Ministry of Environment and Natural Resources Department of Meteorology Tsunami 26th December 2004 Introduction

If the epicenter of an earthquake is below the ocean it may produce seismic waves called tsunami. Such waves will not be produced if the earth displacement is primarily lateral and not vertical. For example, a severe earthquake having Richter magnitude of 7.7 occurred in Peru in May 1970. The epicenter of this earthquake was 25 miles off shore, but there was no significant tsunami associated with this earthquake. On the other hand, in November 1975, there was an earthquake of magnitude 7.2 on the island of Hawaii. The epicenter of this earthquake was right on the shoreline, where a wave was generated seconds after the earthquake, having height of over 20 feet (6 meters) above the normal water level. The height of this first wave diminished rapidly along the shoreline, roughly in proportion to the distance from the epicenter, so that on the far side of the island it was only about 3 feet (1 meter).

The first indication of a tsunami is generally a severe recession of the water, which is shortly; followed by a returning rush of water that floods inland a distance depending on the height of the wave. The recession and return of the water continues at intervals as each wave of the usual series arrives at the beach. These tsunami are long period waves that may travel great distances from the point of generation. Landslides or volcanic eruption could also generate tsunami.

The wavelength of tsunami waves are about 10 kms or more (may be long as 100 kms) and be as far as one hour apart. They are able to cross entire oceans without great loss of energy. Traveling speed of tsunami is depending on the depth of the sea. When the ocean is deep (5000m) tsunami can travel on the surface at speed of 800km per hour. When the depths are 500, 100 and 10 meters travelling speeds are 250, 100 and 36 km/hour respectively. Since the wavelengths are very long on the surface of deep oceans, they are not noticed by sailors. At the point where the earthquake occurs in the ocean, the height of the wave is proportional to the vertical movement of the ocean floor. As it travels in the deep ocean it behaves as shallow water wave and these waves are not visible on the sea surface. As the waves reach the coastal area, the speed is reduced to tens of kilometers per hour. Depending on the coastal morphology, the wavelength is reduced as it approaches the coast and wave height may reach as high as 35 meters or more.

Tsunami 26th December 2004 The Indian Ocean tsunami generated by the most powerful earthquake in decade on 26th December 2004 killed over 100,000 people and make millions homeless, making it perhaps the most destructive tsunami in the history. The epicenter of this extremely severe earthquake (Richter scale 9.0) was under the Indian Ocean near the west coast of the Indonesian island of Sumatra, according to the U.S. Geological Survey, which monitor earthquakes worldwide. Due to the violent movement of the Australian plate into under the Eurasian Continental plate this severe earthquake occurred at near the two different plate collision. The earthquake pushed up the Eurasian Continental Plate and the pushed up Eurasian Continental Plate lifted above enormous amount of sea water and making powerful big waves spreading all direction and hitting coastal area. Within hours waves radiating from epicenter slammed into coastline of 11 Indian Ocean countries, snatching people out to sea, drowning others in their homes or on beaches, and demolishing property from Indonesia to Africa. In the Sri Lanka coastal areas the height of the waves had been 2 to 10 meters.

Past Records of Tsunami

According to past records, more than 90% of the tsunamis recorded in the last 200 years have occurred in the Pacific Ocean region. Indian and Atlantic Oceans were generally regarded as tsunami-free, although some milder ones with wave heights about one meter have been reported in the coastal region. Therefore, tsunami-monitoring systems (which are very elaborate and expensive) have not been installed in the Indian and Atlantic Ocean regions. However, tsunami early warning systems have been existence in the Pacific region. It should be mentioned here that these systems are mainly focused to Pacific and at present only tsunami occurring in Pacific region can be monitored by these systems.

Present Situation in Sri Lanka

In Sri Lanka, Geological Survey and Mines Bureau is the nodal agency for earthquake related activities. It should be noted that only two seismometer facilities are available in Sri Lanka one is at Pallekelle which belongs to the Geological Survey and Mines Bureau and other one is at the University of Peradeniya. The one at Pallekelle is one of the automatic (unmanned) stations of the global seismic network maintained by the University of California, San Diego. When an earthquake occurs, the information received by this station is processed together with data obtained from other stations (at least three) elsewhere in the world by the US scientists. The resulting information about the magnitude and location of the earthquake is fed into USGS (United States Geological Survey web-site. On the 26th December 2004 information regarding occurrence of the earthquake near Sumatra had been updated in the web-site only after two hours. But a tsunami warning had not been given. Further, Pacific basin tsunami warning system had not detected a tsunami in the Indian Ocean since there are no buoys (sensors) there.

Immediate Action Since the establishment of tsunami warning system is very expensive and elaborate procedure, it would not be appropriate for Sri Lanka to have its own tsunami warning system. It is recommended that Sri Lanka should join an existing well functioning international tsunami warning system.

Long-term plan

A Regional System to be set up with the Indian Ocean States for the purpose of acquiring important information concerning earthquakes and tsunami close to our region.

