Rock Magnetism: Magnetic Anisotropy in Olivine Crystals

Olivine is one of the most common minerals on Earth, making up large parts of the mantle. This study will investigate anisotropy of magnetic susceptibility (AMS) in olivine single crystals. We will examine the relation of the AMS to the structure and composition of the crystal and the orientation of possible inclusions. This involves measuring magnetic anisotropy in low and high magnetic fields and at different temperatures in order to separate paramagnetic and ferromagnetic contributions to the magnetic fabric.

Kontakt: Andrea Biedermann   Ann Hirt  

Status: Offen

Professur: Jackson

Secular Variation recorded in Lacustrine Sediments

Lacustrine sediments have been shown to be reliable, high-resolution recorders of the Earth’s magnetic field. This project involves determining the characteristic directions of the remanent magnetization in Holocene lacustrine sediments from Swiss lakes, using standard paleomagnetic techniques. Identification of the ferromagnetic minerals responsible for the paleomagnetic signal will be determined using rock magnetic techniques. Results will be compared with models of the geomagnetic field.

Kontakt: Ann Hirt  

Status: Offen

Professur: Jackson

Interpretation of seismic tomography results

Seismic tomography is the best geophysical tool presently available to image deep earth 3D structure at all scales. Tomographic images are widely used by all earth scientists to cross check their models, though quantitative interpretation of such images demand intimate knowledge of data and methodology and some understanding of standard resolution assessment. The most complete assessment of resolution and reliability of tomographic results in an easy-to-understand way is possible by synthetic data testing for characteristic model structure. With a series of synthetic tests it shall be documented why and how plates in subduction zones in most cases appear to widen with depth and why their velocity anomaly is often two low in combination with a subvertically elongated slab.

Kontakt: Edi Kissling  

Status: Offen

Professur: Giardini

Modelling the evolution of Venus' mantle and lithosphere

Venus is a similar size to Earth, but looks quite different, lacking plate tectonics but having features such as coronae, highlands, and volcanos, and curiously, a surface with a fairly uniform age of ~700 million years. In this project, the evolution of Venus' mantle, lithosphere and crust will be studied using three-dimensional numerical simulations of the coupled system (including crust formation and core evolution), and comparing results to observations of the planet.

Kontakt: Paul Tackley  

Status: Offen

Professur: Tackley

Mantle and lithosphere dynamics in extrasolar Super-Earths

In the last 15 years, hundreds of planets have been found around other stars. A few of these are rocky planets, perhaps similar to Earth but larger. There is intense interest in whether these could harbor life, and an essential ingredient for life is thought to be plate tectonics, which is related to mantle convection. Due to the much higher pressures inside super-Earths, the dynamics might be quite different from in Earth. In this project, numerical simulations of mantle convection and lithosphere dynamics will be performed, in order to understand better key aspects of the dynamics, and make predictions about planets that have been or will be discovered.

Kontakt: Paul Tackley  

Status: Offen

Professur: Tackley

Jupiter's moon Io: Volcanic resurfacing and the distribution of mountains

Io is the most volcanically-active body in the solar system, due to intense heating by tidal dissipation. This heat is transported from the interior to the surface by some mixture of melt migration and solid-state convection, but this is poorly understood. In this project, the processes of uneven magmatic resurfacing and the resulting stresses that cause mountains to form will be studies using numerical simulations in 2-D and 3-D.

Kontakt: Paul Tackley  

Status: Offen

Professur: Tackley

Slab graveyards at the core-mantle boundary

Most slabs appear to sink to the bottom of the mantle, where they are heated up by the core, their chemically-distinct components (crust and residue) may segregate, they may cause the formation up upwelling hot plumes, and they interact with the post-perovskite phase transition. High-resolution three-dimensional numerical models will be used to study these processes and the results will be related to detailed seismic studies.

Kontakt: Paul Tackley  

Status: Offen

Professur: Tackley

Plate interaction in New Zealand using 3D numerical modelling

The southern island of New Zealand sits at the boundary of the Australian and Pacific plates. The relative plate motion is well constrained, but where exactly it takes place is still a mystery. Is it completely localized along the Alpine Fault, which is considered to be the "official" plate boundary? Or is it distributed within the plates themselves? How do the crust and lithospheric mantle behave in the proximity of the plates boundary? The project involves addressing these questions by setting, running, and analyzing numerical simulations using a 3D numerical model.

