Estimating core-mantle boundary temperature from seismic shear velocity and attenuation

The temperature at Earth's core-mantle boundary (CMB) is a key parameter to understand the dynamics of our planet's interior. However, it remains poorly known, with current estimate ranging from about 3000 K to 4500 K and more. Here, we introduce a new approach based on joint measurements of seismic shear-wave velocity, V (S), and quality factor, Q (S), in the lowermost mantle. Lateral changes in both V (S) and Q (S) above the CMB provide constraints on lateral temperature anomalies with respect to a reference temperature, T (ref), defined as the average temperature in the layer immediately above the CMB. The request that, at a given location, temperature anomalies inferred independently from V (S) and Q (S) should be equal gives a constraint on T (ref). Correcting T (ref) for radial adiabatic and super-adiabatic increases in temperature gives an estimate of the CMB temperature, T (CMB). This approach further relies on the fact that V (S)-anomalies are affected by the distribution of post-perovskite (pPv) phase. As a result, the inferred T (ref) is linked to the temperature T (pPv) at which the transition from bridgmanite to pPv occurs close to the CMB. A preliminary application to V (S) and Q (S) measured beneath Central America and the Northern Pacific suggest that for T (pPv) = 3500 K, T (CMB) lies in the range 3,470-3880 K with a 95% likelihood. Additional measurements in various regions, together with a better knowledge of T (pPv), are however needed to determine a precise value of T (CMB) with our method.

Automated summary

The translation introduces a new method to estimate the temperature at Earth's core-mantle boundary using seismic measurements, specifically V(S) and Q(S), which provide constraints on the CMB temperature.