G.H.P. Dharmaratna, Director General of Meteorology

Ministry of Environment and Natural Resources Department of Meteorology   Establishment of an Early Warning System on Natural Disasters   1. Introduction A majority of natural disasters experienced in Sri Lanka are weather related. Some of the major natural disasters experienced in Sri Lanka are, cyclones, heavy rainfalls leading to floods and/or landslides, lightning, tornadoes, coastal inundation due to high sea waves, and tsunami. Out of these, the frequency of occurrence of some disasters is extremely rare. Most devastating natural disaster experienced in the recent past is the tsunami that occurred on 26th December 2004, which resulted in the loss of over 30,000 lives in Sri Lanka. It has now become necessary as an urgent measure to assess the existing framework for natural disaster preparedness, reduction and management in Sri Lanka. This assessment should lead to the identification of the gaps in technology and human resources as well as infrastructure in the present set up. Once the gaps and other shortcomings in the present situation are identified it is possible to develop a strategy to address them. Based on their frequency of occurrence, natural disasters can be categorized as frequent, rare and intermediate as follows: Frequent Heavy rain and floods/landslides, Lightning, Tornadoes Intermediate Cyclones and Storm Surges, Coastal inundation Rare Earthquakes, Tsunami 2. Present Situation At present in Sri Lanka, there is no single authority empowered to handle issues related to all the disasters mentioned in the table above. For most of the disasters, a government institution is legally mandated to monitor the disasters which falls within their expertise. For example, Geological Survey and Mines Bureau is responsible for matters related to earthquakes while Department of Meteorology is responsible for weather related disasters such as tropical cyclones. The institutions responsible for matters pertaining to some of the major disasters are given in the following table. Institution(s) Disaster Department of Meteorology Cyclones and Storm Surges, Heavy rain, Lightning, Tornadoes National Building Research Organization (NBRO) Landslides Geological Survey and Mines Bureau (GSMB) Earthquakes National Aquatic Resources Agency (NARA), Sri Lanka Navy Ocean waves Irrigation Department Floods Though these institutions have legal and administrative mandate to monitor and issue warnings related to natural disasters, their efficient performance is affected by want of state-of-art technology, infrastructure and human resources.   3. Planned Action 3.1 National It is necessary to establish an effective early warning system not only for tsunami, which is considered to be a rare phenomenon but also for all the weather related disasters that are more frequent in the recent past such as flash floods, tropical cyclones, tornadoes, lightning etc. The most serious weakness in the present system is the unavailability of an effective information dissemination system to pass prior warnings to the public. This is one of the major reasons for the loss of large number of lives during the December 26th tsunami. The action to be taken by Sri Lanka should be compatible with the regional as well as global disaster management and early warning systems. It is hoped that the UN led initiatives would result in setting up an early warning system for the Indian Ocean. Taking this into consideration, it is necessary for Sri Lanka to plan its disaster Management and early warning systems. A number of plans have been suggested recently for the organizational framework for disaster preparedness, reduction and management. One of the suggestions is to,   (a). Constitute an Inter-Ministerial Committee for Disaster Preparedness and Management headed by H E the President and consisting of Ministers of all relevant line ministries. (b). Establish a Disaster Mitigation Authority under the Inter Ministerial Committee with legal and executive powers and consisting of representatives of all relevant organizations. (c). Establish a National Coordinating Committee on Technologies for Disaster Preparedness and Reduction. (d). Improve institutional infrastructure for collection, analysis and dissemination of information and warnings. (e). Advanced IT based warning system to facilitate timely protective activities such as evacuation etc. Another idea is to keep up with the existing organizational structure and to strengthen the identified institution by providing them with technological and infrastructural facilities and human resources.   3.2 Regional Sri Lanka is very much involved with the regional initiatives headed by the United Nations in setting up an early warning system for the Indian Ocean, especially to provide tsunami early warning capacity.   4. Suggested action As ideas are floating in various forms on how to develop the national disaster Management and Warning System. Therefore it is necessary to initiate a study with a view of receiving recommendations on an appropriate cost effective comprehensive system.   4.1 Suggested Study Group. This study requires the services of a multi disciplinary team of experts consisting of specialists in legal/institutional frameworks, information technology and communication, disaster management and relevant technology related to data gathering, analysis and dissemination of warnings to carry out a short term study and to propose suitable recommendations leading to the identification of the most appropriate system.   5. Terms of Reference The suggested term of reference for this study group is given below:   1. Examine the adequacy of existing legal and institutional frameworks of the agencies responsible for natural disasters and identify the institution(s) responsible for identified natural disasters. 2. Recommend an appropriate institutional infrastructure taking into consideration the strengths and weaknesses of existing agencies to maintain an effective system for data gathering. 3. Make recommendations on capacity development including technology needs and human resource development capacities. Study the existing warning/information dissemination procedures in each of the relevant institutions and to make recommendations for their improvement. 4. Assess the existing capabilities of the identified institutions and identify the deficiencies, which hinders them from performing their legally mandated tasks related to natural disasters effectively.   G.H.P. Dharmaratna, Director General of Meteorology