School of Earth Sciences - Theses
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ItemThe Variation of atmospheric carbon dioxide,methane and nitrous oxide during the holocene from ice core analysis(University of Melbourne, 2004)Recent studies have demonstrated that the atmospheric concentrations of radiatively important greenhouse gases, including methane (CH4), carbon dioxide (CO2), nitrous oxide (N2O) and carbon monoxide (CO), have significantly increased during the past 200 years due to anthropogenic emissions. Analysis of air trapped in polar ice cores allows for past atmospheric variations due to natural climate conditions to be investigated, placing recent changes in a historical context. In this thesis new high- precision, multispecies measurements of atmospheric trace gas concentrations during the Holocene have been produced by analysing the air trapped in the ice at Law Dome, East Antarctica (66�46'08"E, 112�48�28�S). The ice core records are well-dated, have high age resolution and overlap with modem instrumental records due to the high accumulation rate at the drilling sites. The combination of high age resolution, precise dating and high precision measurements allows for subtle, decadal-scale variability to be detected. The multispecies measurement technique allows for biogeochemical causes of variations to be identified. The first part of this study focused on the late Holocene period (AD 0 to 1975). New high-precision records of CH4, CO2, N2O and CO have been produced for this period. The CH4 and CO2 measurements are used to build upon the existing Law Dome records of these gases during the last 1000 years, to validate and further define previously observed variations. The new measurements extend the records of these gases by another 1000 years. As a consequence of the multispecies measurement technique it has been possible to also measure N2O and CO during this period. These new measurements highlight the atmospheric response to the Little Ice Age (LIA) cooling (AD 1550 to 1800), particularly a 10 ppm decrease in atmospheric C02 between AD 1550 and 1600. A stabilization of CO2 during the 1940s was also confirmed in the Law Dome record. Increased data density during this period shows that the atmospheric CO2 mixing ratio stabilized at ~310 ppm between 1937 and 1955. New signals were observed in the extended records, including a 100 ppb increase in the CH4 concentration between AD 0 and 1800, which is probably the result of increasing pre-industrial anthropogenic emissions. The second part of this study focussed on the CO2 and CH4 response to a rapid, abrupt cooling at 8,200 years BP. The Law Dome (DSS) measurements are complemented by four measurements of NorthGRIP (Greenland) ice core. A decrease of at least 52 ppb CH4 is observed in the DSS record, and a decrease of at least 62 ppb is observed at NorthGRIP during the same period. A smaller CO2 response of 4 to 5 ppm is seen in both the records. The CH4 signal is used to improve the chronologies of these ice cores by synchronising with other well-dated CH4 records, specifically GRIP (Greenland) and Dome C (Antarctica).
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ItemThe geology, petrology and geochemistry of the granitic rocks of Victoria(University of Melbourne, 1973)In the field the granitic rocks of Victoria show a wide variety of characteristics but chemically all are related and are the result of similar processes that occurred cyclically during the Palaeozoic. The granites may be divided into two groups on the basis of whether or not primary hornblende is present in the more basic members of the suite. Rocks of the hornblende-free series concentrate mainly in central Victoria and usually contain biotite that is red-brown in colour. In the granites of the hornblende-bearing group green-brown biotite is generally present. The two different colours appear to indicate unlike oxygen fugacities in the magmas from which the micas crystallized. The rocks of the hornblende-bearing and hornblende-free provinces also vary slightly in chemistry - the most important difference being that the basic members of the first group contain slightly more Ca than those of the second having comparable silica content. The compositions of the Victorian granites is consistent with their derivation by anatexis of a mixture of basic igneous rocks and sedimentary material. The conclusion is drawn that a combination of Cambrian basalts and dolerites and Cambro-Ordovician sediments constitute the source. The explanation of the fact that two chemical trends are observed in the granites may lie in the possible existence of two chemically distinct groups in the Cambrian igneous rocks - the one having lower Ca predominating under central Victoria.
