Earthquake seismic site response analysis by comparison between equivalent linear and nonlinear methods, a case study at Kohat and Muzaffarabad

Abstract

The effects of natural disasters such as earthquakes on our environment lead to different earthquake analysis. Seismic site response analysis is one of these analyses, which can be done using different methods. The seismic response analysis carried out in this research was based on Equivalent linear and Nonlinear method. Two seismically active regions which are part of Kohat Platue (Shakardarra) and Hazara Kashmir Syntaxes (Muzaffarabad) were selected. The sites were tested for vertical component input ground motions of magnitude 7.0ML (PGA= 0.07g) and 4.9mb (PGA= 0.018g). The soil profiles for both sites were prepared on the average results of five geotechnical (SPT) upholes data at Muzaffarabad (MUZ) site and twenty seismic upholes data at Shakardarra (SHD). The soil samples collected at MUZ site were sandy gravel, sand and clay and at SHD sandy gravel, sand, clayey sand and clay, for which were tested for damping ratio of 5% using site response analysis programs (NERA and EERA). The stress-strain models, strain energy models, response models (amplification models, Fourier response models and spectral response models) were constructed for each type of soil sample on the basis of input motions data using NERA and EERA, which were then compared. According to comparison, the soils at sites were under great stresses and these exhibited negligible amount of strains, the PGA values calculated were interpreted as incompatible for intermediate to high man-made buildings.