Kontakt: Taras Gerya  

Status: Offen

Professur: Tackley

Rifting, transforms and localized volcanism in young oceanic lithosphere

Using existing 3-D numerical models of oceanic spreading initiation compared to the natural data the Terceira ultra-slow rift in the Azores will be investigated. Main goal is to understand rift asymmetry and distribution of volcanic islands inside the rift.

Kontakt: Taras Gerya  

Status: Offen

Professur: Tackley

3-D dynamics of subduction and crustal growth in magmatic arcs

3-D numerical experiments simulating subduction of an oceanic plate under a continent will be performed with the use of existing numerical models. Variations in slab geometry, continental margin topography, magmatic arc productivity and back-arc extension will be studied as a function of various physical parameters.

Kontakt: Taras Gerya  

Status: Offen

Professur: Tackley

3-D dynamics of slab breakoff

3-D numerical experiments simulating breakoff of a subducted oceanic plate in the beginning of continental collision will be performed with the use of existing numerical models. Variations in breakoff dynamics, surface topography development and subducted crust melting will be studied as a function of slab age, geometry, composition and subduction rate. Numerical results will be tested on the data from Mediterranean region.

Kontakt: Taras Gerya  

Status: Offen

Professur: Tackley

Sedimentary basin development

2-D and 3-D numerical experiments simulating development of a sedimentary basin on a continental lithosphere will be performed with the use of existing numerical models. Variations in basin development dynamics will be studied as a function of continental crust structure and composition and lithospheric extension velocity.

Kontakt: Taras Gerya  

Status: Offen

Professur: Tackley

Emplacement of large multi-phase intrusions (batholiths) in magmatic arcs

2-D and 3-D numerical experiments simulating intrusion of partially crystallized magmas from sub-lithospheric depths into the crust of a volcanic arc will be performed with the use of existing numerical models. Variations in intrusion geometry and dynamics will be studied as a function of variable magma volume, composition and viscosity.

Kontakt: Taras Gerya  

Status: Offen

Professur: Tackley

Kimberlitic pipes emplacement into the continental crust

2-D and 3-D numerical experiments simulating intrusion of kimberlitic pipes from depths of 200-300 km to the near-surface region of the continental crust will be performed with the use of existing numerical models. Variations in intrusion geometry, size and dynamics will be studied as a function of variable kimberlitic magma volume and viscosity.

Kontakt: Taras Gerya  

Status: Offen

Professur: Tackley

Emplacement and evolution of the World´s largest Bushveld layered intrusion

2-D and 3-D numerical experiments simulating emplacement of the World´s largest Bushveld layered intrusion ("magmatic sea" - 300 km in diameter, 8 km deep magma chamber) will be performed with the use of existing numerical models. Variations in intrusion internal structure and dynamics will be studied as a function of variable magma volume and viscosity.

Kontakt: Taras Gerya  

Status: Offen

Professur: Tackley

Iron core formation of terrestrial planets

3-D numerical experiments simulating planetary tectonic processes during iron core formation will be performed with the use of existing numerical models. Variations in planetary reshaping dynamics will be studied as a function of variable structure and size of the body.

Kontakt: Taras Gerya   Gregor Golabek  

Status: Offen

Professur: Tackley

Formation of Artemis Corona by impact-induced subduction

Artemis Corona is an enigmatic structure on Venus. With 2600 km diameter it is one of the dominating surface features and has been interpreted to be the site of plate tectonics operating on a regional scale. In this study you will use the 3D finite difference code I3VIS to explore the hypothesis whether an impact event might have triggered subduction on Venus resulting in the formation of Artemis Corona.

Kontakt: Taras Gerya   Gregor Golabek  

Status: Offen

Professur: Tackley

Free numerical modeling project

Do you have your own ideas what planetary / geodynamic / tectonic / geological / deformation / thermal / etc. process you want to model and understand? Then you can define the content of your own project and use existing advanced 2-D and 3-D thermomechanical codes for satisfying your curiosity and investigating your own scientific problem.

