Heterogeneity and anisotropy of seismic attenuation in the inner core

Abstract

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 150° to 170°. 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 50°E to 120°W) or the western hemisphere. In the eastern hemisphere the parameter t ★ 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 ★ is weakly dependent on the distance, and varies between approximately 0.7 s and 0.1 s for the angles between 0° and 90°, 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.