The twin events of the earthquake and tsunami not only stress the importance of an integrated warning system for the Indian Ocean rim countries but also the need for new disaster management plans to mitigate such hazards. As far as the Indian coastal regions are concerned, detailed geophysical surveys on the coastal morphology, structure and coastal seismicity are very essential in order to understand the relationship between tsunami run-up heights, inundation extent and the shelf/slope morphology. Studies on coastal structure and seismicity are useful in estimating the seismic hazard risk of the coastal region as well as in understanding the influence of tectonics on the tsunami initiation and surge. In this chapter, a detailed analysis on the morphology, structure and seismicity of the Cauvery offshore basin, which includes the tsunami-affected Nagapattinam-Cuddalore shelf of Tamil Nadu margin is presented.