Importance of anelasticity in the interpretation of seismic tomography

TLDR

Seismic wave velocity temperature dependence arises from both anharmonicity and anelasticity. Anelasticity significantly amplifies mantle temperature effects, reducing inferred temperature anomalies and increasing shear‑wave velocity contrasts compared to anharmonicity alone.

Abstract

Temperature dependence of seismic wave velocities comes both from anharmonicity and anelasticity. The contribution from anelasticity is shown to be important in the Earth's mantle particularly for shear waves. In the low Q (Qµ∼100) regions in the upper mantle, the correction due to anelasticity will roughly double the temperature derivatives due to anharmonicity alone. The correction for anelasticity will also be important in the deep mantle where Q is larger, if temperature derivatives due to anharmonicity will decrease significantly with pressure. These results imply that the temperature anomalies associated with low velocity anomalies in the mantle will be significantly smaller than previously considered on the basis of anharmonic effect alone and that the amplitude of velocity anomalies will be significantly larger for shear waves than for compressional waves.