Temperature Coefficient of Sound Velocity of Perovskite-Enstatite and Lateral Thermal Heterogeneity in Earth’s Lower Mantle

Using the differences of sound velocity and temperature on the Hugoniot and isoentropic state, the temperature coefficients of sound velocity of perovskite-enstatite under high pressure were obtained. For compressional, shear and bulk wave velocities, their temperature coefficients decrease from 0.386, 0.251, 0.255m/(s.K) at 40 GPa to 0.197, 0.131, 0.162m/(s.K) at 140 GPa, respectively. Extrapolating these to zero pressure results in (∂K/∂T)₀ = -0.0279 GPa.K^-1, which is consistent very well with the value got by hydrostatic pressure experiment. On the basis of our data, we conclude that the compressional wave velocity anomaly of 0.1-0.2% in the deep lower mantle and 2% in the D" region would imply lateral thermal heterogeneity with amplitude of 53-106K and 1066K in these regions, respectively.