2004 Indian Ocean Tsunami
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Author:  Anand Leo [ Sat Jun 26, 2010 3:34 pm ]
Post subject:  2004 Indian Ocean Tsunami

The December 2004 Sumatra – Andaman Earthquake and Tsunami Preparedness of Sri Lanka. Part I: Tsunami Earthquakes.


The Sumatra-Andaman earthquake on 26 December 2004 is the second largest and generated the most devastating tsunami in the recorded history. The real-time seismic monitoring measured a moment magnitude of 9 and subsequent studies using very long period waves determined a moment magnitude of 9.3. The total death toll was in the order of 300,000. Indonesia and Sri Lanka are the most severely affected countries by the tsunami. The tsunami was generated by a rare mega earthquake that occurs in a subduction zone fault line. Tsunamis are long wave length, small amplitude waves in the deep ocean hydrodynamically called shallow water wave, and when shoal in the continental shelf, increase the wave height tremendously to inflict savage destruction by inundating the coastline. In spite of Sumatra-Andaman active fault line there are no records of destructive tsunami in the Indian Ocean in modern history. Therefore prior to December 2004 a formal tsunami warning system did not exist in the Indian Ocean. This paper is written in two parts. The part I presents the concepts and fundamentals of seismology and tsunami. The part II presents an overview of the December 2004 Sumatra-Andaman fault rupture, the ensuing Indian Ocean tsunami and consequent tsunami preparedness of Sri Lanka.

The December 2004 Sumatra – Andaman Earthquake and Tsunami Preparedness of Sri Lanka. Part II: 26 December 2004 Indian Ocean Tsunami and the Consequent Tsunami Preparedness.


The Sumatra-Andaman earthquake on 26 December 2004 created the most devastating disaster caused by a tsunami in the recorded history. It was the second largest earthquake in the instrumental record and measured an estimated moment magnitude Mw of 9.1-9.3 (Bilham, Sci 1126, Lay et al Sci 1127). The tsunami in the Indian Ocean inflicted inconceivable scale of devastation for people on more than two third of the 1500 km long coastline of Sri Lanka in less than 2 hours around 9 am (local time) on 26 December 2004. In average tsunami height at the shoreline was more than 5m, in many places the maximum height was greater than 10m and the maximum height estimated in the east coast near Batticaloa is 15m (Dias, ICE, Satake). In the south coast maximum runup height of 13 has been reported runup height is 13m (Liu & Lynett et al). The inundation distances are in average about 100m but in few places reached up to 3 km. As Sri Lanka had no living memory of tsunami hazard and as there was no formal tsunami warning system in the Indian Ocean, Sri Lanka was not prepared for averting the full brunt of the calamity. Hence the total death toll was more than 35000. The total cost of damage is over $1.5 billion. Housing, commercial and public buildings, tourism, coastal road, rail, bridge, water supply and irrigation infrastructure suffered severe damage. Coastal ecosystems, mainly coral reefs, mangroves, dunes and beeches were also severely damaged and a vast amount of debris was dumped on land.

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