Seismic anisotropy and mantle deformation in NW Iran inferred from splitting measurements of SK(K)S and direct S phases

SUMMARY We present the results of a shear wave splitting analysis performed on teleseismic SK(K)S and direct S recordings 68 temporary broad-band stations to investigate mantle deformation northern side Arabia–Eurasia collision zone in NW Iran. used Reference Station Technique overcome potential contamination from source-side anisotropy signals. This method enabled us expand our measurement database beyond usual phases. The average delay time over entire region was found be 1.14 ± 0.42 s for 1.36 0.26 wave. In most parts study area, fast polarization directions both phases are consistent show uniform NE–SW direction with an 36° 37° wave-derived results, respectively. is close agreement absolute plate motion vector Iran (N39°E). associated neither surface geological trends, nor geodetic strain fields. propose that observed mainly controlled by LPO fabric developed due shearing asthenospheric layer response lithosphere relative deeper mantle. Only narrow near tectonic boundaries central Alborz, NW–SE oriented tend align major structures. Fast obtained indicate significantly smoother variations same regions mostly continue aligned direction. attribute these differences change structure boundary zone. western margins possess strong deformational as evidenced active strike-slip zones there. Considering depth extent this expands relatively mantle, it can locally influence waves, other hand, have larger footprint therefore region, phases, influenced more strongly their angles incidence, which station parameters.