Deep seismic image enhancement with the common reflection surface (CRS) stack method: evidence from the Aravalli–Delhi fold belt of northwestern India

Abstract

Imaging of deep crustal features from narrow-angle deep seismic reflection data, especially from fold belt region, has been a challenging task. The common reflection surface (CRS) stack is an alternative seismic imaging technique for multicoverage reflection data. It is an automatic stacking process, which does not require explicit knowledge of stacking velocity. This CRS stack is especially useful when the data quality is poor and foldage is low. In this paper, we demonstrate an application of the CRS stack to a deep seismic reflection data set acquired across the Aravalli–Delhi fold belt of the northwestern India, which provides a seismic stack section with much improved signal-to-noise ratio. Comparing the conventional common mid-point (CMP) Stack with the CRS stack, we find that the Moho and other crustal reflections have been resolved clearly and the continuity of the reflectors has also been enhanced with the CRS stack method. The major findings from our CRS processing include clear image of the Moho discontinuity below the Marwar Basin and Sandmata Complex, and prominent upper and mid-crustal reflections. Our study for the first time images an extension of crustal-scale Jahazpur thrust below the Sandmata Complex, which becomes listric at the Moho. Some of the crustal features derived in this study were not identified in the earlier investigations using the CMP stack. Our study clearly demonstrates that the CRS stacking method is more appropriate for imaging the crustal and subcrustal structures of the thrust fold belt region than the conventional CMP method, where limited velocity information is available. Crustal thickness across the Proterozoic orogenic Aravalli–Delhi fold belt varies between 38 and 50 km. Global correlation of the seismic results suggests no relation between crustal thickness and age of the crustal block, but it depends on the thermorheological and tectonic history of the region. Palaeosignatures of the Proterozoic subduction and collision processes are still preserved in major portion of the crust in this study area as well as in several parts of the world.