Louis Moresi

Australian National University | ANU · Research School of Earth Sciences

Subduction zones become congested when they try to consume buoyant, exotic crust. The accretionary mountain belts (orogens) that form at these convergent plate margins have been the principal sites of lateral continental growth through Earth's history. Modern examples of accretionary margins are the North American Cordilleras and southwest Pacific...

(2D) and three-dimensional (3D) simulations are used to explore the effects of continental distribution on mantle convection. In both 2D and 3D, at total surface areas < 50%, internal temperature is weakly sensitive to continental configuration. Mantle heat flux values show mild variations with changing configuration. In 3D, at total continental ar...

The geological record and seismic tomography together contain multiple examples of mantle plumes and subducting oceanic slabs interacting, however consequences of these interactions and a mechanism for plumes to pass from the subducting to the overriding plate are uncertain. We present three-dimensional numerical simulations of a retreating subduct...

We outline a mathematical formulation for mantle convection which can deal with the viscoelastic–plastic rheology of the cool parts of the lithosphere. This formulation is then analyzed to expose the numerical challenges inherent in the equations and a suitable solution strategy is outlined. With this strategy in place, we discuss a parallel implem...

To what extent mechanical anisotropy is required to explain the dynamics of the lithosphere is an important yet unresolved question. If anisotropy affects stress and deformation, and hence processes such as fault loading, how can we quantify its role from observations? Here, we derive analytical solutions and build a theoretical framework to explor...

Despite considerable progress in seismology, mineral physics, geodynamics, paleomagnetism, and mathematical geophysics, Earth’s inner core structure and evolution remain enigmatic. One of the most significant issues is its thermal history and the current thermal state. Several hypotheses involving a thermally-convecting inner core have been propose...

The Pacific Plate underwent a significant change in motion during the early Eocene. This change has been linked to plate boundary reconfiguration, particularly in relation to subduction margins. The reconfiguration also resulted in a new Pacific‐Australian plate boundary section transecting Zealandia. Following the Eocene transition, the relative r...

Visco‐elastic‐plastic modeling approaches for long‐term tectonic deformation assume that co‐seismic fault displacement can be integrated over 1000s–10,000s years (tens of earthquake cycles) with the appropriate failure law, and that short‐timescale fluctuations in the stress field due to individual earthquakes have no effect on long‐term behavior....

The interplay between climate-forced sea-level change, sediment erosion and deposition, and flexural adjustments in deep time on passive margin deltas remains poorly understood. We performed a series of conceptual simulations to investigate flexural isostatic responses to high-frequency fluctuations in water and sediment load associated with climat...

Dynamics of Plate Tectonics and Mantle Convection, written by specialists in the field, gathers state-of-the-art perspectives on the dynamics of plate tectonics and mantle convection. Plate tectonics is a unifying theory of solid Earth sciences. In its initial form, it was a kinematic theory that described how the planet’s surface is fragmented int...

Visco-elastic-plastic modelling approaches for long-term tectonic deformation assume that co-seismic fault displacement can be integrated over 1,000s-10,000s years (tens of earthquake cycles) with the appropriate failure law, and that short-timescale fluctuations in the stress field due to individual earthquakes have no effect on long-term behavior...

Numerical models have become an indispensable tool for understanding and predicting the flow of ice sheets and glaciers. Here we present the full-Stokes software package Underworld to the glaciological community. The code is already well established in simulating complex geodynamic systems. Advantages for glaciology are that it provides a full-Stok...

We investigate how the mechanical properties of intra-oceanic arcs affect the collision styleand associated stress-strain evolution with buoyancy-driven models of subduction that accurately reproducethe dynamic interaction of the lithosphere and mantle. We performed a series of simulations only varyingthe effective arc thickness as it controls the...

The Cenozoic landscape evolution in southwestern North America is ascribed to crustal isostasy, dynamic topography, or lithosphere tectonics, but their relative contributions remain controversial. Here we reconstruct landscape history since the late Eocene by investigating the interplay between mantle convection, lithosphere dynamics, climate, and...

