Complicated seismic anisotropy beneath south-central Mongolia and its geodynamic implications

- New SKS splitting observations are presented in Mongolia.
- Anisotropy data argue for asthenospheric flow in the direction of AMP.
- Anisotropy data are sensitive to flow around the Siberian keel.
- Small scale upwelling is generates a set of null measurements observed south of the Hentiy Mountain.

Two years of high-quality broadband seismic data from 69 temporary stations deployed in south-central Mongolia provide an opportunity to study the anisotropy-forming mechanisms in this area. The majority of shear wave splitting observations determined from the analysis of teleseismic SKS phase are characterized by NW-SE trending fast directions with large splitting delay times (greater than 2.0 s at six stations), which is inferred to be generated by active asthenospheric flow. The variation of the fast direction may be associated with deflection of asthenosphere around the deep Siberian cratonic keel at the base of the lithosphere. Several of the NE-SW trending fast directions with relatively small delay times observed in the Gobi Desert are parallel to the strike of the main faults and sutures, which may represent lithospheric deformation. In addition, it is inferred that small-scale hot mantle upwelling is responsible for generating a cluster of null measurements observed on the south of the Hentiy Mountain.