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The 2006 Yogyakarta, Java Earthquake (5/26)

By: Sandy Lieu

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Figure 1: Borobudur Temple in Yogyakarta, Java


Introduction

Yogyakarta is a special region in Java and was a tourist destination. It was known for their Borobudur, an ancient Buddhist stupa north of the earthquake area, and their Hindu temple at Prambanan. (See Figure 1). It was also the center of classical Javanese fine art and culture such as batik (dyed fabric), ballet, drama, gamelan music, poetry, and puppet shadow plays.

Background

The island of Java plays a dominant role in economic and political life in Indonesia. Its population is known to have exceeded 124 million people and is the most densely populated island in the world and the 13th largest island in the world. In addition, the city was known for high education and several major universities. They had a state university called Gadjah Mada University, which was founded in1949, the Hatta Foundation Library, the Sono Budoyo museum, an art academy, and a private university. However, when the 2006 Yogyakarta, Java earthquake hit, it devastated many lives and destroyed many ancient buildings.

The Event

On May 26, 2006, a magnitude 6.3 earthquake hit the central island of Yogyakarta, Java in Indonesia. (See Figure 2). It occurred on Friday, May 26, 2006 at 22:53:58 (UTC) on Coordinated Universal Time and early Saturday, May 27, 2006 at 5:53:58 AM local time at the epicenter when people were still sound asleep in their beds. The earthquake had a duration of 52 seconds, which is a long duration for the magnitude of the event. It occurred near Mt. Merapi, which is an active volcano. (J. M. Nichols). There is research although it is not official, but it is believed that there may be a direct link between the May 26, 2006 earthquake and the Mount Merapi volcano. The Mount Merapi volcano is located several tens of kilometers to the north of the epicenter of the Java earthquake. Having the occurrence of shallow-focused earthquakes located near volcanoes is common world wide. It is almost certain that these shallow-focused earthquakes are triggered by the magmatic processes that are causing the eruotions in the volcanoes. This is thought because the time and space ratios of these earthquakes and volcanic eruptions are so close together. These close spatial associations with the earthquakes and volcanic eruptions is most likely due to both seismic and magmatic phenomena that is localized by a broader tectonic process. Current research is being done to conclude this hypothesis.

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(Figure 2: General Location map and epicenter, Elnashai, Kim).

This type of event is believed to have occurred near a major Subduction area. Furthermore, the tectonics of Java is dominated by the Subduction of the Australia plate north-northeastward beneath the Sunda plate with a relative velocity of about 6 centimeters a year. (USGS). The Australia plate dips north-northeastward from the Java trench. (USGS). Additionally, the interaction of the two plates below the surface of the Earth caused this earthquake. The result of the aftershock observation is an area that involves a left-lateral strike-slip motion with a location 10 km east of Opak Fault. (Lucas Donny Setijadji 2). Many researchers believe that the Opak fault, which is located at the eastern boundary of Yogyakarta low-land area and the high-land region of Southern Mountains, was the source of the year 2006 earthquakes. (Setijadji).

Damage and Casualties

Java is a high-populated island due to their prosperous region. It is the center of major education resources, which include universities, secondary schools, and primary schools. More than 5,700 souls were taken at that point and at least 38,568 people were injured and as many as 600,000 people were displaced in the Bantul-Yogyakarta area. In addition, there were more than 127,000 houses destroyed and an additional 451,000 were damaged in the area. The types of buildings that were mainly destroyed consisted of non-engineered buildings, meaning that people who were not qualified in a branch of professional engineering built it. The houses were usually one or two stories high, which either collapsed or were brutally damaged because the walls of the houses were very weak. (See Figure 3). In many cases wall thickness was not adequate or the reinforcing beams and columns were also too slim and therefore insufficient. (Guosheng, QU). In addition to the wall thickness, the building material quality was not sufficient to withstand earthquakes of any substantial magnitude, as they were made of mostly bricks and tiles. (Guosheng, QU). When they collapse, they tend to tear apart at the same time because the houses were connecting using lime and sand mixture often without mortar. In cases where mortar was used, collapse was still seen because the mortar bond between bricks was not strong enough. (Guosheng, QU). This led to many deaths and injuries when buildings and walls collapsed. The damages of infrastructures such as roads, bridges and irrigation facilities were not heavy by comparison with the damages of brick-built housings. (Iizuka Atsushi). In figure 4, the house consisted of one (one and half) brick thick masonry without reinforcement or half a brick thick masonry with and without reinforcement. (Teddy Boen 3). Their rooftop was a timber roof system, which contained slate, metal asbestos-cement or plastic corrugated tiles on their roof. (Elnashai, Kim 25). There was no support between the roof and masonry walls; also, roofs were often excessively thick of heavy causing them to collapse. (Guosheng, QU). Along with the problems caused by how buildings were structured, collapse of buildings was due to the fact that they were built on an alluvial plain in front of mountains, which was shown to be more damage prone. (Guosheng, QU). In these plain areas, the population is extremely dense and as a result, there are many casualties in a relatively small area. (Guosheng, QU). Finally, the earthquake occurred early morning on a weekend and because many people were still sleeping at this time, they were trapped or injured by sudden collapse on top of them. (Guosheng, QU). As a result, the estimated total cost of loss was approximately 3.1 billion U.S dollars.