Numerical models have become an indispensable tool for understanding and predicting the flow of ice sheets and glaciers. Here we present the full-Stokes software package Underworld to the glaciological community. The code is already well established in simulating complex geodynamic systems. Advantages for glaciology are that it provides a full-Stok...

The San Andreas fault (California, USA) is near vertical at shallow (<10 km) depth. Geophysical surveys along the San Andreas fault reveal that, at depths of 10-20 km, it dips ∼50-70° to the southwest near the Western Transverse Ranges and dips northeast in the San Gorgonio region. We investigate the possible origin of along-strike geometric variat...

Numerical models of groundwater flow play a critical role for water management scenarios under climate extremes. Large-scale models play a key role in determining long range flow pathways from continental interiors to the oceans, yet struggle to simulate the local flow patterns offered by small-scale models. We have developed a highly scalable nume...

The Earth's paleo-climate record indicates climate fluctuations, from cool to warm to cool conditions, over the last ~300 My. Over that time, the Earth's most recent super-continent, Pangea, formed and broke apart. Data constraints together with numerical models indicate that Pangea formation and breakup affected spatial and temporal patterns of he...

The San Andreas Fault (SAF) is one of the dominant components of the transform boundary between the Pacific and the North American Plate. Although the fault is vertical- to sub-vertical at shallow (<10 km) depth, it variably dips at angles of ca. 40-70º to the south-west near the western Transverse Range and to the northeast in its southern segment...

Arc-continent collision is the process by which intra-oceanic arc crust is accreted to continental margins and the most important mechanism that enables the growth of the continental crust since Phanerozoic times. We use numerical visco-plastic mechanical models to explore how crustal-mantle dynamics control the evolution of the stress regime in co...

The particle-in-cell Finite Element (PIC-FE) method has been widely used in geodynamic numerical modelling due to its efficiency in dealing with large deformations without the requirement of remeshing. However, material deformation within a Eulerian mesh frame will mix particles of contrasting strength properties (e.g., viscosity in Stokes problems...

The particle-in-cell Finite Element (PIC-FE) method has been widely used in geodynamic numerical modelling due to its efficiency in dealing with large deformations without the requirement of remeshing. However, material deformation within a Eulerian mesh frame will mix particles of contrasting strength properties (e.g., viscosity in Stokes problems...

Cratons are ancient regions of relatively stable continental fragments considered to have attained long‐term tectonic and geomorphic stability. Low‐temperature thermochronology data, however, suggest that some cratons have experienced discrete Phanerozoic heating and cooling episodes. We report apatite fission track, and apatite and zircon (U‐Th)/H...

Earthquake moment tensors in eastern Pacific (ePac) slabs typically show downdip tensional (DT) axes, whereas in the western Pacific (wPac), they typically show downdip compressional (DC) axes or have mixed orientations indicative of unbending. Prevailing conceptual models emphasize uniform stress/deformation modes, that is, bulk slab stretching or...

Human activity causes vibrations that propagate into the ground as high-frequency seismic waves. Measures to mitigate the COVID-19 pandemic caused widespread changes in human activity, leading to a months-long reduction in seismic noise of up to 50%. The 2020 seismic noise quiet period is the longest and most prominent global anthropogenic seismic...

The interelement stress in the Finite Element Method is not continuous in nature, and stress projections from quadrature points to mesh nodes often causes oscillations. The widely used particle-in-cell method cannot avoid this issue and produces worse results when there are mixing materials of large strength (e.g., viscosity in Stokes problems) con...

Gaps within a subducting plate can alter the surrounding mantle flow field and the overall subduction zone dynamics by allowing hot sub-slab mantle to flow through the gaps and into the mantle wedge. This through-slab flow can produce melting of the slab gap edges as well as significant upwelling that can lead to anomalous alkaline volcanism and/or...

