b'Education matters 5 s in directions oblique to the EarthsThe magnetotelluric (MT) method is ofmodel and hybrid impedance. To rotation axis than directions parallelparticular interest when investigatingdo so, structurally simple forward to the equatorial plane (anisotropythe upper mantle as it is primarilymodels of both standard and hybrid of 0.8%). Our inner-core shear-wavesensitive to electrical conductivity. Fromimpedances are calculated. The anisotropy observations place newelectrical conductivity, conclusionsconductivity structure of this model constraints on the inner core mineralregarding the temperature, pressure,was constrained by a 3-dimensional composition. Finally, we extend thephysical and chemical state, porosity,inversion of continental MT data, principles to cross-correlations betweenand permeability of rocks can becontrolled source EM (CSEM) data, and source events and devise a new way toinferred. my reference model. From this model, build global inter-source correlations.This thesis examines laboratoryhybrid impedances are observed We demonstrate that a single seismicconductivity measurements withto reproduces four decades of data station is sufficient to construct a globalocean-bottom MT data collected frommeasured by numerous receivers. correlogram. The correlogram exhibitsthe Pacific Ocean. From these data,From this evidence, I conclude that my prominent features sensitive to theI create an upper mantle referencereference model constrains the LARC internal planetary structures. We showmodel for electrical conductivityand that it realistically represents the implementations to constrain the theand propose a hybrid MT impedanceupper mantle. Additionally, I conclude Earth and Martian core size and confirmwhich improves the bandwidth andthat my hybrid impedance is a useful a large Martian core. This provides aconfidence intervals of ocean-bottomalternative to traditional MT impedance new paradigm for imaging planetaryMT data. Between 50 km and 100when conducting ocean bottom MT interiors on a global scale with currentlykm depth, MT data predicts variablestudies.realizable resources in planetaryelectrical conductivity structures. My missions. reference model is able to encapsulateKhumo Leseane, Monash University: Sheng has been awarded the 2022this variability with a function whichTectonic evolution of Macquarie Arc using American Geophysical Unions Study of thevaries according to hydration, partialconstraints from geophysicsEarths Deep Interior Award for Graduatemelt, and the age of the overlying Research (AGU-SEDI Award) for theoceanic lithospheric. For 200 km to research conducted for his PhD. 400 km, the hydrated end-member of this reference model predicts Jake MacFarlane, University ofthe convergence of conductivity Adelaide: Understanding marinestructures with increasing depth magnetotellurics observable in published conductivity structures. As such, this reference model constrains the presence of hydration and partial melt within the LARC for a range of lithospheric ages and is a representative model of the Earths oceanic lithosphere and asthenosphere. Following an analysis of ocean-bottom EM field observations, I observe the attenuation of magnetic field variations by the conductive ocean water. This attenuation results in MT impedances that are difficult to interpret using available modelling algorithms. In contrast, the calculation of a hybrid MT impedance using The theory of plate tectonics proposesocean-bottom electric and continental that the Earths lithosphere is separatedmagnetic fields is observed to improveThis interdisciplinary study uses joint into rigid plates, which are capable ofthe signal-to-noise ratio. This improvedgravity and magnetic interpretation motion through interactions with thesignal-to-noise ratio extends theand modeling, geology, and a underlying asthenosphere. Followingusable bandwidth of ocean-bottomsynthesis of geochronology and its adoption in the 1960s, it hasMT data from just over one decadegeochemistry data to understand become the prominent theory usedto approximately four decades. It isthe Ordovician to Permian tectonic to understand geodynamic processesimportant to note that this impedanceevolution of the southeastern Lachlan within the Earth. The mechanisms ofrepresents the normalisation ofOrogen. There is a focus on the role of tectonism are of particular interestocean-bottom electric fields usingpre-existing (or inherited) structures due to their implications regardingcontinental magnetic fields. As aduring major tectonic events. the formation of economic resources.consequence, alterations must beThe Lachlan transverse zone is an Despite numerous studies attemptingmade to modelling algorithms beforeinherited structure that formed along to characterise these mechanisms, theattempting to reproduce hybridthe northern margin of a stranded lithosphere-asthenosphere rheologicalimpedances. microcontinent. This structure contrast (LARC) remains an enigmaticFinally, a case study is conducted tohas influenced the distribution of component of plate tectonic theory.assess the validity of my referencemagmatism, and has controlled DECEMBER 2022 PREVIEW 30'