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 ■ Earthquake Damage in Yogyakarta due to The Central Java Earthquake of May 27, 2006 Preliminary Survey

Ryuzo Ohno Dr. , Professor
Syam Rachma Marcillia ST. , Research Student
Department of Built Environment, Tokyo Institute of Technology

1. Introduction

Earth quake measuring M6.3 struck the Indonesian island of Java with the epicenter of about 20km south of the city of Yogyakarta at 5.53 AM local time on Saturday, 27th May 2006 . Even though the earthquake lasted for only 57 seconds with an afterschock occurring at 10.15 AM , it killed over 5,000 people, injured thousands and made more than 200,000 homeless. This is a preliminary field visit to investigate the damage and to obtain information on how the earthquake affected the life of the people.

2. Field Visit Area

1st day: Bantul Regency (area A): Jl. Parangtristis - Sewon (Information Desk and BPKP) - Patalan (Sewon) - Wonokromo - Pleret (Bawuran) - Imogiri.
2nd day: Klaten Regency (area B): Mlese - Birin - Canan - Pasung ? Gentan - Prambanan.temple.
3rd day: Yogyakarta's City area (area C ): Among Progo Sport Center - Kotagede (Yogyakarta's old town)- Kraton ( Sultan Palace ) - Meeting with JAR (Jogya Arch Quick Response), Gadjah Mada University .

3. Field Surveys for Physical Aspects

3.1 Public Facilities

After the observation, one of the main concern is that public facilities such as government buildings, schools, sport centers, etc., which supposed to be a safe place if such disaster happens, actually have suffered more damages than the others. Most of the damaged parts are found in the roof system, freestanding reinforced concrete columns and beam-column joints. The d amage of structures attributed to failure of design for safety, poor quality and insufficient material used for reinforcement.


Photo. C.1-2: Among Progo Sport Center damaged in the roof system
and cantilever reinforced column on the top floor.


Photo A.1-2: BPKP (Finance and Development Audit Agency) Government building,
damaged in the RC beam-column structures where RC columns lap-sliced at joints.


Photo. C.3 (left) & C.4 (right): Saphir Mall and Gramedia Bookstore,
private owned shopping mall, damages on glass walls.

3.2 Brick Structure vs. Wooden Structure Housing

From the interviews, it was known that most of casualties happened due to the falling of house's parts from heavy debris of brick walls and roof components. In most cases, these structures were brick masonry with weak reinforced (RC) frames and in some cases without any RC columns or beams.


Photo. B.1 (left) and C.5 (right): Houses in Patalan and Kota Gede
with rigid RC frame structure remained while others collapsed.


Photo B.2 (left) and B.3 (right): Un-reinforced Brick House with no RC columns
between the walls is completely collapsed and the brick wall with no beam is directly
connected to the roof system.

What is really interesting is that the survival and rehabilitation of wooden structures in housing. Even though some of the wooden structures used are old, it remains standing while the addition of brick wall is collapsed. Moreover unlike remained brick structure houses that were abandoned, the remained wooden structure (even with slight dislocation) is re-used by its occupants as their primary structure when they renovated their house (A.3&C.6)


Photo A.3 (left) and C.6 (right): Old houses with wood structures,
occupants maintain its old wooden structures with temporary bamboos support for undergoing renovation.


Photo B.4-5: An old house with wood roof system and lightweight wall still exists
while the brick wall additions were collapsed.

3.3 Traditional Structure

From the observation, traditional structure system remained, while newer structure with brick walls collapsed. In such cases, traditional `Joglo` *1 house with its `Saka Guru` *2 structure, lightweight bamboo-net wall or just a cattle or chicken house with `takik` *3 structure system (in Japanese known as `NUKI joint structure system`) remained standing from the earthquake.


Photo B.6-7: An old wood structure with `Takik` structure is the only standing structure remains
in the whole Pleret village.


Photo B. 8 (left): A cattle house with `Takik ` *3 structure system is more flexible
to the shaking force of earthquake.
Photo B.9 (right): Traditional house with light bamboo-net walls remained
because of its lightweight and flexibility.


Photo C. 7-8 : An old House in `Kota Gede ( Old Town ), with `Saka Guru`
*2 structure stands more than 50 years.

4. Field Surveys for Social and Behavioral Aspects

4.1 Survivors Conditions and Activities

Until the time of the visit (around 2 weeks after the earthquake), survivors still live on temporary tents close to their old house/private property. Most of them are low-income people. After the disaster, new groups of vulnerable people emerged; they are youth (orphans) and women (widows and single mother). The physical health of the survivors deteriorated because of inadequate shelter and poor sanitary conditions. Most of these people still lived on the donations and are afraid of the after-shocks that still happen.

