Prediction of Future Surface PGA in the States of Indo-Gangetic Basin Considering Site Specific Studies

Indo-Gangetic Basin (IGB) is the major geographical region of India extending from Punjab to Bihar including Uttar Pradesh (UP) and Haryana. In this region, major earthquake damages have been reported in the past. Several attempts have been made for different site response studies and estimation of earthquake risk in the region. However, most of them consider only shallow soil information < 50 m and available ground motions. Present study attempts to analyze the spatial variation of peak ground acceleration (PGA) at surface for possible future scenario earthquakes in and around IGB. The earthquakes were identified based on past seismic gaps and studies whose magnitudes ranged from Mw 7.5 to Mw 9.0. The earthquakes were simulated for 270 sites with available shear wave velocity data throughout the IGB. Using proper input parameters of soil column profiles, shear wave velocity, depth of input motion, suitable shear modulus reduction and damping curves; the detailed analyses were carried out using DEEPSOIL. This paper arrives at spatial variation of PGA at surface due to individual earthquakes. The response (bedrock as well as surface PGA) of different states toward each earthquake has been tabulated. Sites in Bihar reflect average and maximum surface PGA 0.15 g and 0.68 g, Uttar Pradesh 0.10 g and 1.18 g, Punjab and Haryana 0.12 g and 0.62 g respectively. These values are indicative of the sensitiveness toward earthquake damages. Maps representing surface PGA for each scenario earthquake were plotted giving detailed information about the surface seismic hazard of the area associated with each earthquake.