Geotechnical and Structural Damage in Tamil Nadu, India, from the December 2004 Indian Ocean Tsunami B. K. Maheshwari, a… M.EERI, M. L. Sharma, a… and J. P. Narayan a… A reconnaissance team surveyed the geotechnical and structural engineering aspects of tsunami damage on the coast of Tamil Nadu in India. The area surveyed was from Chennai on the east coast to Thiruvananthapuram on the west coast. There was practically no major evidence of damage from direct ground shaking, although damage from the tsunami was extensive. The geotechnical engineering damage observed was mostly due to erosion of soil, settlement of soil, damage to port and harbor facilities, and damage to lifelines. The structural engineering damage involved damage to compound walls, collapse of rural houses, failure of columns, and toppling of roofs; some of the damage occurred because reinforcement details were lacking. Analyses of damage and its causes were performed, and the level of damage correlated well with the tsunami runup for the localities visited. DOI: 10.1193/1.2206148 INTRODUCTION The Great Sumatra earthquake of 26 December 2004 with moment magnitude M w = 9.3 Stein and Okal 2005 caused a widespread tsunami. The authors visited the coastal region of Tamil Nadu and Pondicherry in south India Figure 1 during 6–14 January 2005 for a reconnaissance survey. The main objectives of the team were to ob- serve the effects of the 26 December 2004 tsunami on the built environment in terms of geotechnical and structural damage, to measure the inundation and runup of the tsunami waves and their variation, and to determine the arrival time of the tsunami Narayan et al. 2005a. There are 13 districts of Tamil Nadu whose boundaries include part of the seacoast. The authors visited 10 districts, including Pondicherry. Of 45 towns and communities that were visited, 37 sites were directly affected by the tsunami. Nagapattinam, Kanaya- kumari, and Cuddalore were the most severely affected districts. The highest wave re- ported was 12 m in Nagapattinam. Among the visited communities, the towns of Keela- manakudy and Meelamankudy, in the Kanayakumari district, suffered the most structural damage. This paper presents in detail the geotechnical and structural aspects of the damage observed, analyzes the correlation between damage and the level of runup, and suggests preventive measures. a Department of Earthquake Engineering, Indian Institute ofTechnology, Roorkee, U.A. 247 667, India S475 Earthquake Spectra, Volume 22, No. S3, pages S475–S493, June 2006; © 2006, Earthquake Engineering Research Institute