TEMPERATURE-FLUCTUATION AND THERMODYNAMIC PROPERTIES IN EARTHS LOWER MANTLE - AN APPLICATION OF THE COMPLETE TRAVEL-TIME EQUATION OF STATE

The complete travel time equation of state (CT-EOS) enables us to obta in all the thermodynamic parameters from travel time or velocity measu rements of elastic waves at simultaneously high pressure and temperatu re. Here we formulate the adiabatic CT-EOS and apply it to the lateral heterogeneity of seismic wave velocity in the lower mantle. We obtain ed internally consistent results for temperature, thermal expansivity and the Gruneisen constant in the low mantle; at the depth (2741 km) j ust above D'' layer, the most likely results are similar to 2500 K for temperature, similar to 1.0X10(-5) K-1 for thermal expansivity and si milar to 1.0 for the Gruneisen constant. We also discuss the geophysic al implication of the small thermal expansivity suggested in the deep lower mantle.