I Gede Hencrawan. Bambang Sukresna and Yasuhiro Sugimori

PRESENT UNDERSTANDING OF (Applications of Data from Field to Satellite Observations)

I GEDE HENDRAWAN1, BAMBANG SUKRESNO AND YASUHROSIGIMORI1

Abstract Application of data from field to satellite observation and simulation has been made as present understanding of Aceh tsunami. Tsunami has attracted attention after struck Aceh in December 26th 2004. generated by a strong earthquake with magnitude Mw=9.0. The earthquake triggered giant tsunami waves that propagated throughout the Indian Ocean, causing extreme inundation and destruction along the northern and western coast of . Within hours, the tsunami devastated the distant shores of Thailand to east as well as Sri Lanka. India and Maldives to the west. The tsunami also caused deaths and destruction in Somalia and other nations of East Africa. The tsunami was recorded on tidal stations throughout the Indian Oceans in worldwide. Unlike the Pacific, tf\c Indian Ocean does w* y«v have a wstwwk. of deep-ocean pressure sensws. and so coastal tide gauges provide the only direct measurement of Indian Ocean tsunami amplitudes. We had many lessons and basic knowledge which had already been learned from this tragic event in the Indian Ocean. Many more lessons should be learned in the near future as this tragedy unfolds and reveals many failures to value and protect human life in this neglected region of the word.

Key word: Tsunami Earthquake, Indian Ocean, Aceh

1. Introduction submarine volcanic eruptions have the potential capability to produce awesome About two-thirds of earth is covered tsunami waves. The great Krakatau by the waters of the four oceans. The volcanic eruptions in 1883 had generated Pacific Ocean is the largest in the world, giant waves reaching heights of 125 feet covering more than one third of total above sea level, and killed thousands of surface area of our planet. The Pacific people and wiping out numerous coastal Ocean surrounded by a series of mountain villages. chains, deep ocean trenches and island arcs, that is some times called a 'ring of Not all earthquakes intend lo generate fire'. The great size of the Pacific Ocean a tsunami. In order to generate the and the large earthquake associated with tsunami, the earthquake must occur the 'ring of fire' combine to produce underneath or near the ocean, and be large deadly (Anonym. 2006). and create movements in the sea floor. The • tsunami can occur in all oceanic regions of Tsunamis shall also produce seismic the world, but in the Pacific Ocean, there sea waves, or incorrectly tidal waves, are frequent occurrences of large and generally caused by earthquakes, less destructive tsunamis because of many commonly by submarine landslides, large earthquakes along the edge of the infrequently by submarine volcanic Pacific Ocean. eruptions and very rarely by a large meteorite impact in the ocean. The

Center for Remote Sensing and Ocean Science (CReSOS), Udayana University

RhMO'lh ShNSlMi \Nl) \ \RTH SCIENCES September2007 Volume4 \\3 Present Understanding of Aceh Tsunami (Applications Data from RekJ lo Satellite Observations)

