Site Characterization and Evaluation of Seismic Sources for Amaravati Region

Introduction

Earthquakes are the most powerful and unexpected natural disasters which are unavoidable and unpredictable in nature. According to the Seismic Microzonation Manual (Seismic Microzonation Manual, 2011), twenty-seven Indian cities fall under the vulnerable zone. Most of the recent earthquakes cause severe damage to structural failure and loss of human lives in urban cities all over the world (Ganapathy & Rajawat, 2012). India has encountered some serious earthquakes in past for example, Assam (M_w8.7) in 1897, Kangra-Himachal Pradesh (M_w8.6) in 1905, Bihar-Nepal (M_w8.4) in 1934, Assam-Tibet (M_w8.7) in 1950, Uttarkashi-Uttaranchal (M_w6.6) in 1991, Latur-Maharashtra (M_w6.3) in 1993, Jabalpur-Madhya Pradesh (M_w6.0) in 1997, Chamoli-Uttarakhand (M_w6.8) in 1999, Bhuj-Gujarat (M_w7.6) in 2001 and Muzafarrabad-Kashmir (M_w7.6) in2005 (Mohanty & Walling, 2008; Rajaram, Narender, Satyam, & Kumar, 2010; Rao & Satyam, 2007). As per the Bureau of Indian Standard (BIS), India has been divided into four seismic zones (i.e II, III, IV and V) based on the peak ground acceleration (PGA) and comprehensive intensity scale (CIS) (Mohanty & Walling, 2008). However, the prediction of damage level due to an earthquake is not possible based on the common zone wise fixed PGA values. The impact due to the earthquake on the structures is completely different based on geology, the conflicting seismic response may change location to location and region to region for the same size of the earthquake (Geotechnical/Geophysical Investigations for Seismic Microzonation Studies of Urban Centres in India, 2011; Mohanty & Walling, 2008). The damages due to 1999 Chamoli and 2001 Bhuj (M_w 7.6) earthquakes are very good examples to know how the regional characteristics of the site and geological conditions will influence the level of ground shaking during the earthquake (Anbazhagan & Sitharam, 2008). The Chamoli earthquake focal point situated at more than 250km far away from the Delhi (India), resulting in moderate harm to the structures built on filled-up soil and on delicate alluvium soils. The damage pattern from the Bhuj earthquake (2001) is observed in Ahmedabad which is about 250km away from the epicentral region. According to the 1997 Building Material and Technology Promotions Council (BMTPC), most of the cities in India, having populated one million or more falls under seismic zones III, IV, and V and 59% of Indian landfall under vulnerable to earthquake, in which 26% of landfall in zone III (Vulnerability Atlas of India, 2005).