Tsunamis are giant waves that form when large sections of seafloor undergo abrupt and violent vertical movement due to fault rupture, landslides, or volcanic activity. A discussion on their formation, propagation in deep and coastal oceans, landfall, and ensuing deadly devastation are described in this chapter, which pays particular attention to the Sumatra Tsunami of the Indian Ocean that occurred on 26 December 2004. Much of the discussion is centered on the observations made in Sri Lanka, where close to 27,000 people lost their lives and another 4,000 remain unaccounted for. The tale of the Sumatra Tsunami in Sri Lanka typifies the mighty destructive forces of nature that control large-scale disasters, the unpredictability of natural phenomena driving such disasters, and the uncontrollability of their manifestation. However, the destructive aftermath could have been mitigated through better alertness and preparedness; education; preservation and reinforcement of natural defenses; sound design of coastal infrastructure; coordinated relief efforts; unselfish corporation across ethnic, social, and political fabrics; and scientifically based reconstruction policies. Inadequate scientific knowledge has been a bane of responding to tsunami disasters, and this chapter highlights some of the key issues for future research.

Introduction

In Japanese, “tsunami” is synonymous with the term “harbor wave” because it creates large wave oscillations in harbors and enclosed water bodies.