This paper outlines a Finite Element modelling workflow using the software package ‘Underworld’ that is applied to sedimentary basin undergoing multiple rifting events. The evolution of the resulting strain rate, viscosity structure, temperature field, and sedimentary structures can be tracked. Application to the Ceduna Sub-basin is discussed.

The relationship between intraslab seismicity and the dynamics of subduction is a subject of ongoing debate. Uncertainty surrounds (1) the extent to which the stress regime associated with slab earthquakes reflects the driving/resisting forces of subduction, or more localised processes such as metamorphic or thermo-elastic volume change, and (2) th...

Plain Language Summary Plate tectonics relies on the concept of a rigid surface layer (the lithosphere) fragmented in a series of major and minor tectonic plates moving over a weaker and buoyant layer of asthenospheric material. The motion and deformation of the lithosphere are primarily driven by the sinking of the colder and denser oceanic lithos...

The provenance of Paleozoic and Mesozoic sedimentary sequences in Western Australia remains controversial. Better understanding of sediment provenance has implications for the characterisation of reservoir quality and potential correlation between known reservoirs and reservoirs yet to be discovered. Here, we compare U-Pb zircon chronology and Hf i...

East Pacific (ePac) slabs are characterised by downdip tension (DT) at intermediate depths, whereas most west Pacific (wPac) slabs are dominated by downdip compression (DC, e.g. Tonga) or have mixed mechanisms indicative of unbending (e.g. Kuriles). In this study we argue that despite these contrasts, flexural modes associated with slab bending/unb...

Strike-slip shear zones with sub-parallel arrays of evenly-spaced faults are widely observed in nature, but the controls on the spacing between major faults are unclear. We analyze a 2-D model and develop a scaling law relating the fault spacing to structural and rheological parameters in the continental crust. We find that fault spacing positively...

The variation of temperature in the crust is difficult to quantify due to the sparsity of surface heat flow observations and lack of measurements on the thermal properties of rocks at depth. We examine the degree to which the thermal structure of the crust can be constrained from Curie depth and surface heat flow data in Southeastern Australia. We...

Numerical subduction models often implement an entrained weak layer (WL) to facilitate decoupling of the slab and upper plate. This approach is attractive in its simplicity, and can provide stable, asymmetric subduction systems that persist for many tens of millions of years. In this study we undertake a methodological analysis of the WL approach,...

Since 2006, NCRIS projects (AuScope, NCI, ANDS, Nectar, RDS), and Government Agencies (GA, State/Territory Geological Surveys) have collaborated on building a suite of data portals, tools, software and virtual laboratories to support a diverse community of Earth scientists operating on a range of computational facilities including HPC, cloud, on-pr...

East Asia and South America have both experienced long-term subduction since at least the Jurassic, but they have had contrasting tectonic evolutions since the Late Cretaceous. East Asia was dominated by extensional tectonics with many marginal sea basins forming during the Cenozoic while South America was dominated by compressional tectonics build...

Few modern sediment dispersal pathways predate the breakup of Pangea. This suggests that river lifespan can be controlled by continental assembly and dispersal cycles, with the longest-lived river systems present during supercontinent regimes. Based on the strikingly similar age spectra and Hf isotopic array extracted from Paleozoic to early Mesozo...

Plain Language Summary In subduction zones, one tectonic plate plunges beneath another into the Earth's interior. Some of the earthquakes that occur at subduction zones are unusual due to their occurrence at depths of 70 to 300 km (intermediate depths), deeper than the expected limit of brittle failure. In this study, we evaluate whether the faults...

This study focuses on methodological issues related to dynamic subduction zone modelling. Numerical models often employ an entrained weak layer (WL approach) to facilitate decoupling between the subducting and overriding plates. In such a setup, the kinematics of the flow lead to width variations in the subduction interface. When a uniform-width in...

