SEISMIC GROUND RESPONSE ANALYSIS ON DIFFERENT SITES FOR SITE AMPLIFICATION

Abstract

The north eastern part of India is one among the most seismically active region in the world. It lies in the zone 5 of the seismic zonation map of India. The region has experienced abundant earthquakes covering 18 large earthquakes of magnitude greater than 7 during the last century. The reason for the high seismicity in this part of India is that there is a collision between Indian plate and Eurasian plate in the north and subduction along the Indo-Myanmar range in the east. Also, maximum seismicity is observed where subduction is taking place. Response of seismic ground motion across the region is very much essential for minimising the seismic risk and building structures. Past experience suggests that effects of local geology and soil condition plays a very important role in the amplification of earthquake. Due to this, there is large scale destruction of properties and loss of human life. Current work deals with the amplification and peak frequencies associated with different sites. Site response analysis is done using Nakamura’s method where spectral ratio is obtained by dividing the horizontal component of acceleration record by the vertical component. Average of horizontal component is taken so as to obtain reliable results. Horizontal to vertical ratio is then plotted against frequency content to get site amplification. Site amplification obtained for different sites is in accordance with the geology of the sites.