Intensity-dependent site amplification factors using non-linear ground response analysis for Greater Srinagar Metropolitan in the deep sedimentary basin of Kashmir

Abstract

This paper includes 1D nonlinear site-response analyses at 154 sites in key geological deposits of the Kashmir Valley, North-Western Himalayas. Responses to a suite of 22 motions of varying intensity (peak accelerations ∼0.01 g–0.86 g) from global and regional records were studied, using the entire depth to geological bedrock for the sedimentary deposits. Acceleration response spectra and amplification factors (AFs) were proposed for different geomorphological units of the region. Rock sites showed AF ≈ 1 for long periods (>1 s), and 1–1.5 for shorter periods (<1 s) at all intensities. Deep sedimentary sites had AFs as large as 2.76 for low-intensity motions, and as low as 0.11 for high-intensity motions. Short-period factor, F_a, was lower (∼0.29–2.32) compared to the long-period factor, F_v, for the deep deposits. This indicates that seismic codes underestimate response at long periods in deep soil deposits, which could cause undesirable seismic performance of tall buildings.