A deterministic seismic hazard analysis for the major cultural heritage sites of Tamil Nadu, India

As stated in several studies Tamil Nadu is the eleventh largest state in India by area and the seventh most populous state and also it is the fifth largest contributor to India′s GDP and the most urbanised state in India. The region has been the home of the Tamil civilization since at least 1500 BC, as attested by numerous archeological sites in and around Adichanallur. Tamil Nadu is home to many natural resources, grand hindu temples of Dravidian architecture, hill stations, beach resorts, multireligious pilgrimage sites and eight UNESCO World Heritage Sites. Bureau of Indian Standard (2001) categorized Tamil Nadu under Seismic Zones II and III, representing an area of 73% and 27% respectively. It should also to be noted that the major historical and Heritage sites like Mahabalipuram, Kamakshi Amman Temple in Kanchipuram, Kapaleshwarar temple in Chennai are fall in Zone III of Moderate Hazard (Figure 1). In this connection these heritage sites has to be evaluated for Seismic Risk. As a first step the potential seismic hazard for these sites evaluated based on deterministic approach.

A catalog of historical/instrumental earthquakes/earth tremors in the state is prepared and used in this paper. The seismic sources have been identified using remote sensing images with limited ground truth verification. Six near potential seismic sources in the region delineated as area sources for seismic hazard assessment based on geological, seismological and geophysical information. Shortest distance from the each seismic source to the major cities of Tamil Nadu measured and the Peak Ground Acceleration (PGA) at bed rock level is calculated for the six sources with their maximum credible earthquake events using available attenuation relationship formula applicable to Peninsular India. The maximum magnitude associated with these potential seismic sources is in the range of 6.0 to 5.0 in Richter scale and the estimated of Peak Ground Acceleration at the source is 0.212 to 0.078g. The PGA values are estimated from the closest potential source for major Cultural heritage sites of Tamil Nadu viz., Kapaleshwarar Temple, Mahabalipuram Group of Temples, Kamakshi Amman Temple in Kanchipuram, Chola group of Temples in Thanjavore and the Mountain Railways of Nilgris calculated. The result of the present study reveals that the seismic hazard in northeastern and western part of the state is closely matching with the Seismic Zonation map published by the BIS. The Mountain Railways is threat to 0.16g by the Nilgiris fault, Chola temple is close to the basement fault which can generate 0.145g to the temples and Kapaleswarar temple sites shows PGA value of 0.107g. However the other sites show lesser PGA value. The sites closer to Chennai city are liable to seismic site amplification these sites have to be studies in detail in future.