The Javanese cultural lifestyle, such as `gotong royong` *4 and `kekeluargaan` *5 , is one of the unique way for the survivors to recover. It is a traditional community system where there is social interaction within the neighborhood to help each other. While the men gathering together with volunteers to clean up the area, the women would gather to make a public kitchen work and public baths use.


Photo. A.4: Temporary guest area, even in their deep sadness of family and house loss,
they still have the Javanese spirit of `Sugeng Rawuh` *6 to welcome others.
Photo. A.5: With `Gotong royong` *4 spirit, youth,
elders and with the help from volunteers clean the damaged area.

The cultural influenced is also reflected on the community's public facilities. The so-called `common field` *7 and `gardu ronda` *8 are some of the facilities they had been using as gathering places of the community for sports, evening gathering, security base, and other events in their village. In the case of May 27 th earthquake, `common field` *7 became temporary emergency areas used as shelters area and evacuation sites, meanwhile `gardu ronda` *8 used as donation and information posts.


Photo A.6: `Common Field ` *7 as community gathering place
Photo A.7: `Gardu Ronda` *8 as community security base.

4.2 Information Issues.

After the earthquake, most of the survivors were left with trauma and confusion. Since education about disaster has never been introduced formally before, they are very fragile to such danger issues, for example several hours after earthquake, rumors about tsunami arise and made chaos in Yogyakarta city, which is around 30km away from the seacoast.

Other issues they are vulnerable too is lack of information about their house structures, for instance, until now there are confusion whether it is safe or not for them to live again inside their damaged house that still stands. For the survivors, this kind of is very important for them to resume their daily activities again. Until the time of this visit, the people only get information from the volunteers, who do not necessarily have the correct information.


Photo.A.8 (left): Mosque as prayer place, gathering place and could be a source of information.
Photo A.9 (right): Information Board for the community.

5. Concluding Remarks and Recommendations

5.1 Physical Aspects

Providing an earthquake resistant structural system that design for safety with good quality materials is necessary for public facilities.

Wood structure not only capable to withstand the shaking of the earthquake but also re-usable as reconstruction/renovation materials either as the primary structure again or addition. From the observation, we can learn from the traditional construction techniques that have certain structural design principles and that give more flexibility and support from certain force such as earthquakes. These principles could be studied and applied to modern construction too.

We noticed that damages between villages in very close area seem to be varying significantly. This might be caused by differences in soil conditions, therefore it need further examination.

5.2 Social and Human Behavior Aspects

a. Survivors Condition and Activities

Physically, the condition of the survivors needs to resume regular health and food service. Community?based works, skills training, and other supports will give temporary incomes and advance the recovery of their daily activities.

The traditional lifestyle and spirit promotions such as `gotong royong` *4, `kekeluargaan` *5 ., will be a valuable program for psychological recovery. Society participation for consultation and socialization through formal or informal institution is important too. This kind of interaction between the survivors and outer civil society will lessen the burden of the trauma and distress effects of the earthquake.

b. Information issues.

The necessity for information system is urgent. Not only to reduce the effects of earthquake but also to educate people how to prevent and cope with future disasters . The information distribution would involve cooperation of government, NGO and local community. It is not only through formal education programs in schools, television, radio and newspaper but also include traditional information system through local gathering communities (teenager `karang taruna`, housewives `arisan`, etc.). Local community facilities such as Mosque, information board, `gardu ronda ` *8 , etc., can also be a place to distribute reliable information through the local community.

Acknowledgement

Financial support from Center for Urban Earthquake Engineering (CUEE), Tokyo Institute of Technology, to undertake this visit to Yogyakarta , is gratefully acknowledged.

This field visit was successfully completed with the help of Mr. Toni and Mr. Wahyu from Gadjah Mada University , who joined the field trip. The discussion with JAR (Jogya Arch Quick Response) staffs especially to Ir. Arif Kusumawanto MT. from Architecture Department, Gadjah Mada University is gratefully acknowledged.

Last but not least, we would like to thank to the survivors for the sincerity in the interviews and extent our deepest condolences for the loss of family member and property in this earthquake.

Notes and Terms

*1. Joglo: One of the traditional Javanese house type.
*2. Saka Guru: Four main columns structure that give supports to the whole roof structure in traditional Javanese `Joglo` house.
*3. Takik: Wood stucture system similar to `NUKI` stucture system in Japan that resist the lateral force and give flexibility in the joints of construction.
*4. Gotong Royong: The spirit of the Javanese people to help each other in good and bad time.
*5. Kekeluargaan: Extending feeling of kinship between Javanese communities.
*6. Sugeng Rawuh: Javanese word of `please welcome to our house` it is the spirit of welcoming and sincerety of Javanese people.
*7. Common Field: An open area/field owned and used by the community as gathering place, sport field and other events.
*8. Gardu Ronda: a basecamp/post owned and organized by the local community as security based.



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