus] 2.7 mm/yr). Thrust faults underneath Los Angeles, the Ventura Basin, and the San Gabriel range front all exhibit active shortening from 0.5 to 13.5 mm/yr. We suggest that differences between paleoseismic and block model slip rate estimates may be explained by changes in fault slip rates through the Holocene. The viscoelastic rheology of the non-brittle upper lithosphere may give rise to time dependent surface deformation though the seismic cycle. We extend a classic theory from periodic to temporally clustered earthquakes by superposing several out of phase earthquake cycles. This new model displays a much wider range of behaviors than does the periodic earthquake cycle model and provides a mechanism to explain apparent discrepancies between geologic and geodetic slip rate estimates. The potential for large earthquakes in an active fault system is determined by the balance between coseismic moment release and interseismic moment accumulation. We identify regions of local moment deficit in Southern California by comparing historical earthquake catalogs with the fault slip rate catalogs derived from both geologic and geodetic data. Large moment release deficits are localized in the northern Mojave Desert, San Jacinto fault, San Andreas fault, and the greater Los Angeles area. We estimate the / (cont.) minimum size earthquake sources (M > 7) required to relieve these deficits. / by Brendan J. Meade. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1995. / Includes bibliographical references (leaf 28). / by Andrew Clifton Humphrey, Jr. / M.S.

Thesis (Ph. D. in Climate Physics and Chemistry)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 161-167). / Methane (CH 4 ), nitrous oxide (N20) and sulfur hexafluoride (SF6) are powerful greenhouse gases with global budgets that are well-known but regional distributions that are not adequately constrained for the purposes of mitigation and policy initiatives. Quantifying emissions using inverse approaches at the national scale requires measurements that specifically target the region of interest. Primarily due to the lack of atmospheric measurements from the region, emissions estimates of these greenhouse gases from India have largely been missing. New in situ measurements of atmospheric mole fractions from a Himalayan station in Darjeeling, India (27.03'N, 88.26'E, 2200 meters above sea level) have been collected from December 2011 for CH4 and March 2012 for N20 and SF6 to February 2013 using high-precision instrumentation that is linked to the Advanced Global Atmospheric Gases Experiment (AGAGE). These measurements comprise the first high-frequency dataset of these gases collected in India and are used for measurement-based assessment of emissions. Several features are identified. In SF6 , the signal associated with Northern Hemispheric background is typically present. CH4 and N20 mole fractions are almost always enhanced over the background, suggesting strong regional sources. Additionally, a diurnal signal resulting from thermally driven winds is seasonally present. A particle dispersion model is used to track 'air histories' of measurements, quantifying the sensitivity of concentrations at Darjeeling to surface emissions. The effect of topography on the derived air histories is investigated to test the robustness of the model in simulating transport in this complex environment. The newly acquired data set is used to investigate the ability of the model to reproduce signals that stem from the mesoscale diurnal winds. The sensitivities of meteorological resolution and particle release height are investigated to better quantify some of the uncertainties associated with this chemical transport model. A Quasi-Newton inverse method is used to estimate emissions at monthly resolution. CH4 , N20 and SF6 emissions from India are found to be 44.3% Tg yr- 1, 825 1045/707 GgN yr- 1 and 221 241/205 kton yr-', respectively. Significant uncertainty reduction is seen on emissions from India during the summer when the monsoon results in high sensitivity over the subcontinent. / by Anita Lakshmi Ganesan. / Ph.D.in Climate Physics and Chemistry

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2004. / Includes bibliographical references (p. 172-180). / Methane (CH₄) and carbon dioxide (CO₂) are the two most radiatively important greenhouse gases attributable to human activity. Large uncertainties in their source and sink magnitudes currently exist. We estimate global methane surface emissions between 1996 and 2001, using a top-down approach that combines observed and simulated atmospheric CH₄ concentrations. As a secondary study, we describe our participation in a CO₂ inverse-modeling intercomparison. The available methane time-series data used in this work include observations from 13 high-frequency stations (in-situ) and 74 low-frequency sites (flask). We also construct an annually-repeating reference emissions field from pre-existing datasets of individual methane processes. For our forward simulations, we use the 3-D global chemical transport model MATCH driven by NCEP meteorology. A prescribed, annually-repeating OH field scaled to fit methyl chloroform observations is used as the methane sink. A total methane source of approximately 600 Tg yr⁻¹ best reproduces the methane growth rate between 1993-2001. Using the reference emissions, MATCH can reproduce the observed methane variations at many sites. Interannual variations in transport, including those associated with ENSO and the NAO, are found to be important at certain locations. We adapt the Kalman Filter to estimate methane flux magnitudes and uncertainties between 1996 and 2001. Seven seasonal processes (3 wetland, rice, and 3 biomass burning) are optimized at each month, while three aseasonal processes (animals/waste, coal, and gas) are optimized as constant emissions. These optimized emissions represent adjustments to the reference emissions. For the entire period, the inversion reduces coal and gas emissions, and / (cont.) increases rice and biomass burning emissions. The optimized seasonal emission has a strong peak in July, largely due to increased emissions from rice producing regions. The inversion also attributes the large 1998 increase in atmospheric CH₄ to global wetland emissions, consistent with a bottom-up study based on a wetland process model. The current observational network can significantly constrain northern emitting regions, but is less effective at constraining tropical emitting regions due to limited observations. We further assessed the inversion sensitivity to different observing sites and model sampling strategies. Better estimates of global OH fluctuations are also necessary to fully describe the interannual behavior of methane observations. Carbon dioxide inversions were conducted as part of the Transcom 3 (Level 1) modeling intercomparison. We further explored the sensitivity of our CO₂ inversion results to different parameters. / by Yu-Han Chen. / Ph.D.