Investigating deep mantle evolution by linking geodynamic modelling to seismic data

The alternation between superchrons and periods of rapid field reversals is comparable
to timescales of mantle convection, suggesting that lowermost mantle evolution impacts
the reversal frequency of the Earth’s magnetic field. By controlling the heat flow from
the outer core, the deep mantle temperature distribution can either support or hamper
the convective pattern in the outer core that generates the dipolar field component.

Due to the long timescales, the main means of testing a potential correlation between
reversal frequency rate and CMB heat flow distribution is through tectonically informed
geodynamic modelling. However, even though state-of-the-art mantle circulation models (MCMs) 
typically explain statistical properties of seismological data, they do not consistently 
reproduce the location of present-day mantle features. The main influence
on position is given by the assimilated absolute plate motion model, which is inherently
restricted by the lack of longitudinal constraints as well as the need to separate plate
motion and true polar wander signal in paleo-magnetic data. Geodynamic model predictions 
therefore need to be compared to independent observations.

In this contribution, we investigate predictions of present-day mantle structure that
are based on differences in the absolute plate motion model. We compute synthetic seismic
data by coupling MCM predicted structure with a thermodynamic mineralogical model.
The analysis is predominantly focused on normal mode data, as they capture the longwavelength 
component of structures throughout the entire mantle. In addition, the
global sensitivity of normal modes reduces the drawbacks of uneven data coverage. By
quantifying the fit to seismic data, we evaluate different realisations of mantle structure
that reflect plausible variations in the absolute plate motion history.