Amplification from Isoseismal Map and Site Response Analysis Anbazhagan P Lecturer, Department of Civil Engineering, Indian Institute of Science, Bangalore – 560012, Email: anbazhagan@civil.iisc.ernet.in Abhishek Kumar Research Scholar, Department of Civil Engineering, Indian Institute of Science, Bangalore – 560012, Email: abhishek@civil.iisc.ernet.in Sitharam T G Professor, Department of Civil Engineering, Indian Institute of Science, Bangalore – 560012, Email:sitharam@civil.iisc.ernet.in ABSTRACT: Devastating earthquakes have caused large causalities in the early 20 th century in Himalayan region. Owing to the increase in population and with the increase in the infrastructure, compared to the past the damages will be catastrophic is case of any future event. Many researchers have highlighted the possible existence of seismic gap along the Himalayan region both in terms of time and location. Understanding of site effects and amplification become mandatory in this region. Site amplification depends on the dynamic properties of soil, thickness above rock/ hard layer and input ground motion. Limited attempt has been made in India to measure and understand site effects in deep basic due to paucity of recorded ground motion data at rock and ground. Hence in this paper an attempt has been made to estimate amplification from past event isoseismal map and compared with the surface PGA (Peak Ground Acceleration) obtained from site response analysis for selected sites. INTRODUCTION Loss of lives, devastation and economy loss due to the occurrence of the earthquake events worldwide are frequently reported and necessitates the understanding of earthquake and related hazards to reduce these losses. Studies of such consequences are important in urban area where unpredictable population growth and development in infrastructures and other area of important facilities are undergoing. Himalayas are one of the most earthquake prone regions in the world rising due to the collision of Indian and Eurasian plate. The rate of collision between plates is about 5 mm to 21 mm per year (Khattri, 1987; Bilham et al., 2001). In the light of built-up strains and probable seismic gaps in this region, it is expected large earthquake in near future (Khattri, 1999; and Bilham and Gaur, 2000, Anbazhagan et al., 2010). Major earthquake damages are reported worldwide due to earthquake geotechnical hazard of site effects, liquefaction and landslides. Many classical examples are available of damage due to thick soil deposits world wide. Two well known examples of site effects in India are building damages in Delhi due to Chamoli earthquake and severe collapse of structures in Ahmedabad and other places due to Bhuj earthquake in 2001. Both the regions are far from the earthquake epicenter but still suffered damages due to the site effects a caused by thick soil deposits. Instrumentation and study of site effects due to thick soil deposit are well understood in developed countries, which helped them to reduce seismic damages even for large earthquake like Chile 2010. But limited attempt has been made to understand the site Third Indian Young Geotechnical Engineers Conference (3IYGEC) 25 - 26 March 2011, Indian Geotechnical Society, New Delhi