Research

Normal modes and Earth's inner core

w/ Arwen Deuss (Utrecht University), Olivia Walbert (Princeton University), Jeroen Tromp (Princeton University), Hen Brett (TNO)

Earth's normal modes and the ways in which they 'split' are observables for studying Earth's internal structure. In particular my research focusses on studying the anisotropy, or directional dependence, of material properties in Earth's inner core. This includes development of novel software, NMSplit90, to compute normal-mode splitting effects due to tilted, transverse anisotropy, as well as a transdimensional Bayesian MCMC toolkit for inverting the interior structure.

Elasto-gravitational simulations with SPECFEM

w/ Jeroen Tromp (Princeton University), Hom Nath Gharti (Queen's University)

Modelling Earth's gravitational potential field is of significant interest for both geodynamic forward and inverse problems. The fact that potential fields, unlike other fields such as displacement, are non-zero outside of a body has provided a challenge for numerical modelling as infinite space can not be meshed. This has placed limitations on numerical modelling of geodynamic processes occurring over long timescales which require consideration of gravitational forces.

SPECFEM-X, developed by Hom Nath Gharti and Jeroen Tromp, incorporates gravitational potential fields into SPECFEM-GLOBE using a spectral infinite-element method to solve the Laplace equation in an unbounded spatial domain (see Gharti et al 2018). This refinement enables modelling of 3D quasi-static and elastic problems involving all the features of SPECFEM-GLOBE, but with the additional capability to accurately model spatio-temporal changes to the gravitational field.

My research involves utilising this new toolkit to simulate prompt elasto-gravitational signals (PEGS), Earth's nutations and wobbles, as well as visco-elastic modelling of sea-level change. This work was published in Geophysical Journal International, and can be found here.

Click here for PEGS sensitivity kernels, and here for Prompt Gravity-Strain signals (PGSS) sensitivity kernels. .

Seismic scattering and wavefield diffusivity

w/ Tarje Nissen-Meyer (University of Exeter)

Seismic-wave scattering is observed, to variable degrees of strength, on all planetary bodies for which seismic records exist (e.g. from the InSight and Apollo missions). Global-scale imaging using scattered wavefields is capable of resolving structure orders-of-magnitude smaller than is possible using traditional inversion methods such as tomography. Current scattering models and analytical methods are limited to two end-member phenomena: weak single- or multiple-scattering events (ballistic), or intense scattering such that the wavefield retains no phase information (diffuse). My research explores the existence of scattering behaviour intermediate between these end-members, and the dominant properties of heterogeneous media that facilitate a transition between them.

For more details, our manuscript can be found here.