Near surface Geophysical characterization of Baner hill region, Pune, India

Abstract

This study aimed to investigate the near-surface at the Baner hill region, Pune, India. Seismic refraction and Multi-Channel Analysis of Surface Waves (MASW) have been utilized for near-surface imaging. The data was acquired using a 24-channel engineering seismograph along a walking track on the hill at around 665 m above MSL. The topography along the profile is predominantly flat, making a reliable MASW data analysis. The data is processed and inverted to obtain the P- and S-wave velocity image of the subsurface. Both the P- and S-wave models demonstrate an excellent correlation which gives us confidence in using the obtained model to interpret in terms of variation of elastic properties of the subsurface and distinguish various geological units. We identify three geological units, namely weathering zone at the top, followed by two distinct lave flows within the top 55 m of the subsurface. Comparing the obtained velocity to literature reported velocities in Deccan Volcanic Province indicates that the flow below the weathered zone is vesicular basalt while the second flow is massive basalt. It is also observed that the top of the massive basalt controls the weathering in the region as the weathering front mimic the top of the massive basalt. We have also estimated the Poisson's ratio and normalized Young's modulus of all three units to characterize these units further. Such analysis could significantly help infrastructure development projects, groundwater studies, etc., in a volcanic province.