Mantle Deformation Patterns Beneath the Central India Tectonic Zone: Evidence from SK(K)S Splitting Measurements in the Satpura Gondwana Basin and Adjacent Areas

Abstract. This study presents shear wave splitting (SWS) estimates for core-refracted SK(K)S phases utilizing data from nine seismic stations in the Central Indian Tectonic Zone (CITZ) that were temporarily operational between July 2023 and July 2025. The CITZ was formed during the Mesoproterozoic orogeny in central India, resulting from the collision of the northern Bundelkhand Craton with a jumble of South Indian Cratons. We used rotation-correlation and transverse energy minimization methodologies to ascertain the SWS parameters, the fast polarization directions (FPDs) and splitting delay times (δt). A total of 129 high-quality SWS measurements were obtained from 87 earthquakes (M>5.5) at epicentral distances between 84°–145° for SKS phases and 84°–180° for SKKS phases. The mean δts at each seismic station ranges from 0.7 to 1.4 seconds, demonstrating the upper mantle heterogeneity in the study region. Most stations show NE-SW FPDs, aligning with the Absolute Plate Motion (APM) of the Indian plate. The difference between mean FPD and APM direction at some stations suggests the presence of 10 fossilized anisotropic fabrics resulting from prior subduction events during the Mesoproterozoic Era. Seismic stations near the Deccan Volcanic Province and mantle dyke zones have lower δt (<1 second) values, indicating significant magmatism during the Cretaceous period. Our findings suggest that the mantle flow beneath the CITZ is affected by both the present APM direction of the Indian plate and lithospheric frozen anisotropy resulting from prior Mesoproterozoic orogeny and Cretaceous mantle plume activity.