An Overview
Major: Applied Mathematics
Academic Affiliation: Georgia State University
Biography
Teodora’s passion for nature and interest in applied mathematics was combined when she discovered geophysics. Born in Romania, raised in Georgia, she seeks to travel the world to observe and study numerous Earthly processes with a numerical perspective.
Abstract
2018- Imaging the Subsurface: The Effect of Logjams on Groundwater-Surface Water Exchange
Conventional methods of quantifying subsurface interactions in streams are often insufficient in characterizing hydrological processes and demand better techniques to measure complex dynamics. Point-measurements are incomplete and do not provide direct data on hyporheic exchange, a mixing of surface and subsurface water under and around a stream capable of influencing ecosystem processes. Fortunately, geophysical techniques can improve analysis of the hyporheic zone. For the first time in a field setting, we apply electrical resistivity imaging (ERI) to a mountainous stream below a channel-spanning logjam to estimate the extent of hyporheic exchange. Previous studies suggest logjams increase hydraulic resistance and drive water deeper into the hyporheic zone; our results imply water remains in the subsurface longer around a logjam, thus increasing a stream’s ability to process nutrients and solutes. A comparison between fluid conductivity and bulk conductivity proved ERI as a more spatially comprehensive technique in quantifying the extent of hyporheic exchange. These results highlight the critical role that logjams play in hyporheic zone dynamics, which could affect ecosystem health: future applications of this study can aid in conserving, managing, and restoring riverine systems.
2019- Deep-crustal Deformation: An Experimental and EBSD-based Study of Amphibole’s Seismic Anisotropy
Seismic anisotropy is a powerful tool for imaging the deep crust and identifying deformation structures at depth. However, interpreting these geophysical signals remains difficult due to a lack of geologic and mechanistic constraints on their formation. Strong lattice preferred orientations (LPOs) of anisotropic minerals create significant seismic anisotropy, and the formation of these LPOs is intimately related to the style and conditions of deformation. We investigate anisotropy and LPO formation in amphibole, a common anisotropic deep crustal mineral, using deformation experiments and EBSD analysis. Two fine-grained, pure amphibole samples were experimentally hot-pressed for 16 hours at deep crustal conditions (1.5GPa, 750 C). Subsequently, one sample was deformed using a Griggs-type apparatus at strain rates of 106-10-3 s-1 while the other was recovered undeformed.
Microstructural observations show that both the undeformed and deformed samples exhibit strong LPOs. The undeformed sample shows minimal intragranular misorientations, suggesting that grains underwent rigid body rotation during-hot pressing, where elongated grained oriented themselves with the long [001] axis along the shear plane which developed a moderate LPO (J-Index: 2.39). However, the deformed sample has an even stronger LPO (J-Index: 2.75), and exhibited significant intragranular misorientations and subgrain formation, indicative of dislocation activity. Hence, it appears that the initial, rigid- body rotation induced LPO is subsequently modified by creep. The resultant calculated P-wave seismic anisotropy (AVp) for the deformed sample is 9.9%, while the undeformed sample’s AVp is 10.4%. In the deformed sample, LPO variation with grain size was also investigated. Large grains (>2µm) exhibit a stronger LPO and 10.6% AVp, while the fine grains have a moderate LPO and 8.1% AVp. This work demonstrates that amphibole is susceptive to rigid- body rotation induced LPO formation due to its crystal habit, with deformation modifying LPO only mildly under the explored conditions. In all, hot pressing and deformation of amphibole at deep crustal conditions lead to strong LPOs and seismic anisotropy, suggesting that deformed amphibole may be a significant contributor to deep crustal seismic anisotropy.
Posters
Imaging the Subsurface: The Effect of Logjams on Groundwater-Surface Water Exchange
Deep-crustal Deformation: An Experimental and EBSD-based Study of Amphibole’s Seismic Anisotropy