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ItemPetrogenesis of the Melba Flats Ni-Cu-PGE Deposit in Western Tasmania: Insights from a Geochemical and Geochronological Investigation( 2016)Since its discovery in 1893, the Melba Flats Ni-Cu-PGE deposit has produced 10,000 tons of Ni and Cu at an average grade of 9.7% and 4.7% respectively. It is a magmatic sulphide deposit located 8 km north-east of the township of Zeehan, along the eastern margin of the Dundas Trough in Western Tasmania. The deposit is associated with a suite of bifurcating mafic intrusions hosting magmatic Ni-Cu-PGE sulphides intruded into a sequence of volcaniclastic lithic greywackes, which are correlated to the Crimson Creek Formation. U-Pb detrital zircon geochronology was utilized to show that the Melba Flats sediments have a maximum depositional age of c. 582 Ma. The Melba Flats mafic intrusions were formed by primitive magmas with 13 to 16 wt% MgO and a sub-alkaline tholeiitic affinity. 40*Ar/39Ar hornblende geochronology was employed to establish that the mafic intrusions were emplaced at c. 568 Ma, along an attenuated continental margin characterized by a transitional rift setting, analogous to the early Paleogene break-up margin of East Greenland. Melba Flats Ni-Cu-PGE sulphides are characterized by massive-to-semi-massive sulphides that possess high Ni, Cu and PGE tenors and mantle-like δ34S values and S/Se ratios and disseminated sulphides that have low Ni, Cu and PGE tenors, along with crustal δ34S values and S/Se ratios. Geochemical data indicates that the massive-to-semi-massive sulphides were formed at depth before being transported to their current sites, whilst the disseminated sulphides were formed during transport as the primitive magma interacted with the S-bearing crustal rocks.
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ItemEvaluation of aerosol representation by ACCESS-CM2 with increased aerosol-chemistry complexity in the Southern Ocean( 2020)This thesis identifies the inherent biases of aerosol parameters within the next-generation Global Climate Model (GCM); the Australian Community Climate and Earth System Simulator Coupled Model (ACCESS-CM2). GCMs poorly represent clouds and aerosols over the Southern Ocean, resulting in systematic shortwave (SW) radiation biases with widespread global energy budget impacts. This research determines whether a more complex, physically-representative aerosol-chemistry scheme may reduce the Southern Ocean radiation bias, and the inherent aerosol biases established within ACCESS-CM2. Southern Ocean aerosols are dominated by sea-salt and biogenic products. This study ran a control ACCESS-CM2 simulation and three perturbation simulations, which altered either the representation of Primary Marine Organic aerosols, sea-salt, or implemented a fully interactive chemistry scheme respectively. A suite of ground-based and satellite observations was collected and compared against each simulation to establish model bias respective to key aerosol metrics including Aerosol Optical Depth (AOD), Cloud Con- densation Nuclei (CCN) and SW radiation. Simulation biases were explained through model-observation comparisons of aerosol chemistry, size and number parameters. Overall, ACCESS-CM2 exhibited a substantial positive bias in Aerosol Optical Depth (AOD) and SW radiation, and underestimated Cloud Condensation Nuclei concentration. This research suggests that increasing the complexity of aerosol schemes was able to provide a closer model agreement with observed aerosol metrics of AOD and CCN. Fully interactive chemistry provided the best reduction in both AOD and CCN bias. However, modified aerosol schemes have negligible effects upon the inherent SW radiation bias in ACCESS-CM2, suggesting further research into cloud schemes is necessary.
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ItemNo Preview AvailableAntarctic sea ice and its interactions with high latitude weather and climate( 1998)Antarctic sea ice plays a major role in the earth system by greatly influencing the high latitude exchanges of heat, moisture and momentum between the ocean and atmosphere, as well as profoundly effecting the salt budget of the ocean, and thus the production of Antarctic Bottom Water, one of the driving mechanisms of worldwide oceanic circulation. With such considerable and far reaching impact, it is important to document its climatology, understand its variability and quantify its influence. Climatologies and trends of the Southern Ocean sea ice pack are presented using the most recent satellite observations available from the Defense Meteorological Program’s (DMSP) Special Sensor Microwave Imager (SSM/I). The analysis of these data show that Antarctic sea ice is highly variable in both time and space. Statistically significant increases in the sea ice extent, open water and ice areas have been determined from the SSM/I data for the 9 year period 1987 to 1996, a result which differs from the Scanning Multichannel Microwave Radiometer (SMMR) observations (1978-1987). The increasing trend in the SSM/I