Global thermochemical inversion of seismic waveforms, gravity satellite data, and topography

Conventional methods of seismic tomography, topography, gravity and electromagnetic data analysis and geodynamic modelling constrain distributions of seismic velocity, density, electrical conductivity, and viscosity at depth, all depending on temperature and composition of Earth's rocks. However, modelling and interpretation of multiple data provide a multifaceted image of the true thermochemical structure of the Earth that needs to be consistently integrated. A simple combination of gravity, electromagnetic, geodynamics, petrological and seismic models alone is insufficient due to the non-uniqueness and different sensitivities of these models, and the internal consistency relationships that must connect all the intermediate parameters describing the Earth. In fact, global Earth models based on different observables often lead to rather different images of the Earth. A breakthrough in global and consistent imaging of the fine-scale thermochemical hydrous and rheological structure of the Earth's lithosphere and underlying mantle is needed. Thermodynamic and petrological links between seismic velocities, density, electrical conductivity, viscosity, melt, water, temperature, pressure and composition within the Earth can now be modelled accurately using new methods of computational petrology and data from laboratory experiments. The growth of very large terrestrial and satellite geophysical data over the last few years, together with the advancement of petrological and geophysical modelling techniques, now present an opportunity for global, thermochemical and deformation 3D imaging of the lithosphere and underlying upper mantle with unprecedented resolution. Here we present a method for self-consistent joint inversion of multiple data sets, including seismic, satellite gravity and surface topography data, applied to obtain a detailed and robust global thermochemical image of the lithosphere and underlying upper mantle. This project combines state-of-the-art seismic waveform tomography, newly available global gravity satellite data (geoid and gravity anomalies and new gradiometric measurements) and surface elevation within a self-consistent thermodynamic framework where seismic velocities and density are dependent on temperature, pressure and composition.