Applications of Two-Dimensional Seismic Tomography for Subsurface Cavity and Dissolution Features Detection Under Doon Valley, NW Himalaya

The presence of natural voids, cavities and palaeochannels under the surface hinders the extension of urbanization particularly in the new upcoming cities in the frontal part of the Himalaya. The Doon valley is characterized by such features. In this context, multichannel analysis of surface waves technique is used as a cost-effective solutions for investigating subsurface cavities, voids, shallow weathered zones and dissolution features in the Doon valley, NW Himalaya. Given the sensitivity of the deduced shear wave velocity to lithology, clast composition, degree of saturation, velocity distribution to a target depth of 40–50 m is a useful guide to demarcate different erosional/ dissolution features, cavities and palaeo-channels. 2D shear wave velocity data sets have been acquired along several profiles in the upcoming region of the Doon valley. Data processing has been carried out at 50 sites and shear wave velocity and profiles were validated taking into account field observations and bore hole data. The subsurface karst features or palaeo-channels are always a matter of concern to engineers before any development starts, because these features could cause subsidence in the region. Anomalies, that include caverns, dissolution features, and erosional channels etched into the Dehradun Fan sediments at shallow depth, have effectively been identified in the 2D shear wave velocity (Vs) field from >50 sites. The subsurface architecture further suggests variation in tectono-climatic condition and shifting of provenance during the fan building processes.