Kontakt: Taras Gerya  

Status: Offen

Professur: Tackley

Influences of surface processes on planetary scale tectonics and convection

The dynamics of the mantle, lithosphere and the evolution of the Earth's landscape, are without doubt, intimately coupled over geodynamic time scales. The apparentness of these observations has largely been demonstrated via numerous numerical studies and confirmed by field based studies. In the context of mountain belt formation and geodynamic stability of plate boundaries, the nature and strength of the coupling between the atmosphere, and the mantle-lithosphere has long been debated. Unravelling whether climate promotes mountain growth, or vice versa, remains an enigmatic question in geodynamics. In this project we will develop a new 2D numerical model to study the effect of this coupling and to determine its importance on planetary scale convection.

Kontakt: Dave May  

Status: Offen

Professur: Tackley

Scalability of massively parallel, multilevel preconditioning strategies

In this project we will study the parallel performance characteristics of a number of multilevel preconditioning strategies accessible through the PETSc (Portable Extensible Toolkit for Scientific computation) on Brutus. Preconditioning strategies will include additive Schwarz method (ASM) geometric multrigrid (GMG) and various implementations of algebraic multigrid (AMG). Target applications will involve localisation problems originating from models of lithospheric deformation.

Kontakt: Dave May  

Status: Offen

Professur: Tackley

Studying non-linear solution strategies for solving Stokes flow problems with visco-plastic rheologies

The study of shear banding and faulting behaviour in rocks is of fundamental importance in geodynamics. Numerically, the inclusion of brittle like behaviour is realised through a non-linear, visco-plastic rheology. In such models, shear bands manifest themselves as emergent structures characterised by localised channels of low viscosity, thus making the efficient numerical solution a challenging problem. In this project, we will examine using different non-linear solution techniques such as Picard method, modern variants of Newtons method and pseudo transient continuation. The outcome of this project is to develop a robust, efficient and optimal solution strategy for the non-linear Stokes flow.

Kontakt: Dave May  

Status: Offen

Professur: Tackley

Exploring alternative finite element (FE) discretisations for Stokes flow

Classical FE approaches for Stokes flow typically pose the viscous flow problem in terms of velocity and pressure. Alternatives exists in which either the stress or strain-rate is an independent unknown. Such formulations have advantages for the non-linear rheologies encountered in geodynamics. We will explore the use of such formulations used in conjunction with variable viscosity Stokes flow. We are interested in establishing the accuracy of the approach and in developing robust preconditioning strategies for the resulting discrete set of equations.

Kontakt: Dave May  

Status: Offen

Professur: Tackley

Code generation techniques for the rapid development of geodynamic finite element software

Automatically code generation offers many advantages of traditional programming methods. Recently, a number of powerful tools have been made available to generate code for finite element computations. Specifically, they enable variational forms to be transformed directly into functions which evaluate the element stiffness matrices. In this project, we wish to incorporate these software concepts into a high performance finite element geodynamics package which will enable rapid prototyping of alternative continuum descriptions for rocks and related geomaterials.

Kontakt: Dave May  

Status: Offen

Professur: Tackley

Development of a parallel CPU-GPU based material point method for studying geodynamic processes

GPU's represent significantly faster computational units than CPU's for certain types of inherently parallel operations. The modern hardware used in today's supercomputers typically employ CPU's with access to GPU like processors. Combining the classical parallelism possible via MPI between CPU's and that available on the GPU hardware offers the potential for very efficient finite element and finite difference software. In this project we will explore this area of research.

Kontakt: Dave May  

Status: Offen

Professur: Tackley

A fully unstructured, particle-in-cell (PIC) finite element (FE) method for computational geodynamics

In geodynamics, researchers have traditionally either tried to employ full Lagrangian, unstructured grid discretisations or combined particle methods with structured grid discretisations. The former approach suffers from a loss of accuracy due to the mapping of material state variables from one grid to another, whilst the latter suffers from inadequate grid resolution in regions of high deformation. In this project, we combine the positives of both approaches by tracking material histories with Lagrangian particles, combined with an unstructured finite element grid to study free surface processes and lithospheric deformation.

