Lateral and vertical crustal velocity and density variations in the Southwestern Cuddapah Basin and adjoining Eastern Dharwar Craton

Seismic, gravity and aeromagnetic data are reviewed to understand the complex nature of the structure of the Cuddapah basin. Deep Seismic Sounding analogue data acquired along Kavali-Udipi profile, covering middle and western parts of Cuddapah basin and adjoining granitic gneissic terrain of Eastern Dharwar Craton have been primarily used for this study. We have derived a two-dimensional crustal velocity structure by reprocessing of refraction and wide-angle reflection data acquired along the profile. Derived basement and sub-basement crustal structure has brought out finer structural details. Two layers are present above the upper crust. The first layer has a velocity of 5.2 to 5.4 km/s and the basement has a velocity of 5.95 to 6.00 km/s. The upper crust has a velocity of 6.4 km/s, mid crustal velocity is 6.6 to 6.8 km/s, whereas the lower crustal velocity is 7.4 km/s. Moho-1 is observed at an average depth of 37 km with a derived velocity of 7.8 km/s. A deeper Moho-2 is also observed at a depth of 45 km with a Pn velocity of 8.4 km/s. A low-velocity layer (6.5 km/s) separates the two Moho discontinuities. In addition, the analysis has brought out finer crustal velocity-depth details of the region, including presence of regionally extending upper crustal domal features. The study has also revealed the presence of deep-seated faults near Parnapalle, Tonduru and Malepadu. Gravity modelling of the seismic structure further substantiated the results and brought into focus the good correlation of datasets.