Thick and anisotropic D″ layer beneath Antarctic Ocean

Waveform modeling and travel times analyses of S, ScS and SKS phases recorded at the broad‐band permanent station SYO in the Antarctic are used to determine the shear wave velocity structure and transverse isotropy in the D″ layer beneath the Antarctic Ocean. The SH wave structure has a discontinuity with the velocity increase of 2.0% at 2550 km. The SV structure is similar to PREM model. The magnitude of the anisotropy is highest at the top of D″ layer and lowest at the core‐mantle boundary. The D″ layer beneath the Antarctic Ocean is significantly thicker than those beneath Alaska and the Caribbean Sea. We attribute this anisotropic D″ layer to paleo‐slab materials. The subduction in and around the Antarctic Ocean has started ∼180 Ma and is the one of the oldest in the world. It has provided a large amount of the slab materials in the lowermost mantle.