Anisotropy in the crust and upper mantle at the Great Wall seismic station in Antarctica

Using the earthquake events from February 2008 to March 2010 recorded by the Great Wall seismic station in Antarctica, which is from the 24th and 25th Antarctic scientific expeditions, this paper studies the shear wave splitting. By choosing the local earthquakes and using Sg waveforms to study the shear wave splitting, the polarization direction of the fast wave are northeast and nearly north-south. The delay time of the slow wave is in the range of 1.45—5.17 ms/km with the average value being 3.54 ms/km. By choosing the teleseismic events and using SKS waveforms to calculate the parameters of shear wave splitting, the polarization direction of the fast wave is northeast, and the average delay time of the slow wave is 1.60 s. The results of shear wave splitting shows that the anisotropy in the crust and upper mantle is obvious. And the polarization direction of fast wave in the crust is parallel to that in the upper mantle, which indicates the deformation in the crust and upper mantle is identical. In addition, the anisotropic directions of fast wave polarizations in the crust and mantle are parallel to the direction of ocean trench around the Great Wall seismic station and to the direction of the absolute plate motions, which further suggests that the absolute plate motions are the primary cause of the upper mantle anisotropy.