The high-temperature acoustic Grüneisen parameter in the earth's interior

Abstract

The value of the acoustic Grüneisen parameter, γ a, in the earth's interior has been computed using data from recent models obtained by inversion of normal data. In this paper we emphasize the data from the PEM model of the earth because there has been sufficient smoothing of the seismic data so that the derivatives d ln ν s/d ϱ and d ln ν p/d ϱ can be well defined at all depths. The results for the lower mantle show that γ a decreases exponentially from 1.3 to 1.0, and there are several consistent cross-checks of the limiting values. We find γ a is about 1.5 for the inner core and outer core. These results confirm, in broad outline, the results of others who computed γ for the core by entirely different methods. They also confirm a higher value of γ in the inner core. The value of γ a in the lower mantle follows a ρ −1.35 law, which is reminiscent of the expirical law γρ = constant, commonly used in shock-wave analyses.