Indonesia

DECEMBER 26, 2004 INDIAN OCEAN TSUNAMI
FIELD SURVEY (JAN. 21-31, 2005) AT NORTH OF SUMATRA ISLAND

The full report can be downloaded in PDF form HERE (4.35 MB)

You can also visit the http://yalciner.ce.metu.edu.tr/sumatra/survey/

Ahmet C. Yalciner1 , Dogan Perincek2 , Sukru Ersoy2, Gegar S. Presateya3,
Rahman Hidayat3, Brian McAdoo4
March 08, 2005

1 Middle East Technical University, Civil Engineering Department, Ocean Engineering
Reserach Center, Ankara, Turkey yalciner@metu.edu.tr
2 Yildiz Technical University, Natural Sciences Research Center, Ocean Engineering
Research Center, İstanbul, Turkey ersoys@yildiz.edu.tr and perincek@yildiz.edu.tr
3 Coastal Dynamic Research Center Agency for The Assessment of Application Technology
(BPP Teknologi), Jl. Grafika No.2, Yogyakarta 55281, Indonesia, gegar@lycos.com
4 Visiting Professor Institute of Geology, ETH Zentrum, CH-8092 Zurich, Switzerland (On leave from Vassar College until July 2005) brmcadoo@vassar.

SUMMARY
This report is about the the field survey performed in between January 21-31, 2005 at North Coast of Sumatra Island at Medan, Meulaboh cities and Simeulue Island. In the report we presented the survey results about runup, arrival time and damages of tsunami. Additionally we also presented the prelinminary results simulation performed by Yalciner in comparison with the survey results of other tsunami survey teams at Sumatra, Thailand, Sri Lanka, India and Maldives.

1. INTRODUCTION
International Tsunami Survey Team consisted of Ahmet C. Yalciner (Turkey), Dogan Perincek (Turkey), Sukru Ersoy (Turkey), Gegar S. Presateya (Indonesia), Rahman Hidayat (Indonesia), Brian McAdoo (USA) have performed the field survey in between January 21-31, 2005 along coasts of Medan, Meulaboh cities, and Simeulue island which are located North of Sumatera with the invaluable survey support by UNESCO IOC and also invaluable logistic and administrative supports by Indonesian Government, Ministry of Fisheries and Marine Affairs, and Indonesian Army. The Russian survey team Victor Kaistrenko (leader) and Nadia, Yuri, Andrey Zaitsev, Nocholai Poloukhin has participated and contributed the survey in Simeulue island and Medan.
In theis report we presented our survey results on runup, arrival time and damages of tsunami at North of Sumatra. Additionally we also presented the prelinminary results of simulation performed by Yalciner in comparison with the survey results of other tsunami survey teams at Sumatra, Thailand, Sri Lanka, India and Maldives.

2. INDONESIA / NICOBAR / ANDAMAN / SUMATRA EARTHQUAKE ON DECEMBER 26, 2004

 The devastating megathrust earthquake ( Indonesia/Nicobar/Andaman/Sumatra Earthquake) of December 26, 2004, occured on Sunday, December 26, 2004 at 00:58:53 GMT (7:58:53 AM local time at epicenter) with Mw=9.0 NEIC Epicenter Latitude 3.32 North, Longitude 95.85 East (USGS) or 3.09N, 94.26E southwest Banda Aceh in Northern Sumatra (Borrero, 2005). The earhquake occurred on the interface of the India and Burma plates and was caused by the release of stresses that develop as the India plate subducts beneath the overriding Burma plate. The India plate begins its descent into the mantle at the Sunda trench, which lies to the west of the earthquake's epicenter. The trench is the surface expression of the plate interface between the Australia and India plates, situated to the southwest of the trench, and the Burma and Sunda plates, situated to the northeast (Taymaz,Tan, Yolsal, 2005). The fault plane solutions of the earthquake are shown in Figure 1.

Figure 1. The fault plane solutions of December 26, 2004 Earthquake (Taymaz,Tan, Yolsal, 2005).

3. INDIAN OCEAN TSUNAMI ON DECEMBER 26, 2004

The earthquake has also triggered giant tsunami and the tsunami waves that propagated throughout the Indian Ocean and have caused extrme inundation and extensive damage, loss of property and life along the coasts of 12 surrounding counties in the Indian Ocean. The loss of lives has also been extended to the people from totally 27 countries from other parts of the world. The number of casualties and missing from the Countries Bordering Indian Ocean, (AFP, 2005) given in Table 1.

The tsunami waves have arrived North of Sumatra in half an hour. The waves have arrived Thailand and Sri Lanka, India and Maldives within hours and also arrived Somalia Africa some hours later. The number of casualties and missing people are listed in Table 1 (AFP, 2005). The total number of death toll in the list shows that this tsunami is the first one of the most destructive tsunamis experienced in human life from antiquity. Because of this exceptional character, it is clearly seen that, the shaking of North Sumatra Earthquake has not only triggered a tsunami and cause damages and loss of lives but also shaked the psychology, social life, scientific considerations, understanding of hazards and priorities of mitigation measures. This event will remain as the most important item in the agenda of assessment of natural hazards in the long run.

Table 1. The number of casualties and missing from the Countries Bordering Indian Ocean (AFP, 2005)

Understanding of Indian Ocean Tsunami will provide us very valuable experience, knowledge and sense to develop better defense of humanity against natural hazards. In the following the tsunami survey performed by ITST (Turkish, Indonesian, Russian, USA) is described briefly and the results are presented.

