Shear‐wave splitting at central Tien Shan: Evidence for rapid variation of anisotropic patterns

At active collisional belts, the fast polarization axis of shear‐wave splitting is generally aligned parallel to the strike of the belt, which has been proposed to indicate mantle strain that is coherent with crustal deformation. A notable exception is central Tien Shan, where anomalous patterns of splitting have previously been observed. We here analyze shear‐wave splitting of SKS phases across north central Tien Shan using digital data from the Kyrgyzstan Broadband Seismic Network (KNET). We find a pattern of short‐wavelength anisotropic heterogeneity that supports complex mantle flow due to small‐scale convection. The along‐strike variations in mantle structure contrast with the coherent pattern of crustal shortening, and indicate that mantle flow is not directly coupled to crustal deformation in this region.