In ihc open ocean, a tsunami uses to II. Fundamental Study of Tsunami be less than few feet high level at the Fundamental knowledge of the surface, but the wave height is increasing tsunami: rapidly in the sallow water of the coastal area. The tsunami energy extends from the 1. It is primitively created by the surface to the bottom of the deepest water. deformation of the sea bottom configuration due to the great In the deep oeean. a destructive earthquake. tsunami can be small -often for only few feet or less in height- and cannot be seen, 2. If the magnitude (M) of the earthquake nor can be felt by ships. Some times the is less than 6.9, the tsunami never coastal water is withdrawn into the deep occurs. ocean just before the tsunami strikes. 3. In general, the magnitude of the When these occur, more shorelines may be tsunami is corresponding to the exposed than that of even at the lowest magnitude of the sea bottom tide. This major withdrawal of the sea earthquake, but not always. should be laken as a wanting of ihc 4. The tsunami will not occur only by the tsunami waves that will follow soon. earthquake, but also by the explosion of volcano, the landslide al the sea Where the ocean is over 20,000 feet bottom and the nuclear explosion. deep, an unnoticed tsunami can travel at 5. The most frequent Tsunami has the speed of a commercial jet plant-, nearly occurred at the coast of the Pacific rim 600 miles per hour. It can move from one countries, and in no more other place side of the Pacific Ocean to another side in or called "The Circum-Pacific less than a day. This great speed makes it Earthquake Belt". important to be aware of the tsunami as soon as it has generated. Scientists can The history of tsunami in the world predict when the tsunami will arrive. The reveals that the most frequent tsunami has tsunami travel much slower in shallow occurred at the coast of the Pacific rim coastal water which is their wave heights countries, and in no more othtr place as begin to increase dramatically. the Circum-Pacific Earthquake Belt. Repeating tsunamis attack countries like The offshore and coastal features can Japan. Alaska, Taiwan, Philippine, determine the size and the impact of the , Peru, Chile, Colombia and tsunami waves. The reefs, bays, entrance slightly attack Greek. Black Sea rim to rivers, undersea features and the slop of countries, Portugal, Spain. the beach combine to modify the tsunami as its attack. When the tsunami hit the The generation and the traveling of the coast and moves inland, the water level tsunami at the sea surface are exactly can rise many feet. In extreme cases, the corresponding to the deformation of the water level has risen to more than 50 feet sea bottom configuration. The velocity of for the tsunamis of distant origin and over tsunami can be counted by this follow 100 feet for the tsunamis waves generated equation: near the epicenter of earthquake. The first wave may not be the largest wave in the V= = 3.13*.13* H series of the tsunami waves. The flooding of the tsunami can extend inland by 1,000 where: feet or more, covering large expanses of g : acceleration of gravity force 9.8 m land with water and debris. .sec'1 H : depth of sea (m)

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If the point of ocean earthquake is far 1) Air-borne: Radar, Aerial from the coast, 10 to 20 tsunamis will Photograph arrive to the coast and after that, the 2) Satellite : Optical Sensor. Active biggest tsunami will attack the coast. The Microwave Radar wave height equated by the "Rule of d) Wide spatial coverage. Lack of Green*'which tsunami height is amplified immediacy. to be inverse proportional to root The tidal observation (tidal station) quaternary of depth of ocean: 4-jH measures sea surface level including with Moreover, the tsunami which enters into disturbance; consist of aqueduct, tidal the bay will be superposed with the wave well, static surface level, and recorder, as of peculiar oscillation of the bay. and shown in figure 1. The supersonic tsunami produce much higher Tsunami. sensor as shown in Figure 2 settled just above the ocean surface from the land It is very important never to be in platform and measures the tsunami height carelessness that the highest Tsunami will by the time lapping of supersonic wave attack coast after 10 to 20 waves. When from sensor to the sea surface and we have got earthquake, we can never corrected by the normal tidal level. come close to beach in anytime. Aceh Tsunami also shows this danger. Result The alert system by the large scale shows us that The tsunami from 0 m to 5 tsunami sensor detects the tsunami as m gives damage for house, but not much people. However, the tsunami which is hydraulic pressure on the land area and the more than 5-10 m has killed many people alert for the large scale tsunami intrudes and given a bigger damage for many into inland area and is automatically houses washing away. Other damage is received by the master data control center damage for bridge, harbor ship, road, train using the remote data link in Disaster line, farming field. Prevention Center and is followed by an immediate warning to the people by using the alarm or warning and also trough the telephone list. III. Observation System for the Tsunami and Prediction GPS tsunami sensor uses GPS antenna on buoy to determinate the occurrence of a) Field Observation (in-situ observation) tsunami precisely by the satellite in cm 1) Tidal Observation (Tidal Station) order. The tsunami is recorded as the time 2) Supersonic Tsunami Sensor series of antenna location. The decision of 3) Large Scale Tsunami Sensor method used in this system determines the 4) GPS (Global Positioning System) accuracy of tsunami observation where a Tsunami Sensor single method gives the accuracy approximately 30 m. the differential b) Real time monitoring, small spatial method increases accuracy to 3 m. The coverage real time kinematics gives good accuracy c) Remote Sensing (estimation of to 3 cm and finally the static method gi\es disaster) sharp accuracy up to 1 cm.

