P5: Linking of seismic tomography models and geodynamic Earth models

Supervisors

Prof. Heiner Igel, Prof. Hans-Peter Bunge

Advisors (int.)

Dr. Bernhard Schuberth (LMU)

Advisors (ext.)

Prof. Andreas Fichtner (ETHZ), Dr. habil. Christophe Zaroli (Univ. Strasbourg)

Description

This project links mantle state estimates derived from seismic tomography to flow inducing geodynamic heterogeneity structure. We will investigate the effects of mantle mineralogy and limited tomographic resolution on the relation between thermal and seismic mantle structure in geodynamic models. Important questions involve tomographic filtering effects; that is, seismic tomography provides us only with a low-pass version of the true Earth structure. Additional complexity arises from the fact that tomographic models of Earth’s mantle represent 3-D variations in seismic velocity, while geodynamic models require estimates of its present-day thermodynamic state in terms of buoyancy variations (i.e., density). Mineralogical models can be used to convert the seismic velocity information to density (and vice versa) if effects such as anelasticity and phase transitions are considered. New opportunities arise, because the focus in seismic tomography is shifting from merely increasing the resolution towards additionally providing formal means to quantify image resolution and model uncertainty. Probabilistic inversions based on Bayesian inference on the one hand and the SOLA Backus–Gilbert tomographic scheme on the other hand are promising The latter does not only provide information on resolution and model uncertainty, but can also be applied to large inverse problems on the global scale.

Main objectives

  • Exploring the effects of tomographic filtering on estimates of the thermodynamic state of the mantle
  • Investigating ways how to treat the inevitable difference in characteristic length scales between global whole mantle seismic tomography and geodynamic forward models
  • Investigating anelastic effects on the mineralogical mapping and on the seismic signature of mantle convection models
  • Exploring the effects of uncertainties in seismic tomography and mantle mineralogy on geodynamic inverse simulations
  • Provision of an representative ensemble of thermodynamic state estimates of the mantle for the geodynamic inverse simulations

RTG coupling

Input:

  • Mineralogy (conversion between material parameters, i.e. seismic velocities, density, temperature) (external)
  • Forward uncertainty estimates for the material parameters from P9.

Output:

  • Geodynamic mantle heterogeneity structure for P2, P6, P8 and P9 to link togeodynamic retrodictions and their uncertainty.
  • Visualization of geodynamic heterogeneity (P10).