Abstract:
The characterisation of near-surface geological units using shear-wave velocity (Vs) profiles is essential for proper application of ground motion prediction models, and for seismic hazard and risk assessment. A hybrid approach is proposed in the presented paper for the estimation of Vs profile of near-surface geological units. The datasets of standard penetration test (SPT) and one-dimensional multi-channel analysis of surface waves (MASW) surveys have been employed for this purpose. A town and peripheral areas in Karachi, Pakistan were selected for this study. The data analysis indicated presence of mostly deep sandstone layers in the study areas along with other types of deposits. The maximum Vs to a depth of 30 m (98 ft) (Vs30) was found to be 1372 m/sec (4500 ft/sec) which confirms presence of soft rocks. The maps of Vs30 for the study area for pre- and post-disaster mitigation have also been proposed in the presented paper.