observations can be attributed to the large increases in sea ice observed in 1994-1995, as confirmed by an analysis of data from the ERS-1 satellite. The mean season length during these years has remained relatively unchanged. Regional trends, both in the sea ice concentration and in season length, showed vast spatial inhomogeneity. SSM/I data displayed increasing season length in the central Weddell Sea, Bellingshausen Sea and Balleny Islands regions, with decreasing length in the Amundsen Sea, eastern Ross Sea and in the coastal areas off Wilkes Land. Similar trends are observed in the seasonal sea ice concentration. In most cases, these trends are opposite to those observed in the SMMR data, which may be linked to the shift observed in the Amundsen Sea low after 1990. Comparisons with historical data would suggest that no large scale anomalous change has occurred in the Antarctic sea ice limits over the course of human observation. Furthermore, the degree of variability suggests great care is needed in interpreting large scale changes in sea ice conditions, and hence atmospheric or oceanic change, from locally observed anomalies. Case studies of the effect of individual cyclones upon the sea ice concentration show small but definite modification of the ice conditions. To further diagnose aspects of the thermodynamic and dynamic forcing upon the Antarctic pack, detailed analysis of the sea ice concentration variability has been conducted using spectral techniques, and the spectra have been compared to those of the European Centre for Medium Range Weather Forecasts (ECMWF) temperature and wind data. In all cases, and with the seasonal cycle removed, the sea ice concentration shows a bias towards longer timescales of variability than either the wind stress or surface air temperature. This “red shift” in its frequency spectrum is strongest with the wind stress, and weakest with the temperature. For longer period waves, this may be due to the formation of new ice by surface cooling or the moderation of melting by the cold surface water, whereas for shorter period waves, where wind stress dominates temperature and ice concentration respectively, time is required for winds to draw in warmer or cooler air, as well as to overcome the ice masses inertia and keel friction to open or close leads. Strong intraseasonal variability of the sea ice concentration is observed in the 20-25 day period, reflecting similar timescales of the temperature variability, as well as that of the energetic eddies of the Antarctic circumpolar current. Examination of the latitudinal variation of the sea ice concentration, temperature and wind stress spectra showed not only the importance of the north-south temperature gradient in influencing the variability, but also the seasonal changes in the semi annual oscillation of the circumpolar trough. Regional spectra showed clear differences between location, and reflected the influences of the atmosphere and ocean upon the sea ice pack. This is clearly shown in the Weddell Polynya region and off East Antarctica, with high variability in the synoptic timescales, and in the western Ross Sea where changes occur in timescales of greater than 20 days. In order to determine if satellite derived, real time sea ice concentration and distribution would be of benefit to operational numerical weather prediction (NWP) schemes, the effect of sea ice concentration change upon the atmosphere in synoptic timescales was examined using a general circulation model in conjunction with the Australian Bureau of Meteorology’s GASP analyses. Experiments were conducted with a typical July sea ice concentration and distribution, as well as slab concentrations of 0, 10, 25, 50, 80 and 100%. Results from 5-day numerical weather forecasts show that the central pressure, structure and tracks of individual cyclones are sensitive to the ‘switch on’ of different sea ice conditions. Composites of all forecasts made with each concentration showed considerable, and mostly statistically significant, anomalies in the surface temperatures and turbulent heat fluxes over the sea ice. The magnitudes of these changes varied monotonically with the area of open water. The largest changes were simulated closest to the coast for all concentrations except for the typical July sea ice run, which displayed maxima over the outer pack. Significant westerly anomalies were induced over the ice in all cases, as were reductions in mean sea level pressure. The July sea ice runs displayed a distribution of the mean sea level pressure anomaly different from all others, with maxima occurring in the central to outer pack. All other forecasts displayed maxima at the coast. The results suggest that sea ice concentration does induce anomalies in the atmospheric parameters in timescales of less than five days. Further, the use of a realistic distribution of sea ice concentration produces results distinct from the constant concentration forecasts. Hence it is suggested that real time Antarctic sea ice data may be of considerable benefit to numerical weather prediction models.
