The 2.5D crustal density structure is modelled using complete Bouguer anomaly along two W-E profiles across the Marwar block, Aravalli-Delhi Fold Belt (ADFB), and the Bundelkhand craton, constituting the north-western edge of the Indian Shield. The rock density closely mimics the litho-tectonic units that preserve the Archean-Proterozoic evolutionary history. The Bouguer anomaly along the profiles, corresponds to significant variation in crustal structure, with Moho depth varying from 34 to 40 km under the Marwar block, similar to 45 km under high-relief ADFB and <42 km under the Bundelkhand craton. A high density (2.78 g/cm(3)) 6-8 km thick sill in the upper crust and a 10-12 km thick high-density (3.05 g/cm(3)) body as the mantle underplating at the Moho, represent the source conduit of the Neoproterozoic Malani Igneous Suite in the Marwar block. The significant lithological variation within the 8-10 km thick upper crust with a 12-13 km thick elongated high-density (3.05 g/cm(3)) basaltic body with a diffused Moho signature, possibly representing the mantle underplating due to orogenic root delamination under the ADFB. The lateral variation in the crustal structure across the craton suggests the orogenic reworking during the early-mid Proterozoic and mantle upwelling in an extensional regime during the Neoproterozoic in the ADFB and Marwar lock.
This study employs seismic techniques for the site characterization of the Korba region in Chhattisgarh, India. Seismic activity has been reported in this region lately, classifying this region in seismic zone III, according to the Building Materials and Technology Promotion Council (BMTPC) assessment (2006). We gather data from 30 different locations in the Korba region, using the Tromino instrument. We estimate the fundamental frequency, construct shear wave velocity for subsurface classification of the Korba region, and develop Horizontal-to-Vertical Spectral Ratio (HVSR) curves for ambient noise data in accordance with the National Earthquake Hazards Reduction Programme (NEHRP) criteria. We calculated the liquefaction vulnerability index (Kg), amplification value, and peak resonant frequencies from the HVSR curve. Amplification factors range from 1.18 to 10.02, while the peak resonant frequencies span from 1.146 to 15.062 Hz. Vs30 for the region varies between 140.06 and 646.90 m/s. These findings indicate presence of soft soil in the western portion of the region, which is situated along the Hasdeo River's bank. In majority of the places, we discovered that the Kg value was less than 10, indicating low liquefaction vulnerability in the examined area.