Kontakt: Dave May  

Status: Offen

Professur: Tackley

The effect of initial thermal structure on patterns of mantle convection

Most models of mantle convection use laterally homogeneous thermal initial conditions. Yet, recent models on the modes of planetary core formation indicate that the initial thermal structure of a planet could be strongly asymmetric. Here, you will therefore study the effects of the laterally inhomogeneous temperature-distributions on convection with a special focus on the resulting stress-conditions in the upper mantle and lithosphere that could lead to spontaneous subduction initiation, a vital ingredient to the general theory of self-consistent plate tectonics that is still largely unresolved today.

Kontakt: Gregor Golabek  

Status: Offen

Professur: Tackley

Numerical modelling of coronae formation on Venus

Coronae are enigmatic circular features on the surface of Venus, for which a number of creation mechanisms have been proposed. Yet, few of these models have been tested quantitatively. Here, you will use a viscoelastoplastic finite element code to study the possibility that Venus coronae have been formed by a plume impinging on the lithosphere. The models will include a parametrized melting model as well as a free surface, and will be compared with simpler semi-analytical models in order to obtain a deeper insight in the underlying physics.

Kontakt: Gregor Golabek  

Status: Offen

Professur: Tackley

Survival of a chondritic surface layer on asteroids

Primitive meteorites dating back to the start of the solar system show that iron and silicates were initially mixed on a small-scale. This so-called chondritic composition is normally destroyed during the iron-silicate separation. However recent 1D studies suggest that close to the surface such a chondritic surface layer could avoid melting and survive until present day. In this study you will use 2D numerical models including a parametrized melting model for chondritic material to study the conditions under which such a chondritic shell can avoid its destruction.

Kontakt: Gregor Golabek  

Status: Offen

Professur: Tackley

The Ganymede-Callisto dichotomy

The two largest and most massive moons of Jupiter, Ganymede and Callisto exhibit very different internal structures. Ganymede is differentiated into iron core, silicate and ice mantle. It shows signs of past geological activity and has until present an internal magnetic field. Callisto on the other hand seems to be undifferentiated and shows an ancient, heavily cratered surface with no sign of geological activity. In this project you will apply 2D numerical models to study the early internal evolution of these two moons. The results will be used to derive constraints on the formation conditions of Ganymede and Callisto, which will help to better understand why they followed different evolutionary paths.

Kontakt: Gregor Golabek  

Status: Offen

Professur: Tackley

Investigation of magnetic traits of sand dunes in SW Africa

The mineral-magnetic compositions of sand samples collected along the Pacific coast of Namibia and Angola will be investigated by hysteresis and susceptibility measurements between room temperature and 700°C. The thermal variation of the magnetic pattern of the samples provides information about the magnetic carriers and their source areas. Knowing the source areas is a key to deduce eolian transport mechanism during desertification. In combination with published climate information these data will be used to reconstruct the development of the Namibian Sand Sea since early Miocene. This project addresses students with interests in geophysical experiments in the context of the broad field of landscape development.

Kontakt: Andreas Gehring  

Status: Offen

Professur: Jackson

Archaeomagnetism of a metallurgical kiln from Korsimoro, Burkina Faso

The geomagnetic field evolution during the past Millennia in the Southern Hemisphere is poorly known. This project aims providing new archaeomagnetic data from a well burned structure belonging to a metallurgical site in Burkina Faso. Standard archaeomagnetic techniques will be used to determine the directions of the ancient field, and rock magnetic measurements will be performed to check the quality of the magnetic minerals in the samples. The results will be compared with the available global geomagnetic field models, and will serve to refine them.

Kontakt: Fabio Donadini  

Status: Offen

Professur: Jackson

Long-period magnetotellurics at Watheroo observatory

A unique dataset of electric and magnetic field measurements from the 1930s will be used to infer electrical properties of the crust and mantle. The student will learn to process such data and learn strategies to solve the non-linear inverse problem of electromagnetic induction in a 1-D Earth. The long time series is probably capable of detecting electrical conductivies down to the core. Comparisons will be made with inferences of conductivity available from modern satllite measurements.

Kontakt: Alexey Kuvshinov   Andrew Jackson  

Status: Offen

Professur: Jackson

Experimental investigation of water ice crystallization under turbulent flow conditions. Implication for Titan and Europa Ice shell geometry.

