Natural Early Warning System for Tsunami

Natural Early Warning System for Tsunami Haryo Dwito Armono*, Suntoyo** * Lecturer, Head of Seabed and Underwater Engineering Laboratory Dept. of Offshore Engineering, Sepuluh Nopember Institute of Technology (ITS) Surabaya. INDONESIA. Phone/Fax: 031-5928105. Mobile: 081330459203. E-mail: armono@oe.its.ac.id ** Graduate Student, Environmental Hydrodynamics Laboratory Dept. of Civil Engineering, Tohoku University. 06 Aoba, SENDAI 980-8579, JAPAN on leave from Department of Offshore Engineering, ITS, Surabaya. Phone/Fax : 81-22-2177453. Mobile: 81-52217553 Email: suntoyo@kasen1.civil.tohoku.ac.jp Abstract Natural disaster of tsunami have occurred in Indonesia, Thailand, India, the Maldives and Sri Lanka after an earthquake measuring 9.0 on the Richter scale erupted, on Dec 26, 2004 of Sunday morning centered near the Indonesian island of Sumatra. The tsunamis washed away fishing villages and resorts throughout the region. The biggest tsunami on history has hit Aceh on Dec 26, 2004. In Banda Aceh as well as several coastal cities in Aceh, many people are not aware and care about the sign of nature before wave came. On the contrary, in a small island Simelue, the local people were aware of the sign of nature, and they know how to avoid the incoming wave and where to evacuate. The tsunami warning can be circulated via established communication systems to issue timely alarms to permit evacuation of coastal areas. Such high-technology warning system is surely needed high funding. Moreover, the sign of nature from animal behavior can be used potentially as a low-technology warning system to alert humans that only need low cost. Strange animal behavior can be observed before disaster. A lot of animals have sensory organs-super sensitive to sound, temperature, touch, vibration, electrostatic and chemical activity and magnetic field that gives them a head start in the days and hours before natural disasters. The paper will discuss various sign of nature before tsunami hits the coastal area and suggest the efforts taken by community to prepare and aware before tsunami sign occurs. Lesson learned from Tsunami survivor in Aceh will also be discussed and compiled. Keywords: Tsunami, Early Warning and Nature. Prper presented on International Seminar Disaster Early Warning Sysytem, Surabaya, 2005 1 Introduction As widely known, Indonesia located in four lithosperic plates (India-Australia, Eurasian, Philipine and Pasific) which are prone to the sesmic hazards. The movement of those plates make Indonesia has high sesmic activities, resulting in high earthquakes occurrence. The India-Australian plate is moving northward relative to southeastern Asia, subducting beneath the western through southern Indonesian islands along the Java trench and Timor trough (McCaffrey et al., 1985; Papadimitriou and Papazachos, 1994). The last interaction between Indo-Australian and Eurasian plates on December 26, 2004 erupted earthquake on 9.0 Richter scale and tsunami where Aceh and part of North Sumatra destroyed heavily. Most of Indonesian tsunamis (90.5%) are due to earthquake as noted by Latief et al (2000), while only 8.6% and 1.1% are due to volcanic eruption and landslide respectively. Figure 1 shows the earthquake and tsunami occurrence from 1600-2004 in Indonesia. As seen in the figure, most of the earthquake and tsunami occurred along Sumatra and Java where the subduction zone is found. (a) (b) Figure 1. Records of Earthquake (a) and Tsunami (b) location in Indonesia (ITDB, 2004) A tsunami is a natural phenomenon consisting of a series of waves generated when water in a lake or the sea is rapidly displaced on a massive scale. Earthquake, landslides, volcanic eruptions and large meteorite impacts all have the potential to generate a tsunami. Moreover, tsunamis are one of the most destructive forces in nature and can cause much loss of life, injury, and property damage. Tsunamis are usually produced by the uplift of the sea floor from a large magnitude subduction zone earthquake. The effects of a tsunami can be local or distant. Injury and loss of life can be minimized if coastal populations are warned that a tsunami is approaching. In the case of a local tsunami, the warning is usually the earthquake. However, after the occurrence of large undersea earthquakes, which will be instantly recorded on seismic monitoring networks Prper presented on International Seminar Disaster Early Warning Sysytem, Surabaya, 2005 2 worldwide, preliminary