On DLA's eta
On DLA's eta (in The interdisciplinary Earth; a volume in honor of Don L. Anderson, Gillian R. Foulger (editor), Michele Lustrino (editor) and Scott D. King (editor))
Special Paper - Geological Society of America (August 2015) 514: 33-38
In his pioneering 1961 paper on seismic anisotropy in a layered earth, Don L. Anderson (hereafter referred to as DLA) introduced a parameter often referred to in global seismology as eta without providing any reasoning. This note hopes to clarify the significance of eta in the context of the dependence of body wave velocities in a transversely isotropic system on the angle of incidence, and also its relation with the other well-known anisotropic parameters introduced by Leon Thomsen in 1986.