It has been suggested that forced longitudinal librations (small periodic fluctuations of the planet rotation rate) can generate turbulence near the outer boundary of the subsurface ocean of Europa and Titan. The proposed experiment consists of a channel flow laboratory setup with a cooling system at the bottom surface. The strength of the flow (the Reynolds number) and the Heat flux at the bottom will be the two control parameters in the system. The goal of the study will be to determine how the growth rate of the bottom layer of ice varies with the Reynolds number. The diagnostic techniques will include, acoustic doppler velocimetry, particles tracking, pressure and temperature measurements. This project could be continued as a Phd. Several orientations will then be possible including some theoretical analysis as well as numerical simulations coupled to the experiments.

Kontakt: Jérôme Noir  

Status: Offen

Professur: Jackson

Recovery of mantle conductivity structures in a presence of non-uniform oceans

It is known that non-uniform oceans significantly distort the results of interpretation of global induction data in many regions of the world. To account for the ocean effect, a simple but approximate three-dimensional (3-D) correction scheme is usually exploited. In this project the student will test a new interpretational scheme, which is based on rigorous 1-D inversion of the data in the framework of a 3-D model with non-uniform oceans.

Kontakt: Alexey Kuvshinov  

Status: Offen

Professur: Jackson

Magnetostratigraphy in the Lower Triassic

The pattern of magnetic reversals is not well documented for the Lower Triassic. This project involves isolating the characteristic remanent magnetization of sediments from the Nanmal Gorge in the Salt Range, Pakistan in order to obtain a magnetostratigraphic record for correlation.

Kontakt: Ann Hirt  

Status: Offen

Professur: Jackson

Enviromagnetics as a Climate Proxy in Swiss Lakes

The magnetic properties of lake sediments are strongly dependent on the iron phases that are present. The type and concentration of iron phases is closely linked to environmental conditions in the lake and catchment basin. This project will examine magnetic properties of sediments from cores in Soppensee.

Kontakt: Ann Hirt  

Status: Offen

Professur: Jackson

two-station seismology in Europe and the Mediterranean basin

The student will make use of existing software to analyze earthquake data recorded at pairs of stations in the Western Mediterranean and Europe. Comparison (cross-correlation) of surface waves associated with the same event and recorded at two stations provides information about crust-to-upper mantle structure between the two stations. This allows high-resolution imaging of the lithosphere-asthenosphere boundary region. New data associated with the new Italian broadband network, the Orpheus database and temporary deployments in Northern Africa, Iberia and the Western Mediterranean will be analyzed. Implications for our understanding of topography and mantle flow in the area of interest will be explored. References: Boschi, L. and T. W. Becker, GRL 38, L20306, 2011. Meier, T. et al., GJI 156, 45--58, 2004.

Kontakt: Lapo Boschi  

Status: Offen

Professur: Giardini

Seismology without earthquakes: attenuation

Seismic interferometry allows us to measure seismic waves generated by the Earth's microseismic noise, and to use these data for seismic imaging, or for monitoring active faults and volcanoes. Today we are able to use this approach to identify and use the phase of surface waves (and, in some cases, body waves), but their amplitude is more difficult to measure: it is not even clear whether it can be measured at all. The student will build on the work of Boschi et al. (http://www.seg2.ethz.ch/boschil/bwvezg12.pdf), describing the amplitude problem in a ray-theory formulation. Application to real Earth data will shed light on the attenuation properties of crust and lithosphere.

Kontakt: Lapo Boschi  

Status: Offen

Professur: Giardini

The internal structure of the Moon

The internal structure and composition of a planet or satellite are important constraints on theories for how such bodies formed and evolved. Of all geophysical methods used to study a planet's structure, seismology is uniquely suited to determine many of the parameters that are critically important to understand the dynamic behaviour of the planet. For this reason seismology has played a leading role in the study of the internal structure of the Earth. The only other solar system body from which we have seismic observations pertinent to its interior properties is the Moon, thus giving us an opportunity to examine planetary formation in general without being tied to the Earth. The aim of this project will be to invert seismic data from the Moon acquired during the Apollo missions. The data set that will be considered has been significantly improved and expanded upon relative to what available during the Apollo era and thereafter.

