SPECIFIC SITE RESPONSE ANALYSIS ON THE DIFFERENT EARTHQUAKE MOTION IN KATHMANDU VALLEY

Abstract

Seismicity is a critical concern in Nepal, particularly in the Kathmandu Valley, a region characterized by complex geological and geotechnical conditions. A Study presents a comprehensive site-specific response analysis of the Kathmandu Valley, employing the DEEPSOIL software for non-linear one-dimensional analysis to provide a thorough understanding of the valley’s seismic behaviour, with a focus on the impact of five distinct earthquake motions, including the Gorkha Earthquake, Loma Gilroy Earthquake, Aftershocks of Gorkha Earthquake, Chi-Chi Earthquake, and Kobe Earthquake. The study offers a thorough summary of the amplification factors (AF) and earthquake events for seismic hazard assessments and engineering designs on how the ground motion is amplified or attenuated during seismic events. In comparison to other input motions, the result demonstrates a larger value of amplification factor for the Gorkha Earthquake motion and its aftershocks motion. The Kobe earthquake motion represents the remarkable exception, where amplification considerably decreased. Balaju stands out as the region with the highest ground motion amplification, which can be related to the existence of layers of gray loose micaceous silty fine sand in its subsurface geology. Additionally, this study compares its findings of the site-specific spectral acceleration with the recommended design spectra of IS 1893:2016 and NBC 205:2020 for a 5% damping ratio. Specifically considering the soft soil and very soft soil conditions as per IS 1893:2016 and NBC 205:2020, respectively, this analysis offers a critical evaluation of how the predicted spectral accelerations correspond with designated seismic design principles.