warning can be raised for coastal regions at risk of tsunami. Subsequent monitoring of sub sea pressure gauges can identify signs of tsunami occurrence. If increased water pressure is recorded, signifying the presence of a tsunami wave, full warnings can be raised. The tsunami warning can be circulated via established communication systems to issue timely alarms to permit evacuation of coastal areas. Such high-technology warning system is surely needed high funding. Man-made warning system can be costly or individually inadequate to cover all hazard areas (Darienzo et al, 2005). It should also robust enough to withstand a damaging earthquake and redundant if one fails. Therefore, the sign of nature from animal behavior can be used potentially as a low-technology warning system to alert humans is inexpensive. The various nature signs from nature and animals are discussed in the following sections. Natural Tsunami Sign The Natural sign of nature preceding the tsunami are earthquake, as most of the tsunamis are due to earthquake. However, not every earthquake triggers tsunami. Only the earthquake where its epicenter is in subduction zone, shallow, and located in the sea that has magnitude greater than 6,2 is possible to trigger tsunami. (Haryadi in Ikawati 2004a). The earthquake precursors has been listed and proposed in a project sponsored by International Association of Seismology and Physics of the Earth’s Interior (IASPEI). A total about 40 nomination were made and evaluated by a subcommittee. Wyss (1997) listed the occurrence including foreshocks, preshocks, seismic quiescence before large aftershock, radon decreases in ground water, and ground water increases. As the measuring technique preseismic phenomena are difficult, people try to consider the sensitivity animals. Beside earthquake, the abnormal sound before the arrival of tsunami also reported in some cases. A sentence “Earthquake, sea roar, then tsunami” written in the monument in Aomori Prefecture, Japan to memorize Showa Great Sanriku Tsunami (M=8.1) in 1933 (Shuto, 1997). Some people in Banda Aceh and Calang was also reported that they hear the strange sound and saw a strange object in the sea, before they realize that was a black huge wave with its whitecaps coming to them in a high speed (Suryopratomo, 2005). The Japanese Council for Earthquake Disaster Prevention (Shuto 1997) after Showa Great Sanriku Tsunami recommended the following: Since there will be usually at least 20 minutes between the generation of a tsunami and its arrival at the Eastern Sanriku Coast, instrumental or empirical observation of tsunami related phenomena will help to know the approach of a tsunami. Prper presented on International Seminar Disaster Early Warning Sysytem, Surabaya, 2005 3 The following are the tsunami related phenomena: Table 1 Classification of sound Sound Heard on the sea 1. Sound caused by the earthquake or seaquake 2. Sound from land Sound Heard on the Land 1. Sound heard at the time of the earthquake 2. Sound caused by the ebb of the tsunami 3. Sound caused by the coming tsunami 4. a. Continuous sound at the site b. Suddend sound at the site c. Sudden sound at distant sites Sound where the source is unknown According to Shuto (1997), the fisherman while they are on the sea, often hear the sound at the time of earthquake. E,g the sound when the sea bottom cracked or rupture. Although they are not aware that the tsunami has hit the coast, they also sometimes hear the sound comes from the land. On the land beside the sound at the times of earthquake that is widely heard at very distant places from its epicenter, the sound of gravel movement on the beach during enormous ebb was also heard. This type of sound is heard as “the wind blows through a thick bamboo grass” or “the sound of rapid stream”. When the tsunami coming, the continuous sound is expressed as a huge running locomotive or big truck. This is due to spilling or breaking tsunami waves. The sudden sound heard by the witness due to plunging wave at the beach described as “a sudden fall of thunderbolt” or “a very big inexpressible sound”. At the distant location the sound of tsunami is described as “a distant explosion”, a distant thunder or a distant canon. Some of the sound is caused by tsunami impact to the coastal cliffs. Another sign that are obviously seen before tsunami hit Aceh is the enormous ebb or rapid run down in the coastal area. As many people are not aware and some of them try to collect fish, the big wave rolled them while