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(Figure 3: Heavily Damaged Building, Elnashai, Kim).



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(Figure 4: One (One and Half) Brick Thick Masonry in Bantul, Boen).

Moreover, people were sick with skin diseases because of the poor sanitation. Many people were left homeless and were living off plastic tarps. There were no toilets or running water. The water for washing was from the wells and streams in many villages and eventually became polluted because of the poor sanitary conditions mixed with rainwater. In addition, many patients were not taking proper care of their wounds when they got treated.

Temple Damage

Yogyakarta is the known to be a former Javanese royal capital and home to historic temples and palaces. During the earthquake, the renowned Prambanan Hindu temple was sent crashing to the ground, which undid years of restoration. (See Figure 5 & 6). The reason for this was due to the fact that it was much more closer to the epicenter. However, the 7th Century Borobudur Buddhist temple survived intact. (See Figure 7).

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(Figure 5: Before Picture of Prambanan Hindu Temple).


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(Figure 6: After Picture of Prambanan Hindu Temple).
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(Figure 7: Borobudur Temple).



Recovery

The first priority in this kind of disaster is medicine and clean water. Everything has to be done as quickly as possible and efficiently. For example, getting injured people to hospitals is a must and supplying people without homes a tent and food. In addition, the results of the earthquake led to many international aids, one of them being the United States. U.S. Marines joined an international effort to deliver aid and medical equipment to some 200,000 Indonesians left homeless by a devastating earthquake, as hopes faded of finding more survivors. (En-Lai Yeoh). Furthermore, most survivors that were still living in improvised shacks or group shelters erected in rice fields. Groups of families cooked together, each contributing scavenged food. (Yeoh).

Conclusion

The May 26, 2006 Yogyakarta, Java Earthquake is one of the biggest disasters in human history. It has taken and destroyed many innocent lives and took many houses with it. Although this has only happened about one and a half years ago, recovery will definitely take some time. In the mean time, many people from all over the world have joined together to help this city. The city will eventually come to a satisfied recovery from the lessons learned and play a dominant role in the economic and political life of Indonesia once again.

References:

1. Atsushi, Iizuka. “Report of Java Earthquake Disaster on May 27, 2006”
<http://sciencelinks.jp/jeast/article/200621/000020062106A0837275.php>
2. Boen, Teddy. “Yogya Earthquake 27 May 2006, Structural Damage Report.” Senior Advisor WSSI (World Safety Initiative) 2006.
3. Elnashai, Amr S., Kim, Sung Jig. “The Yogyakarta Earthquake of May 27, 2006). Mid-America Earthquake Center. Headquarters: University of Illinois at Urbana-Champaign. MAE Center Report No. 07-02.
4. Nichols, J. M. “The 2006 Yogyakarta earthquake – a preliminary study of deaths” Transactions of the Wessex Institute.
<http://library.witpress.com/pages/PaperInfo.asp?PaperID=17700>
5. Setijadji, Lucas Donny. “Geology of Yogyakarta earthquakes 2006 (central Java, Indonesia): Current Understanding based on integration of research outputs in geology, geophysics and remote sensing.” Geophysical Research Abstract, Vol. 9, 06767, 2007.
6. Setijadji, Lucas Donny. “Interpretations on the Geologic Setting of Yogyakarta Earthquakes 2006 (Central Java, Indonesia) Based on Integration of Aftershock Monitoring and Existing Geologic, Geophysical and Remote Sensing Data.”
<http://www.agu.org/cgibin/SFgate/SFgate?&listenv=table&multiple=1&range=1&directget=1&application=sm07&database=%2Fdata%2Fepubs%2Fwais%2Findexes%2Fsm07%2Fsm07&maxhits=200&=%22S31C-01%22>
7. Magnitude 6.3 – Java, Indonesia. USGS Earthquake Hazards Program.
<http://earthquake.usgs.gov/eqcenter/recenteqsww/Quakes/usneb6.php>
8. Yeoh, En-Lai. “U.S. Military Joins Indonesia Quake Relief.” CBS News. May. 31, 2006.
<http://www.cbsnews.com/stories/2006/05/31/ap/world/mainD8HUGLJO0.shtml>.
9. Guosheng, QU. “Earthquake Disaster Assessment on May 27 Ms 6.2 Yogyakarta Earthquake of Indonesia”. Codata. October 23rd, 2006. http://www.codata.org/06conf/presentations/C4/QuGuosheng.pdf
10. http://earthquake.usgs.gov/eqcenter/recenteqsww/Quakes/usneb6.php