SITE STUDIES IN THE KUMAON REGION

Abstract

The region in and around Kurnaon Himalayas is subject to large seismic risk i.e. Seismic zone V. It is because of constant thrusting that has been taking place between lndo-Australian plate and Eurasian plate, which leads to accumulation of stress which is released in the form of earthquakes. The damages caused by earthquakes are massive in India in general and in Himalayas in particular. The four stations on which I worked (Dharchula, Baluwakote, Jouljibi and Muwani) in Kumaon region are seismically very active because of the reason mentioned above. A seismic ground motion estimate that is accurate across this area is of paraamount importance for development and to be able to mitigate the seismic risk. It is evident from the past experiences that local effects may have a dominant contribution to the intensity of damage and destruction. In the present an effort has been made to find out and identify the dominant frequency/ peak frequency associated with the different sites and soft sediment thickness calculation in the Kumaon region. The site response is obtained in terms of spectral ratio i.e. by taking the ratio o f horizontal and vertical components of motion recorded simultaneously. The next step is the estimation of soft sedimentary thickness. In the present wok, using the H/V spectral ratio method, I have tried to obtain the site effects and their variations due to change in soil condition. The variation in the site amplification and predominant frequency has been obtained. By using the predominant frequency we could design our building in that area so that the building's natural frequency and the predominant frequency of soil do not niatch so to avoid resonance effect. This will minimize the damage in the particular site.