One-Dimensional Ground Response Analysis to Arrive at Surface Peak Ground Acceleration—A Case Study of Golaghat District in Assam

Abstract

Ground Response Analysis (GRA) is required to be carried out for predicting ground surface motions and to evaluate dynamic properties of soil during an earthquake excitation. In this study one-dimensional equivalent linear (EL) and nonlinear (NL) GRA was carried out for five boreholes located in Golaghat district of Assam, India. This region falls under highly seismic zone ‘V’. The soil borehole log obtained from standard penetration test (SPT) confirmed alluvial deposits with layers of both coarse and fine-grained soils. The input motions of 2011 Sikkim earthquake of Mw 6.9 recorded at Gangtok station and 1999 Uttarkashi earthquake of Mw 6.8 recorded at Bhatwari station are considered for the analysis. The results are plotted in terms of peak ground acceleration (PGA), maximum stress ratio and maximum strain with depth, and spectral acceleration over range of periods. On comparison of EL and NL methods, the strain profile follows a similar trend along the depth of borehole from both methods. However on comparison of both the methods, NL methods showed maximum shear strain value. It was depicted that the PGA values for a particular site of interest can be determined directly from the peak horizontal acceleration (PHA) even in the absence of dynamic soil properties of the site. Such PGA values can be directly used for earthquake-induced liquefaction analysis and also for building design purposes.