Quantifying seismic vulnerability, dynamical shear strain and liquefaction of the Quaternary deposits in the Doon valley near the Main Boundary Thrust in the Northwest Himalaya, India

The spot resonant frequencies increases from 1 Hz to more than 6 Hz from the HFT region to the MBT, while the amplification factor decreases from 14 to 1. In general, the valley soft soil is susceptible for liquefaction because the estimated dynamical shear strain is 15-25 millistrains under medium (2.2 m/s2, 225 years) and long (4.6 m/s2, 2500 years) term strong motion conditions, which is much higher than the soil plasticity limit of ten millistrains that lead to liquefaction. Dynamical shear strain distribution with depth at eight boreholes in the valley indicate ∼20 m is the liquefaction potential depth, where the pore pressure induced peak shear strain exceeds the threshold shear strain of 0.01% during the passage of seismic waves. Isolated locations in the valley like that at Dharmawala (H1), where all site parameters are very high, and would be hazardously vulnerable to liquefaction. However near the MBT the liquefaction possibility of soft soil is less, but would experience ground deformation of more than 50 cm.