REMOTE SENSING AND EARTH SCIENCES September 2007 Volume 4 115 Present Understanding of Aceh Tsunami (Applications Data from Field to Satellite Observations)

Fig. 1. Tidal Station

Fig. 2. Supersonic Tsunami Sensor

116 REMOTE SENSING AND EARTH SCIENCES September 2007 Volume 4 I Gede Hendrawan, Bambang Sukresna and Yasuhiro Sugimori

The simulation of tsunami using model movement of tectonics plate and the gives understanding of tsunami initial friction of each plate in boundary to the water height as modeled by university of Northeast of plates between the Pacific Tohoku, Japan. This model also reveals and India-Australia plates. The plates the maximum height and the traveling move less than 1 cm/year to the Northeast. time of the tsunami. The sea surface level Several big tsunamis have occurred at developed by model has relatively positive the trench line in the Indian Ocean by the correlation with the sea surface level stress of plate's motions. In 1815 tsunami recorded by the satellite such as Jason-1 killed almost 10,000, in 1883 almost satellite, 36,000 people were killed. In 1917 around 15,000 people were killed. 1992 around IV. Overview of Aceh Tsunami 1,000 people were killed. 1994 tsunami has killed 238 people. 1996 there are 9 Tsunamis are not as common in the people killed, and the biggest number of Indian Ocean such as in the Pacific Ocean. victim killed by tsunami in Indonesia As compared to the average eight tsunamis happened in 2004 where around 130,000 per year in the Pacific, the Indian Ocean people were killed. has one in three years or so. A catalog of tsunami shows about ninety tsunamis in Aceh (Nanggroe Aceh Darussalam) is the Indian Ocean out of which over 70 a province located on the top of northern tsunamis are from Sunda. Some of 20 area of Sumatera. is the tsunamis are reported from the rest of the capital city of Aceh (on 5°31' North and Indian Ocean, though source region of five 95°25' East, with an elevation of 21 m). of them may be in Sunda arc. Hence, Relative to most of Indonesia, it is a eighty percent of the tsunamis of the religiously conservative area, rich with Indian Ocean originate in Sunda arc natural resources, particularly oil and gas covering Java and Sumatra, Rastogi .The population of Aceh are 4.5 million (2006). The tsunami often occurs in (2004) or 3% of the Indonesian Indonesia Region developed by the population.

170 Ma

Fig. 3. Plate tectonic in Indonesia archipelago. Boundary of Plates between Pacific and India-Australia plates, Plate moves less than 1 cm/year

REMOTE SENSING AND EARTH SCIENCES September 2007 Volume 4 117 Present Understanding of Aceh Tsunami (Applications Data from Field to Satellite Observations)

Fig. 5. Number of Earthquake from Seismic Data on December 26th 2004 (Sources: Geophysical and Meteorology agency of Indonesia) On December 26, 2004, 00:58 (UTC), India plate subducts beneath the overriding 07:58 (Local Time, Indonesia), a great Burma plate. Figure 6 shows the tectonic earthquake occurred off the west coast of setting of the northern Indian Ocean. The northern Sumatra, Indonesia. The main shock occurred off the west coast of magnitude of this earthquake was 9.0 and Sumatra Island and the aftershocks this was the fourth largest earthquake in extended northward along an the world since 1900. The earthquake approximately 1,000 km rupture zone. occurred on the plate boundary where the

118 REMOTE SENSING AND EARTH SCIENCES September 2007 Volume 4 I Gede Hendrawan, Bambang Sukresna and Yasuhiro Sugimori

Fig. 6. Regional map of Tsunami Afected Area (UNOSAT)