Kontakt: Amir Khan  

Status: Offen

Professur: Jackson

Using electromagnetic souding data to investigate water content of the lunar mantle

The currently favoured theory for the origin of the Moon involves a collision in the late stages of planetary formation between the proto-Earth and a Mars-sized impactor having a substantial fraction of the proto-Earth mass. Modeling studies show that a proportion of the mantle material ejected by the impact would settle in a ring around the Earth from which the Moon would accrete. This scenario involves a high temperature origin for the Moon as a result of which it is believed that water and other volatiles would have been vaporized resulting in a bone-dry Moon. In this project we would like to investigate this in more detail by inverting electromagnetic sounding data acquired during the Apollo missions. To invert for mantle water content we will make use of laboratory-based electrical conductivity profiles that are obtained though mantle mineral phase equilibrium computations.

Kontakt: Amir Khan  

Status: Offen

Professur: Jackson

Inversion of magnetic transfer functions in a presence of 3-D subsurface inhomogeneities

It was demonstrated recently that magnetic transfer functions (tippers) at coastal and island geomagnetic observatories - being large due to ocean effect - are sensitive to crustal one-dimensional geoelectric structures beneath the oceanic layer and thus can be used to probe the crust. This, in particular, means that the large amount of data that were not exploited for induction studies so far can be reconsidered as useful source of information at many observatories. The objective of the project is to elaborate numerical inverse solution to recover crustal conductivity from the observed tippers. The student will learn: a) to estimate transfer functions from geomagnetic data; b) to program in Matlab and FORTRAN; c) to work with the code which calculates electromagnetic fields in Cartesian models with three-dimensional electrical conductivity distribution; d) to apply gradient type optimization schemes for inverting magnetic transfer functions. The developed inverse solution will be used for analysis of real observatory geomagnetic data. Ultimately comparisons will be made between crustal conductivity profiles obtained in different regions of the world.

Kontakt: Kuvshinov Alexey  

Status: Offen

Professur: Jackson

Explaining observed magnetic signals from intense lightnings

Unique magnetic field data in 4 Hz - 1 kHz frequency band have been recorded in 2009 by four high precision magnetometers around the world with the aim to study and monitor intense lightnings. Comparison of the observed waveforms with those predicted by simplified models of the Earth-ionosphere cavity reveals substantial discrepancy between observations and predictions. The objective of the project is to estimate the influence of the actual conductivity distributions on the observed magnetic waveforms. The distributions of interest are the day/night asymmetry of the ionosphere conductivity, the polar cap asymmetry, and the inhomogeneities of the Earth's surface layer due to nonuniform distribution of conductive oceans and resistive continents. The student will learn: a) to perform time series analysis of the geomagnetic data; b) to program in Matlab and FORTRAN; c) to work with (and modify) the code which calculates high-frequency electromagnetic fields in spherical models with 3-D electrical conductivity distribution; d) to understand and program fundamental solutions of Maxwell's equations in radially-symmetric models of the Earth.

Kontakt: Alexey Kuvshinov  

Status: Offen

Professur: Jackson

Mapping electrical conductivity in the Earth's mantle using ocean tidal EM fields

Recent laboratory experiments demonstrate that electrical conductivity of upper mantle (UM) minerals is greatly influenced by small amounts of water or by partial melt. Determination of deep conductivity using electromagnetic (EM) methods can thus provide information on the presence of volatiles and melting processes in UM. Probing conductivity at UM depths requires EM data with periods between a few hours and one day. This is a challenging period range for EM studies due to the spatially complex ionospheric source that prevails at these periods. The objective of the project is to investigate a possibility to exploit alternative large scale EM source to probe UM: electric currents induced by ocean tidal flows in the Earth's main magnetic field. The student will analyze coastal and sea bottom data collected in North Pacific Ocean region, and then will combine these data with three-dimensional (3-D) tidal simulations to invert for UM electrical structure. The student will learn: a) to process EM data in order to estimate amplitudes and phases of specified set of tidal lines; b) to program in Matlab and FORTRAN; c) to work with the codes which calculate EM fields in spherical and Cartesian models with 3-D electrical conductivity distribution; d) to apply optimization schemes for inverting these EM data.

Kontakt: Alexey Kuvshinov  

Status: Offen

Professur: Jackson