b'Education matters Antarctica are sloped forward into theThis thesis presents a compilationpresence of J (shear) waves in the Earths ocean forming an ice cavity underneath.of published works featuringinner core. These shear wave signals are The turbulent transport of heat and saltmethodological and theoretical advancesdirect evidence to confirm the solidity into the ice interface melts the ice andfor exploiting correlation methods forof the Earth deepest shell. To match the drives convective wall plumes that playearthquake coda. The fundamentalcharacter of the observed correlograms a a crucial role in the basal melting. Ice- objectives include (i) improving data2.5% reduction of inner core shear wave bathymetry and various ambient flowsprocessing, (ii) understanding of thespeeds relative to spherically symmetric like tides, waves and sub-mesoscalenature and generation mechanism ofmodels of the Earth is inferred. With further eddies further modify the plumes. Thebody-wave-like correlation features,refinements, the correlation wavefield regional and global ocean models work(iii) applying new understanding toapproach could lead to improved at scales over 100 meters and rely onstudy Earth structures. In particular, thestructural constraints on the Earth interior, crude sub-grid scale parameterizationthesis contributes to local, regional andespecially for poorly sampled regions such of convection and turbulent processesglobal scale problems. At the local andas the lowermost mantle and core.at the ice-ocean boundary layer, causingregional scales, contributions are made uncertainties in the estimation ofto the development of the teleseismic PChris Li, University of Adelaide: the melt rate. Over the course of mywave coda autocorrelation method forImproving next-generation dissertation I have examined the role ofimaging near-surface structures. At thehydrogeological models with geophysicsmicro scale turbulent processes at the iceglobal scale, a new concept the global ocean boundary using Direct Numericalcorrelation wavefield, which is relevant to Simulation (fully resolving convectionstudies of the deep Earth, is introduced.and turbulence). We carry out simulationsSeismic waves from distant earthquakes by varying the slope of the ice shelves,illuminate stratified structures beneath changing the strength of ambient flowa receiver in a nearly vertical fashion. and including sub glacial discharge.Stacked autocorrelations of the portion Our results show that the melt rate isof ground motion records immediately controlled by the slope of the ice-faceafter the P wave arrivals (i.e., the P with decreasing melt rate at shallowerwave coda) are constructed to extract slopes. Over the geophysical flow regime,reflection signals from shallow subsurface convection is still a key parameter thatdiscontinuities beneath individual controls the heat and salt transfer intostations. The processing incorporates a the ice-face and hence the melt rate. Thespectral whitening operation to enhance results from this study significantly widenthe quality of autocorrelation results. The our present understanding of the basalfeasibility of the method is demonstrated melting and can improve the ice-oceanthrough synthetic and field data. The parameterizations for large-scale models. improved procedure is then applied to a Thanh-Son Pham, Australian Nationallarge number of seismic receivers across University: Advancing correlationAntarctica to obtain estimates of the methods of earthquake coda in seismicthickness and the ratio of P to S wave body wave studies speed for the ice cover. These estimates are in a good agreement with priorThis thesis presents advancements The discovery of long-range spatialmeasurements mainly obtained fromto the disciplines of geophysics and correlation in earthquake coda andactive seismic and radar methods. Thishydrogeological modelling. There are ambient noise records has had far-reachingsuccessful application for the Antarctic icethree main scientific contributions in this impacts on modern seismology. Thiscover proves the potential of the methodwork. Firstly, a method is presented to approach provides a conceptual frameworkfor studying other shallow structurescouple time-domain electromagnetics to extract information about the structureincluding sediment, regolith or ice covers(TEM) and surface nuclear magnetic of the Earth from stacked cross-correlationsin other continents and on other planetsresonance (NMR) datasets with limited as a function of inter-receiver distance (i.e.,in future space missions. drillhole data to provide information on correlograms) using noisy seismic records.Using the insights gained from thehydrogeological properties in a non-Early work concentrated on the retrievalautocorrelation case study, the crossinvasive manner, including groundwater of surface waves travelling betweencorrelation of the late coda of largesalinity and hydraulic conductivity. receiver pairs from ambient noise andearthquakes recorded at seismic receiversThis method reduces the ambiguity in used measurements of their dispersion inaround the globe is exploited. The globalthe hydrogeological interpretations of surface wave tomography applications.correlograms reveal a wealth of correlationTEM data by coupling with the porosity Later it was found that body-wave-likefeatures, including correlation phases thatvalues independently estimated using signals also emerge in correlograms.have timing properties similar to regularsurface NMR. The method was applied Intriguingly, many feeble signals that areseismic phases from a surface source,to a South Australian River Murray sensitive to deep Earth structures can alsoand others that do not have counterpartsfloodplain to investigate the impact be extracted efficiently from late codain the direct wavefield. All features inof artificial watering on the shallow of large earthquakes. Yet, the nature ofthe correlation wavefield are producedgroundwater salinity. The second correlation features in coda correlogramsfrom the similarity of the waveforms ofscientific contribution is evaluating has remained a puzzle. Disentangling thattwo regular seismic phases sharing athe impact of incorporating TEM and puzzle is a key to open new avenues forsubset of propagation legs. These novelsurface NMR datasets on the prediction deep Earth studies. insights are then used to identify theerror and uncertainty of groundwater 31 PREVIEW DECEMBER 2020'