The complete travel time equation of state (CT-EOS) enables us to obtain all the thermodynamic parameters from travel time or velocity measurements of elastic waves at simultaneously high pressure and temperature. Here we formulate the adiabatic CT-EOS and apply it to the lateral heterogeneity of seismic wave velocity in the lower mantle. We obtained internally consistent results for temperature, thermal expansivity and the Gruneisen constant in the lower mantle; at the depth (2741 km) just above the D″ layer, the most likely results are ∼ 2500 K for temperature, ∼ 1.0 × 10-5 K-1 for thermal expansivity and ∼ 1.0 for the Gruneisen constant. We also discuss the geophysical implication of the small thermal expansivity suggested in the deep lower mantle.
ASJC Scopus subject areas
- Geochemistry and Petrology
- Earth and Planetary Sciences (miscellaneous)
- Space and Planetary Science