they’re busy with their catchment. (Gunawan, 2005, Ikawati, 2005, Radius, 2005). Strange animal behavior can be observed before disaster. A lot of animals have sensory organs-super sensitive to sound, temperature, touch, vibration, electrostatic and chemical activity and magnetic field that gives them a head start in the days and hours before natural Prper presented on International Seminar Disaster Early Warning Sysytem, Surabaya, 2005 4 disasters. Many fishes are sensitive to low-frequency vibrations and detect tremors long before human. Elephants are also extremely sensitive to ground vibration. Moreover, some animals may have heard the tsunami coming from the moment the quake erupted under the ocean. Species of birds, dogs, elephants, tiger and other animals can detect infrasound-frequencies in the range of 1-3 Hertz, compared with humans in the range of 100-200 Hertz The animals ability to detect earthquake or tsunami in advance are noted by Aceh survivors. As reported by Brigadir General Suroyo Gino saw the white flocks birds flied away from the coastline few minutes before tsunami came. The Vice Director of Sri Lankan Wildlife, Ratnayake also surprised that not any single elephant and rabbit found dead while about 24.000 people dead in his country. “It looks that they can smell the danger”. The wildlife experts Clive Walker supported his view, as birds was found as one of the most sensitive animals which can sense the changing of natural phnomena (Suryopratomo 2005). Researcher in Japan, Kiyoshi Shimamura, a public health doctor, believes dogs may be a more fruitful prediction tool. Shimamura examined the records of dog-related complaints such as bites, excessive barking or other unusual behavior at 12 public health centers in parts of western Japan affected by the Kobe earthquake. He said such complaints jumped by about 18 percent in the two months before and after the magnitude-7.2 quake. The study indicating erratic behavior in dogs, such as excessive barking or a higher than usual tendency to bite, may be a quake harbinger. (AP, 2003) Kirschvink (2000) noted four phenomena preceeding earthquake perceived by animals: 1) ground tilting, 2) humidity changes, 3) electrical currents, 4) magnetic field variations. Further research on the animals behavior due to the above phenomena prior to earthquake is suggested. Ground tilting prior to strong earthquake have been reported in Japan and China (Kirschvink, 2000). In some cases, the magnitude is in the range of micro degree, where human cannot perceive it as Birsdorf et al (1996) noted that normal human respond to 6o or more. Animals for example rodents or rats have more sensitive vestibular system in their inner ear than that of human to detect tilting. (Lindenlaub, et al, 1995). It is noted that theres a change in ground water level prior to earthquake that associated in local humidity that animals can detect (Kirshchvink, 2000). As groundwater level rises significantly due to preseismic dilatancy, the some pore spaces underground is displaced by water increasing the humidity of air in soil and the surface layer of top soil. The spiders and insects pose hygrosensitive sensilla to detect humidity and temperature fluctuations (Sayeed and Benzer, 1996; Tichy and Loftus, 1996). Rodents has proved to be able to Prper presented on International Seminar Disaster Early Warning Sysytem, Surabaya, 2005 5 detect seed catches buried in dry sand based on variation of only few percent water contents (Vanderwall, 1933). Trisbutch (1982) notes that some of the behaviors displayed by animals before earthquake resemble their prestorm behavior, so this may be a component in their preseismic behavior. Derr (1973) noted that electrical light have been reported before, during and after earthquakes. The light ignited presumably, by some form of crack propagation coupled with ion flow and perhaps fluid movement prior and during the earthquake. Aquatic animals such as sharks, rays, and some fish often have exquisite electrical sensitivity due to specialized organs used both for communication and prey location (Bullock, 1982). Sharks and rays have ability to perceive nanovolts changes in electrical fields. (Kalmijn, 1974). Nocturnal animals would also have no difficulty detecting earthquake light visually. Ultra Low frequency magnetic field variations are included in the list of phenomena in the IASPEI List of Earthquake Precursors (Wyss, 1997) . Birds have been known for a long time to be disoreinted as magnetic anomalies (Walcott, 1978), as dolphin an whale strand / trap in the shalow coast usually happen at magnetic anomalies along coastlines (Klinowska, 1985). Furthermore, Trisbutsch (1982) reported of unusual overflowing behavior of bees about 15 minutes prior to the strong earthquake. It is proved from laboratory experiments that honeybees geomagnetic sensory system has evolved to level where they can detect the magnetic anomalies before earhtquake (Kirscshvink, 2000). Natural Warning System Based on information collected on animals sensitivity and natural signs preceding earthquake or tsunami, a natural warning system can be develop. The first thing to do is to lists the natural signs and animal behavior proceeding tsunami and earthquake. This list can be compiled from the tsunami survivors or scientific papers. Emphasis are placed on the behavior of domestic animals or pets which daily seen. This effort should also be accompanied with the preparation of the map of tsunami and earthquake prone areas. Therefore, from the natural sign lists, some animals to look after could be suggested -especially for those who live in the hazard prone areas- to give their master warning before earthquake or tsunami. Next is public education, i.e: to prepare community before the tsunami coming. This includes education on natural signs prior tsunami, the tsunami itself, and planning for evacuation route, therefore each individual knows what to do when tsunami or earthquake occurs. Picture 2 shows the evacuation route sign in Crescent City, California. Prper presented on International Seminar Disaster Early Warning Sysytem, Surabaya, 2005 6 Figure 2. Tsunami Evacuation Sign in Crescent City, California (Dangler, 2005) Good education example are found in Simelue island, where people run to the hill as they knew that there was a rapid run down in the coastal area following an earthquake. It looks that they have learnt from the 1935 Tsunami (M=8.1), so the victims in Simelue is less than other districts. The older people in the Simelue island told the tsunami 1935 story to their children and grand children, so they know what happened and what to do when 2004 tsunami striked them. As populations constantly change day by day, public education is never-ending effort. The National Tsunami Hazard Mitigation Program (NTHMP) in the United States, put education program as the major and first effort of reducing vulnerability to tsunami hazards (Dengler, L (2005). The program was develop after the 1992 7.1 (Mw) earthquake in Humboldt County, California. The workshop of The Tsunami Hazard Mitigation Implementation Plan in 1996 also defined education as the primary tool for reducing losses from a locally generated tsunami and it identified three primary education needs of people and communities in potentially hazardous zones: • Recognizing the signs and impending tsunami • Understanding what areas are at risk • Knowing how and when to evacuate In the first year after NTHMP established, a Strategic Implementation Plan was created to Prper presented on International Seminar Disaster Early Warning Sysytem, 7 Surabaya, 2005 asses existing mitigatin programs and materials, formulate mitigation strategies, and set priorities for projects (Dengler, 1998). The Strategic Plan defines twelve education planning elements, including print, electronics, audio and video materials, posters and signs, curriculum programs, museums and information centers, public relation efforts, workshops, and other public forum targeted for a variety of audiences. The detail of educational efforts of the NTHMP can be found in Dangler, 2005. Conclusion There are two efforts on developing the natural tsunami early warning system. The first is to understand and examine the nature sign such as earthquake, animal behavior prior to earthquake or the incoming big waves. The second is the effort taken way far before the tsunami occurs. Such as promote the awareness and preparedness of the community in the coastal areas whenever the tsunami came. This includes the evacuate plan, zone planning, and implementing tsunami building code to reduce the tsunami effects. Based on the local information and tsunami survivors, the preparedness for the next earthquake or tsunami can be increased to higher level. Local governments, especially whose areas prone to tsunami, need to inform their people and community the tsunami or earthquake signs and provide them with evacuation route and shelters. 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