Heterogeneity and anisotropy of seismic attenuation in the inner core

We evaluate seismic attenuation in the inner core from the spectral ratio between the seismic phase PKP(DF) and either PKP( AB) or PKP( BC) at the epicentral distances from 150degrees to 170degrees. The global data set is divided into two groups according to the position of the turning point of PKP(DF) either in the eastern (from 50degreesE to 120degreesW) or the western hemisphere. In the eastern hemisphere the parameter t(star) shows strong dependence on the epicentral distance and no dependence on the angle between the Earth's spin axis and PKP(DF) ray at the turning point. In the western hemisphere t(star) is weakly dependent on the distance, and varies between approximately 0.7 s and 0.1 s for the angles between 0degrees and 90degrees, respectively. Our results allow us to reconcile seemingly incompatible results of many previous studies. The anisotropy of attenuation is correlated with the anisotropy of P velocity.