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ItemThe influence of a sub-lithospheric decoupling layer on subduction zone surface motion, mantle circulation and slab dynamics( 2020)The lithosphere consists of a strong surface layer fragmented in a series of major and minor tectonic plates moving over a weaker and more buoyant layer of asthenospheric material. The boundary between the lithosphere and asthenosphere, the LAB, is a critical element of plate tectonics as it mechanically decouples the motion of strong tectonic plates from the ow in the underlying weaker mantle. Recent geophysical observations report an abrupt seismic velocity decrease and electrical conductivity increase beneath certain segments of the subducting Pacific plate, which may represent the channelised base of the subducting oceanic lithosphere. This inferred sub-lithospheric weakness is predicted to lubricate the base of subducting plates and enforce the decoupling at the LAB, with potential implications for our understanding of subduction geodynamics. However, little is known about the impact of this feature on subduction zone dynamics. This research work for the first-time compiles worldwide observations of a very thin and weak sub-lithospheric layer (SLL) embedded beneath the base of a descending oceanic lithosphere and computationally simulates SLL effects on subducting plate and mantle dynamics. In the last few decades, the rapid progress in technology has contributed to increasing complexity of geological observations and capacity of computational infrastructures. With direct geological observations limited in both time and space scales, computational modelling offers the extraordinary opportunity to test different hypotheses for Earth's evolution through geologic time and ongoing processes, whilst promoting the development of multidisciplinary approaches. This study, therefore, employs subduction numerical models and addresses the SLL impact on slab deformation style including subduction surface motions, induced mantle ow and patterns of seismic anisotropy. Our results show that the physical properties of the sub-lithospheric layer fundamentally control the partitioning of surface motions between trench migration and horizontal plate velocities, but also the partitioning of the induced mantle ow as it splits into its poloidal and toroidal components. A regional SLL mechanism firstly provides a novel explanation for the high convergence and low trench migrations rates observed globally at natural subduction zones. Then, an SLL also delivers an alternative answer for plate margins characterised by some degree of toroidal ow and for the apparent lack of a direct link between buoyantly driven convection (which drives only vertical and divergent motion) and the generation of toroidal energy (which corresponds to strike slip motion and plate spin). Additionally, a very thin and weak sub-lithospheric layer promotes the alignment of the maximum strain axes in the direction parallel to plate motion within the oceanic lithosphere and mantle directly beneath it, and in the direction parallel to the trench deeper in the sub-slab mantle. As a result, these findings contribute to the resolution of the slab anisotropy debate on whether an SLL can substantially influence three-dimensional ow around the subduction zone. These outcomes reveal that a very weak and thin sub-layer embedded in the Earth's uppermost asthenosphere impacts the complexity of current natural subduction systems, for which little predictive and holistic modelling exists. By acting as a slippery base for the motion of the subducting lithosphere, this layer sharpens the decoupling between the strong tectonic plates and the weaker mantle underneath. This has significant consequences on slab subduction style and patterns of seismic anisotropy as observed in several subduction regions, such as Izu-Bonin-Mariana, Central America and Kamchatka- Aleutian among others, where the presence of this layer is confirmed by geophysical studies. This thesis work ultimately aims to provide a novel conceptual framework to reinterpret the geological record of complex plate-margins, with broader implications for better understanding the evolution of the Earth's dynamic system.
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ItemStress interactions in intraplate earthquakes( 2020)Australia is a seismically active continent with an intraplate compressive stress field primarily driven by far-field plate boundary interactions. Major (magnitude >= 5) surface-rupturing earthquakes are primarily sourced from reverse faults. Major earthquakes perturb local-to-regional stress fields and influence the spatiotemporal properties of subsequent earthquakes. This thesis first contextualizes Australian earthquakes against global comparatives by investigating 260 finite-fault rupture models for 137 moment magnitude (Mw) 4.1 to 8.1 continental earthquakes worldwide. I find that: (i) Australian earthquakes are amongst the most kinematically and geometrically complex for their Mw, (ii) upper-bounds and variance of the number of faults that rupture co-seismically increase with increasing Mw, and (iii) multi-fault rupture populations show no dependency on strain rate or proximity to plate boundaries. The thesis then presents a suite of studies that model static and viscoelastic coulomb stress changes (dCFS) imparted by major Australian earthquakes on to receiver faults and in the surrounding crust. I find that static dCFS models provide an informative physical-statistical basis for characterising many seismic sequences in Australia, with some exceptions. Aftershocks occur predominantly within positive static stress lobes and close to the advancing viscoelastic positive stress lobes, especially over the first few decades after major earthquakes in these regions. Earthquake triggering appears to occur under stress perturbations as small as approx 0.001 to 0.01 bar, suggesting cratons contain regions of critically stressed lithosphere. The effects of varying source fault geometries and kinematics on dCFS fields and subsequent seismicity are used to show how progressive refinement of source fault models using emergent data can reduce epistemic uncertainties in the role of dCFS in earthquake triggering. In some instances, increased source model complexity does not significantly impact on dCFS results and possible relationships to aftershocks relative to simple source models. The thesis finally investigates the role of lithospheric-scale flexural bending due to eustatic sea level changes, and whether these impart dCFS perturbations on finite faults and in regions similarly to stresses imparted by preceding earthquakes. Preliminary age distributions of large paleo-earthquakes on these reverse faults are concurrent with dCFS peaks imparted by eustatic sea-level changes. dCFS of > 0.1 to > 1 bar on faults during the low-stand Marine Isotope (MIS) Stage 2 to Stage 4 interval (ca. approx 30 to approx. 70 ka) provides tentative evidence that earthquake clusters could be stimulated by sea-level lowstands. This thesis demonstrates the power and utility of dCFS modelling to improve understanding of intraplate earthquakes.
