Complex upper mantle deformation beneath the Dharwar craton inferred from high density splitting measurements: Distinct lateral variation from west to east

摘要: Abstract Upper mantle anisotropy investigated using 172 core-refracted (SKS, SKKS) seismic phases along a ~660 km long profile at 10 to 20 km intervals from the west east coast of South India reveals significant lateral variations in its magnitude and direction. This profile, with 38 broadband stations, covers mid-Archean Western Dharwar craton (WDC), late-Archean Eastern Craton (EDC), Proterozoic Cuddapah Basin (CB) passive continental margins coast. The observed fast polarization directions (FPDs) show variability: NW50o NW5o beneath WDC, NW40o NE30o EDC N5o N85o CB further east. delay time varies between 0.4 2.0 s an average 1 s. However, we are unable fit two layers model for region due sparse azimuth coverage. Beneath direction axis follows trends shear zones faults, suggesting “frozen-in” lithosphere, possibly established during lithospheric evolution mid-late Archean. In EDC, does not only follow plate motion but it deviates, manifesting late Archean deformation may still be present as fossil anisotropy. splitting trend Ghat (EG) strike rift direction, indicating is influenced by combination “frozen” rifting eastern margin Indian active asthenospheric flow.