The teleseismic waveform study by slow source processes of the event and Amnion et al. (2005) shows that the tsunami generation. rupture expanded at a speed of about 2.5 V. Aceh Tsunami and Environment km/s in a north northwest direction, Damage extending 1,200 to 1,300 km along the Andaman trough. They also suggested that The Sumatra Earthquake and the th the some slip in the northern 400 to 500 Indian Ocean Tsunamis of December 26 , km of the aftershock zone occurred on a 2004 have been described as creating one time scale beyond the seismic band. The of the "worst disasters" in recent history. Earth's free oscillation study by Park et al. Twelve countries around the Indian Ocean (2005) shows that the seismic moment of were affected. Indonesia, Thailand, India the earthquake was 6.5x1022 Nm (Mw and Sri Lanka had the largest numbers of 9.15), with rupture duration of 600 deaths and displaced people. • seconds. Lay et al. (2005) also indicated that additional slow slip occurred in the The tsunami that accompanied this north over a time scale of 50 minutes or earthquake propagated over the entire longer. All of the above results suggest Indian Ocean and caused extensive and that the unusual slow slip nature was a part significant damage. The reported number of the source process of the 2004 Sumatra- of casualties were approximately 300,000: Andaman earthquake. However, the 230,000 were killed in Indonesia qualitative analysis of the slow slip nature (earthquake and tsunami), at least 29,000 using seismological data is limited, as were killed in Sri Lanka (tsunami), more shown by Ammon et al. (2005). The than 10,000 in India (tsunami), more than crustal deformation and the tsunami 5,000 in Thailand (tsunami), and 82 were waveform data were essential to study the killed in the Maldives (tsunami), and more than 22,000 are still missing.

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Population Density of

Fig. 7. Tsunami landing up Aceh City on 26, Dec, 2004. UNOSAT, using GLCF, JPL, USDS data, blue line showing arrival area of the tsunami at max. 30 m level: Inside of mosaic, color of white; 30 -50cm land level, light brown; 50cm - lm land level, red; 5 - 25 m land level

Banda Aceh is the provincial capital damaged badly by the flood. Most of the and the largest city in Aceh. It is located dead and missing people in Banda Aceh on the northwest tip of the Sumatra Island came from the zones mentioned above. and is surrounded by the Aceh Besar The province of Aceh is district. Banda Aceh took a direct hit from geographically divided into four areas: (1) the tsunami. The residential zone, Banda Aceh and its adjoining district, (2) spreading between the coastline and the the southwest coastal region, (3) the north city centre, was completely destroyed. The coastal region and (4) the interior region. commercial zone and government offices The detail numbers of victims by regions escaped total destruction but were are shown in the table below.

Table 1. Number of Tsunami Victim in Aceh (Source: Disaster Countermeasures Provincial Office, 24 January 2005) Aceh Banda Aceh Southwest North Coast Interior Province & Adjoining Coast

Population 4,263,603 550,532 953,377 2,250,017 509,677 Dead 100,258 62,273 29,164 8,596 225 Missing 129,549 123,492 3,858 1,922 277

Displaced 417,124 150,858 120,125 140,932 5,209

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Fig. 8. Post Tsunami image along West Coast of Aceh Province: 26, Dec., 2004, LANDSAT-ETM, UNOSAT (UNITAR), using data of GLCF, JPL, USGS, Value of elevation; 20 m, Tsunami landed up to more than 4km and destroyed house, road and bridge

The southwest coastal region, which The tsunami not only destroyed towns consists of the districts of Aceh Jaya, Aceh and villages in the region but also severed Barat (West Aceh), Nagan Raya, Aceh the road and destroyed some bridges along Barat Daya and the island of Simeulue, it. Towns and villages were totally isolated was closest to the epicenter of the and accessible only by boat or by earthquake which triggered the tsunami. helicopter. This caused a great deal of The only road accessible by car ran along difficulty in correctly ascertaining the the coastline and a number of towns and damage in the region. It also caused a lot villages were located along it. of trouble for aid workers working in the region.