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ItemModelling Australia’s transition to a low carbon electricity system with optimised transmission networks and renewable energy exports( 2020)In order to meet the Paris Agreement and pursue efforts for a 1.5 degrees Celsius target, the electric power system worldwide must undergo a fundamental transformation as the main pillar for decarbonisation. The decarbonisation will almost certainly be driven largely by the massive adoption of variable renewables. The objective of this PhD project is to develop a co-optimisation model with the ability to perform comprehensive analysis to simultaneously explore the least-cost configurations of generation, storage and transmission over large geographic regions to facilitate the transition to a low carbon power system. Although applicable to any region, the capacity expansion model we developed focuses on Australia’s National Electricity Market. The capacity expansion calculated by the model satisfies prescribed demand projections and emission abatement targets from 2020 to 2050, subject to constraints including resource adequacy, system inertia and reliability, unit commitment, economic dispatch and transmission capacity. The model also takes into account the decommissioning of the existing fossil fuel generation fleets and explores a great range of renewable generation and storage options. The transmission model employs a Direct Current power flow approximation with 21 major load centres over the eastern states of Australia. We have used the model to examine various carbon abatement scenarios for Australia. We show that wind turbines and solar PV technologies combined with pumped hydro energy storage dominate the solutions, and that gas is unlikely to be a transition fuel towards a 100% renewable system by 2050. The 100% renewables systems simulated are not only technically feasible but also economically achievable. Australia’s vast wind and solar resources become increasingly valuable assets as the world decarbonises. Not only does this study consider meeting local requirements for electricity demand, but also the potential for export of green energy. Our research confirms the very real and great potential for Australia to produce cost-competitive hydrogen. In the pathways to carbon neutrality, we demonstrate there are substantial synergies between renewable hydrogen export and domestic energy transition in Australia. In particular, we show if the hydrogen industry co-locates within the National Electricity Market with shared renewable generation facilities (i.e. sector coupling), not only can the hydrogen industry produce cost-competitive hydrogen, but also that domestic electricity consumers could enjoy lower electricity costs, thereby benefiting the whole economy in the long run. Besides hydrogen export, we also conducted the first detailed least-cost optimisation studies of power system decarbonisation planning for both Australia and Indonesia that considers HVDC interconnections. We show direct electricity export to Indonesia could also benefit Australia’s domestic energy transition as any wind and solar energy not used by Indonesia could then be fed to the National Electricity Market. This could help both countries to achieve decarbonisation. Overall, our modelling suggests that a long-term system-wide perspective and orientation are critical for the design of energy policies that can secure broad energy system benefits. If planned well, Australia could become a major supplier of green hydrogen, direct renewable electricity and energy-intensive products as energy vectors in the global market. Particularly, this could be driven and strengthened by a robust commitment to “net-zero by 2050”.