4. TSUNAMI FIELD SURVEY AT NORTH OF SUMATRA ON JANUARY 21-31, 2005

 International Tsunami Survey Team consisted of Ahmet C. Yalciner (Turkey), Dogan Perincek (Turkey), Sukru Ersoy (Turkey), Gegar S. Presateya (Indonesia), Rahman Hidayat (Indonesia), Brian McAdoo (USA) have performed the field survey in between January 21-31, 2005 along coasts of Medan, Meulaboh cities, and Simeulue island which are located North of Sumatera with the invaluable survey support by UNESCO IOC and also invaluable logistic and administrative supports by Indonesian Government, Ministry of Fisheries and Marine Affairs, and Indonesian Army. The Russian survey team Victor Kaistrenko (leader) and Nadia, Yuri, Andrey Zaitsev, Nocholai Poloukhin has participated and contributed the survey in Simeulue island and Medan.

The survey locations are tabulated in Table 3 and and shown on the Figure 6-7. The water level data in Table 2 are before tidal correction. For tidal correction the data is given in Tsuji, Namegaya and Ito, (2005).

Table 2: The list of measured parameters by the Turkish-Indonesian-USA Team during the field survey on Sumatra on January 21-29, 2005. (The water level data are before tidal correction)

Figure 2. The survey locations on the Map of North Sumatra

Figure 3. The survey locations on the Map of North Sumatra

4.1. FIELD SURVEY NEAR MEDAN COAST

 The field survey has been performed on January 21, 2005 at the coastal regions named Pantai Cermin and Kuala Ruteri near Medan. Tsunami waves have also been arrived in these localities after diffraction from the north part of Sumatra island. The survey near Medan coast provided us the data for understanding the transformation (shoaling, diffraction and refraction) characteristics of tsunami waves. According to our eyewitness interviews at two survey sites, it was determined that

• The arrival time of tsunami waves was about 4 hours, and
• The maximum elevation of the water level near the coastline has exceeded 2-2.5m elevation (as measured from the traces on the walls of houses). The sediment deposited irregularly on land near the coastline depending on the land topography near the shore. The inundation distance was observed as about less than 1 km at survey points at east of Medan.

Figure 4. The Survey Location near East of Medan

4.2. FIELD SURVEY ALONG THE COAST OF SIMEULUE ISLAND

 The survey has been performed on January 22-26, 2005 at the coastal regions named. Laubang, Lantik, Tembah Barat, Salur, Busung, Labuhan Bakti, Belawan Port, Ganting, Sinabang Port, Senebu, Tanjun Raya by ITST, and additionally near Alafan at North of Simeulue (by Russian team). Simeulue island provides very illustrative picture of understanding, awareness and mitigation of tsunami hazards. The previous experience of tsunami attack to west side of this island in 1907 have thaught the peolpe that the sea inundation (called “smong” in local language) may cause damages, loss of life and property near the coastlines. The people always were very sensitive about the sea motion after erathquakes since 1907 event. It was noted by the Governor of the Island (Buphati Dr. Darmili) that all people had escaped from the shoreline when they felt earthquake and 8 people died out of 78 000 inhabitant in the island. The hardest tsunami hit was reported at north of island near Alafan (maximum tsunami elevation was more than 10 m). The most damage was at Labuhan Bakti at south of island where the maximum tsunami elevation was more than 2.5 m. According to our eyewitness interviews at the survey sites near Simeulue, it was determined that

Sea receded in 10 minutes after the earthquake about 200-400 m and at about 30th minute after the eq. the first wave has arrived, and second one folowed it 50-60 minutes after the first one, and The maximum elevation of the water level near the coastline has exceeded 3 m elevation (as measured on the walls of houses.

Figure 5. The survey locations at Simeulue Island

4.3. FIELD SURVEY ALONG THE MEULABOH COAST

 Tsunami has directly attacked towards north west coast of Sumatra Island from 25 km south of Meulaboh to north tip of the island Banda Aceh. The tsunami inundation started from the coastal location at 30 km south of Meulaboh city. The inundation distance is observed as about 5 km and almost the same along the south and north coast of Meulaboh city. The wave propagated much more distances towards inland along the rivers’ beds.

It was determined that tsunami waves have exceeded the height of coconut trees along Meulaboh coasts, have inundated 5 kilometers towards land, and have totally destroyed the Port of Meulaboh and its surrounding area, and have also killed about 2/3 of the whole population in Meulaboh. It was also determined that the loss of life has reached 70 percent of the population in Tanom and Calang cities at the north of Meulaboh coasts

According to our eyewitness interviews at all survey sites near Meulaboh, it was clearly determined that

• Sea receded in 10 minutes after the erathquake about 500 m and advanced with the amplitude of 1-1.5. At about 30 minute later, the second wave, but the first desctructive wave has arrived, and second destructive wave arived 50-60 minutes after the first one, and
• The maximum elevation of the water level near the coastline has exceeded 15m elevation (in comparison with the height of coconut trees) during either the first and second destructive waves. Totally 5 main coastal areas have been surveyed on land at south and north of Meulaboh. The inundation distance is clearly distinguished by the dried vegetation along the coastlines because of the salt water inundation.

The southern end of tsunami attack (where the inundation distance is short) at north west coast of Sumatra island has also been documented by a series of air photographs (southernmost survey point on the map shown in Figure 10). There was no safe access along the road to Calang because of damages on amost all the bridges in the inundation zone of tsunami. The increasing pattern of inundation distances and higher runup elevations will be measured when the field survey is extended to far north of Meulaboh to Tanom, Calang and Banda Aceh.cities when the bridges and road are repaired for transportation.

Figure 6. The survey locations near Meulaboh

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