Fig. 9. Partially damaged family house located about 0.9 km inland in Banda Aceh. Left side is shore and right side inland. Numerals indicate inundation depths

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Except for several fishing villages in on 23 June 2004 displays existing land this region, the tsunami did not seem to cover and terrestrial matter before ruined inflict severe damage, especially in by tsunami in 26 December 2004. The comparison to other regions in Aceh. Quick Bird satellite received post tsunami Nevertheless, the local society was greatly image of Aceh region and showed \ne affected by the tsunami because survivors huge damage caused by tsunami. Many from the southwest coastal flocked into the places disappear, building and road access towns and villages in the north coastal shattered, coast land eroded. Tsunami was region. Moreover, the perception that the landing up 4 km from coast. region Was less affected by the tsunami Map of Banda Aceh Region 28 discouraged relief aid from reaching the December 2004 shows almost whole of region. It could cause future social Banda Aceh destroyed by tsunami. It is in uncertainties if relief aid continues to be accordance with the location of Banda concentrated only on other regions. Aceh that laid under 30 m elevation as well as towns which fall within this zone. VI. Aceh Tsunami from Satellite Only few part of Banda aceh and vicinity The satellite image of Quick Bird located above 30 m, so the damage caused shows the damage caused by tsunami in by tsunami spread widely. Aceh 2004. The satellite image received

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The situation in Banda Aceh post reveals the damage of important building, tsunami also referred by other UNOSAT hospital, mosque, and water infrastructure. map. The space map was made on basis of Banda Aceh after 2 years Tsunami satellite image SPOT 5 (2.5 m attacked can show by Alos data image pansharpened) from 30 December 2004. using AVNIR2 sensor. AVNIR2 sensor This map shows the damage of urban area, has spatial resolution 10 m. This image forested and sparsely inhabited area, shows clearly that the urban area was cultivated area, rice paddies, and also almost recovered; it is indicated by the changes of coast line, river, channels and white circles that some of houses were inland water, stream. Other damages constructed. Figure 13 shown that old caused by tsunami also occurred by coastline has been changed by Tsunami communication network such as railway, attack. Using PRISM sensor which is has bridges, and access road. This map also higher spatial resolution 2.5 m, also can shows clearly reconstructed house.

Fig. 11 Spot-5 Satellite Data after Tsunami

Fig. 12. Banda Aceh after 2 years Tsunami by AVNIR2 sensor of ALOS Data (pseudo color)

REMOTE SENSING AND EARTH SCIENCES September 2007 Volume 4 123 Present Understanding of Aceh Tsunami (Applications Data from Field to Satellite Observations)

Fig. 13. Coastline change in Banda Aceh can be shown by AVNIR2 sensor of ALOS Data (RGB-true color)

Fig. 14. Banda Aceh after 2 years Tsunami by PRISM sensor of ALOS Data. Reconstructed house along coastal area

VII. Prevention of Tsunami Hawaii, the center of the Pacific ocean, but There were many tsunamis warning in the F area including Indonesia center in the world. In the Pacific ocean (including Aceh) it is planned to establish there are 5 tsunami warning areas split to the center. This is one of the reasons that area A, B, C, D, E of which World Aceh had a big tsunami without any Tsunami Warning Center is located at warning and killed numbers of people.

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Fig. 15. Network of Tsunami Warning System

The network of Tsunami Warning should not be built in the Center has a system of Tsunami vulnerable areas. The existing observation; using the in-situ buoy system tourism facilities, shrimp farms and tide gauge at the coast in the Pacific and aquaculture infrastructure Tsunami warning area and send the real located in areas at risk should be time data to WPTC through the satellite. relocated. On the other hand, the real time Tsunami 1.2 The provision of appropriate data are informed to each country in WTC incentive packages and the area through the satellite. attractive livelihood The other important thing is to opportunities to encourage establish a local organization network in coastal communities to abandon each country with the aims to pronounce settling in vulnerable locations the occurrence of tsunami, to inform the and/or living in poor-designed coming of tsunami to the local citizen in houses, particularly along low- coastal zone and to take shelter from lying areas of the coast. tsunami. 1.3 The maintenance of Thanawood (2006) explain the environmental and ecological prevention and mitigation of tsunami as stability of the coastal areas follow: through the enrichment of mangrove and beach forests to I. Mitigation measures act as the first line of defense 1.1 The establishment of land use from the tsunami waves , and plan for coastal areas based on rehabilitation of lost and vulnerability assessments and degraded coral reefs and sea risk analysis. Critical facilities grass beds to help stabilize the such as schools, hospital, hotels coastline and prevent beach or high occupancy buildings erosion.

