An empirical relationship between seismic attenuation and velocity anomalies in the upper mantle

We use recent P wave attenuation (Q(alpha)(-1)) and velocity (V-p) tomograp hic models of the Tonga/Fiji region to obtain an empirical relation between attenuation and velocity for the upper mantle. The attenuation and velocit y anomalies show a strong inverse correlation, allowing the determination o f an empirical relationship. The relationship is similar to a predicted rel ation derived from laboratory experiments on peridotite and dunite, assumin g the observed anomalies result from temperature variations. The results he re suggest that the observed anomalies are generally consistent with the ef fect of temperature, and demonstrate that the combination of velocity and a ttenuation data provides powerful constraints on the physical state of uppe r mantle materials. We find that the chosen geotherm and activation energy has a strong effect on the position of the solidus within the seismic data.