The fluvio-deltaic Triassic Mungaroo Formation, North West Shelf (NWS) of Australia, hosts vast resources of hydrocarbons. However, the mechanisms that generated its 4-6 km monotonous infill architecture (colloquially known as layer cake stratigraphy) remain elusive. The vertical fluctuation between fluvial and shallow marine deposits indicates tha...

The processes involved in the structural and stratigraphic evolution of the North West Shelf (NWS), one of the most productive and prospective hydrocarbon provinces in Australia, remain controversial. The complex structural characteristics of the NWS include large-scale extensional detachments, difference between amounts of crustal and lithospheric...

We present a series of Moho depth maps for the Alaskan region based on P receiver function estimates using data from all available broadband instrumentation from 1999 to April 2018 including the USArray Transportable Array. The average Moho depths beneath individual broadband stations are presented first as spot measurements and then used to produc...

Spherical harmonic expansion of the residual topography with both ships-track and precise pointwise data used.

spherical harmonic expansion (degree 0-30) of the residual topography with both ship-track and precise point-wise data used.

recovered long-wavelength (degree 0-3) residual topography with both ship-track and precise point-wise data used.

These slides show that when the ship-track data with crude sediments and crustal thickness corrections compensate the precise but scarce point-wise data, the recoverred long-wavelength residual topography still has a large amplitude.

The CO2 liberated along subduction zones through intrusive/extrusive magmatic activity and the resulting active and diffuse outgassing influences global atmospheric CO2. However, when melts derived from subduc- tion zones intersect buried carbonate platforms, decarbonation reactions may cause the contribution to atmospheric CO2 to be far greater th...

The CO2 liberated along subduction zones through intrusive/extrusive magmatic activity and the resulting active and diffuse outgassing influences global atmospheric CO2. However, when melts derived from subduction zones intersect buried carbonate platforms, decarbonation reactions may cause the contribution to atmospheric CO2 to be far greater than...

Some seismic models derived from tomographic studies indicate elevated shear‐wave velocities (≥4.7 km/s) around 120‐150 km depth in cratonic lithospheric mantle. These velocities are higher than those of cratonic peridotites, even assuming a cold cratonic geotherm (i.e., 35 mW/m2 surface heat flux) and accounting for compositional heterogeneity in...

Recent tomographic studies have imaged an increasing number of discontinuities, gaps, or holes in subducting slabs, which can range in size from one to several hundreds of kilometers and commonly occur in proximity to alkaline volcanism. Studies of slab detachment suggest vertical advection of subslab asthenosphere can occur through slab gaps or ho...

Earth's oldest near-surface material, the cratonic crust, is typically underlain by thick lithosphere (>200 km) of Archean age. This cratonic lithosphere likely thickened in a high-compressional-stress environment, potentially linked to the onset of crustal shortening in the Neoarchean. Mantle convection in the hotter Archean Earth would have impar...

Northeast Asia underwent widespread rifting and magmatic events during the Cenozoic. The geodynamic origins of these tectonic events are often linked to the Pacific plate subduction beneath Northeast Asia. However, the Japan Sea did not open until the late Oligocene, that is, tens of millions of years after the Pacific Plate subduction initiation i...

Northeast Asia underwent widespread rifting and magmatic events during the Cenozoic. The geodynamic origins of these tectonic events are often linked to Pacific plate subduction beneath Northeast Asia. However, the Japan Sea did not open until the late Oligocene, tens of millions of years after Pacific Plate subduction initiation in the Paleocene....

Continental rifting precedes the breakup of continents, leading to the formation of passive margins and oceanic lithosphere. Although rifting dynamics is classically described in terms of either active rifting caused by active mantle upwelling, or passive rifting caused by far-field extensional stresses, it was proposed that a transition from passi...

Large-scale detachment of subducting slabs can have a significant geologic footprint by altering the slab-driven mantle flow field as hot subslab mantle can flow upward through the newly developed opening in the slab. The resulting increase in heat and vertical motion in the mantle wedge may contribute to volcanism and broad surface uplift. Recent...