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1.4 Reconstructing the removed 2.4 Raising ihe awareness of the coastal sand dunes and coastal communities about the protecting the remaining sand dangers posed by a deadly dunes to act as a barrier against tsunami. Brochures, posters, ihe giant waves. The creating of calendars, and announcements the butter zones along the on the radio and the television coastlines to protect coastal can be used to stimulate public communities from tsunami awareness. waves is established. The buffer zones or green belts can be 2.5 Construction of a tsunami created through the memorial to commemorate areas devastated by the 2004 tsunami. establishment of the buffer strips The memorial would become a of between 300-400 metres, major attraction for both locals planted with mixed vegetation. and visitors, helping them to 2. Preparedness measures understand the coastal geomorphology and ecosystems, 2.1 The installation of a local and to remind them of the tsunami warning system, which disastrous consequences of the includes siren towers at popular December 2004 tsunami events. and crowded beaches, and a tsunami warning sensor floating offshore in the most vulnerable VIII. Conclusion provinces. Tsunami has a great deal to be 2.2 The development of education concerned by the development of programmed through schools fundamental studies of seismology and and universities to educate tsunami, the establishment of the World vulnerable coastal communities Tsunami Warning, the establishment of about the nature and processes system in Indian Ocean and Local of the tsunami hazard and how Network, the development of satellite to protect themselves at the time observation system in real time and finally of the impact as well as the establishment of Tsunami defense importance of mangrove forests, provision. beach forests and coastal sand dunes in mitigating the effects of tsunami. The biggest Aceh tsunami on December 2004 is not normal one concerned with the biggest magnitude of 2.3 The formulation of a detailed earthquake. There were in offshore of plan for emergency evacuation western part of Sumatra Island, long of vulnerable coastal distance bottom crust was broken 600 km communities as well as for only one hour. This long distance organizing the evacuation drills motion for long time caused non-linier in order to make the appropriate mechanism for biggest tsunami. It is the response more of an instinctive most important study at moment to make reaction, requiring less thinking clear of dynamical processes of non-linier during an actual emergency tsunami. situation.

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References Rastogi, B.K. and R.K. Jaiswal. 2006. A Anonym. 2006. Final Report on Pilot Catalog Of Tsunamis In The Indian Project by using the ADEOS II Data in Ocean. J. Science of Tsunami Hazards, Indonesia. Denpasar. CRESOS. Vol. 25, No. 3: 128-143. University of Udayana. Satellite image map of Aceh Tsunami . available at www.unosat.org Digital Globe, available at http://www.diaitalglobc.com. tsunami Smith, Walter H.F. el at. 2005. Early galeryhlml Model Estimates Confirmed: Satellite Altimeter Measure Tsunami. J. Janaka J. Wijetunge. 2006. Tsunami On Oceanography, 18: 11-13. 26 December 2004: Spatial Distribution Of Tsunami Height And Thanawood. C. etai. 2006. Effects Of The The Extent Of Inundation In Sri December 2004 Tsunami And Disaster Lanka. J. Science of Tsunami Hazards. Management In Southern Thailand. J. Vol. 24, No. 3: 225-239. Science of Tsunami Hazards, Vol. 24, National Science Foundation (NSF). 2005. No. 3: 206-217. The Great Sumatra Earthquake and Indian Ocean Tsunami of December 26, 2004. Jakarta. EER1 Special Earthquake Report.

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