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ItemFurther development and application of the speleothem U-Pb geochronometer( 2020)Speleothems are valuable archives recording information on past climates and processes of landscape evolution. In fact, the high preservation potential of speleothems and their ubiquity across the globe are key attributes and speleothems are now extensively used in palaeoclimate modelling as complements to the more traditional marine and ice core climate records. The real ’engine’ of speleothems science, however, lies in the ability to reliably and robustly place these archives into chronological context. Historically this has been facilitated by the highly successful U-Th geochronometer, which can accurately date speleothems that formed within the last 650 thousand years. However, many speleothems – and by extension their proxy archives – are far older than this 650 ka limit and so require a significantly longer-lived radiometric methodology: the U-Pb geochronometer has recently filled this void. The U-Pb geochronometer is well known in the geological sciences, but its application to the analytically-challenging medium of speleothems has been relatively recent. Modern mass spectrometry methods now allow the accurate and precise analysis of the extremely low-levels of U and Pb within speleothems, thus providing access to such ’deep-time’ (i.e. multi-million years and further) palaeoclimatic and landscape evolution archives. Despite these significant advances, there remain fundamental impediments to the whole-scale production of speleothem U-Pb ages. This thesis investigates some of these shortfalls with the ultimate aim of advancing the speleothem U-Pb methodology and application such that future speleothem-based studies may more rapidly and more reliably place their reconstruction models into a more robust chronology. The first half of this thesis addresses two fundamental limitations of the speleothem U-Pb method: the large expenditure of time and effort required for producing calcite U-Pb ages, and the potential limitations in the correction for initial isotopic disequilibrium effects in the U-Pb decay chain. To address the former, I provide new software for the rapid production of publication-quality U-Pb isochron figures and ages. Additionally, a new chemical separation (i.e. chromatography) procedure for generating high-purity U and Pb fractions is developed. This new ’stacked resin’ protocol can produce mass spectrometry-ready U and Pb sample aliquots in a single working day – roughly half the time of the previous method – and so accelerates the acquisition of U-Pb ages. In terms of subsequent data deconvolution, the largest hurdle to obtaining accurate speleothem U-Pb ages arguably relates to the uncertainty added from having to estimate an initial isotopic disequilibrium value after the system has returned to equilibrium. As a potential remedy to this problem, this research program develops a framework in which to calculate appropriate disequilibria values for the production of disequilibrium-corrected U-Pb ages. The second part of this thesis is designed to highlight new applications of the calcite U-Pb chronometer made possible by the methodological advances documented in the first half. This research program investigates the utility of speleothems as proxies for regional uplift rates in karst terranes. This is accomplished by producing chronologies for 120 speleothems from the Buchan karst along southeast Australia’s passive margin. The results of this study indicate that SE Australia experienced a renewed period of uplift occurring at a maximum rate of 76 +/- 7 m / Ma beginning at least 3.5 million years ago. This speleothem-derived uplift rate is consistent with other independent regional uplift estimates thus adding credibility to the utility of speleothems as proxies for uplift. The relatively straight-forward method developed here is likely applicable in many future karst studies. Additionally, this research program also investigated the potential applicability of U-Pb geochronology to another form of carbonate archive – stromatolites. The methodological advances described in this thesis were applied to stromatolites from Lake Turkana, Kenya, and the palaeo-lake Bungunnia in southern Australia. The results of this experiment suggest that stromatolites contain too much inherited Pb that simply overwhelms the radiogenic ’age signal’ and so are unlikely to be successful candidates for U-Pb dating, at least for stromatolites formed during much of the Cenozoic period.
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ItemThe structure, rheology, and rupture mechanics of seismogenic faulting in continental lithosphere( 2020)This thesis explores relationships between the structure, rheology, and rupture properties of seismogenic faulting in continental lithosphere from four different perspectives. First, I derive a scaling relationship that links the spacing between two nearly parallel strike-slip faults to the frictional strength, fault width, and lower crust viscosity for strike-slip shear zones. Based on the scaling law, I estimate a possible range of lower crust viscosity in the San Andreas Fault system (California), the Marlborough Fault Zone (New Zealand) and central Tibet (China). Second, using numerical modelling methods, I explore how lower crust rheology contrast may affect the long-term evolution of a major plate boundary fault. The case study is based on the San Andreas Fault, which is found to vary dipping angles (~50-90 degree) along strike. The moderately dipping strike-slip fault is not consistent with Anderson faulting theory. This inconsistency may be reconciled if there are lateral variations in the lower crustal rheology across the fault plane that decrease fault dip with time. Third, in addition to strike-slip faults in active tectonic settings, my study also includes reverse faults in stable cratonic regions, especially for the cratonic areas of western and southern Australia. I apply statistical methods to investigate the co-seismic slip distribution of 11 surface-rupturing earthquakes in Australian stable regions and provide a link between the shape and characteristics of co-seismic slip distributions and the geophysical properties of the host crust. Fourth, using a comprehensive geophysical survey with the co-located 13GA-EG1 and 12GA-AF3 seismic reflection profiles and magnetotelluric profiles and regional gravity and magnetic maps in the Nullarbor Plain (Australia), I find that faults initiated back to the Proterozoic could still be reactivated in a Cenozoic convergent setting, especially for those major faults cutting to deep crust. Those deep-penetrating faults at terrane boundaries could be a potential channel for fluids to pass through, and thus further weakened by the fluids, which is revealed by high-conductivity anomaly in magnetotelluric profiles. The last research chapter of this thesis addresses a technical issue in the particle-in-cell finite element method, which is widely used in geodynamic numerical modelling. As mixing materials with contrasting viscosity within one element results in stress fluctuations, I assess different smoothing methods to reduce the spurious stress in mixed-material elements.