EARTHQUAKE DISASTER OF AND CENTRAL , AND DISASTER REDUCTION,

Sutikno Faculty of Geography, Gadjah Mada University, Yogyakarta, Indonesia Research Centre for Disaster, Gadjah Mada University, Yogyakarta, Indonesia E-mail: [email protected]

ABSTRACT This paper discussed on earthquake disaster and its reduction of Yogyakarta and , Indonesia. The study area is located at relatively a short distance from subduction zone of India-Australian and Eurasian plates. Geologically this area is characterized by fault and graben structure, and geomorphologically is composed of block mountain, karsts topography and fluvio-volcanic plain. Aim of this paper is to evaluate the spatial distribution of the damage area, the environmental impacts, and to discuss the risk reduction of earthquake disaster scientifically and practically. In this paper to determine the hazard susceptibility zone and their environmental impact used geologic, geomorphologic, land use map, remote sensing image interpretation, and field observation. Discussion on the earthquake disaster risk reduction based on the hazard susceptibility and the characteristic of the human settlement and facilities. The result of this study shows that: i).the high damage area associate with distribution of the fault structures and the lithology; ii). mass-movement, lowering of groundwater, rising new springs, liquefaction, cracking of rocks and land surface; iii). structural non structural efforts are used for earthquake disaster reduction.

Keywords: earthquake disaster, environmental impact, structural and non structural effort for reduction

INTRODUCTION become active tectonic and active volca- nic as well. The active tectonic related to Last three years Indonesia was hit by some hazard or disasters such as earth- several types of disasters, such as: earth- quake, tsunami, fault, uplift, subsidence quake in Aceh (2004), Nias (2005), Yogya- and mass-movement. While the active vol- karta, Central Java, and (2006); canic region associated with some type of volcanic eruption in Yogyakarta (2006); hazards or disasters such as: volcanic erup- flood in Java, Kalimantan, Sumatra, Sula- tion, pyroclastic rain, nue ardente, lahars wesi (2004, 2005, 2006); hot mud in East flow and toxic gas, there are for about 129 Java (2006); mass-movement (landslides) active volcanoes in Indonesia. The Merapi in Java, Sumatra, Sulawesi (2004, 2005, which is located in the northern part of 2006). There are some geographical situa- Yogyakarta is the most active volcano in tions that influence why Indonesia region Indonesia. The effects of the location in is susceptible to many type of disasters, between two oceans and two continents, because the location is: in collide of three Indonesia has wet tropical climate. It asso- huge plate tectonics (Eurasian, India-Aus- ciates with active exogenous processes, tralian and Pacific plates), between two which may cause flood, mass-movement oceans (Pacific and Indian), and between (landslides), erosion, drought and fire. It can two big continents (Australian and Asian). simply state that Indonesia is very rich in The effects of the collide plates, the region disaster (Sutikno, 2006).

Earthquake Disaster of Yogyakarta and Central Java ... (Sutikno) 1 th Earthquake on 27 May 2006 has of Yogyakarta and its surrounding was very devastated southern part of Yogyakarta crowded. People from the northern part Special Region and east-southern part of went to the south because afraid from Central Java Province. The Yogyakarta Merapi eruption, and reversely because Special Region is a province that consists afraid of tsunami; some traffic accidents ththth of five districts: Bantul, Yogyakarta, Sle- occurred and it caused injury and death. th man, Gunungkidul and Kulon Progo. Earthquake disaster on 27 May 2006 with Among those districts the most damage magnitude 5.9 SR (BMG) or 6.3 (USGS) areas are Bantul , southern part of Sleman, caused large number of victims, houses and southern part of Yogyakarta municipality public facilities damage. Actually the and western part of Klaten district ( it be- magnitude of the earthquake is in medium long to Central Java Province). Yogyakarta scale, but it is not comparable with the Special Region and Central Java Province number of the victims and the loss of is located in Java Island. The Java Island is properties. This condition invites a question a part of Indonesia territory among 17.508 and interest to discuss. There are three islands. Most of the islands are character- problems will be discussed here: i).why the ized by tectonic and volcanic activity, and study area has a high susceptibility to humid tropic climate. That is why most part earthquake disaster and high vulnerability; of Indonesia is prone to so many types of ii). what is the environmental impact of natural disaster, such as flood, drought, earthquake disaster; iii). what kinds of landslide, earthquake, volcanic eruption, reduction program to anticipate the and tsunami. The tectonic and volcanic probable disaster in future? activities in Indonesia are caused by the location in the collision of three huge plate DATA AND METHOD tectonics: India-Australia, Pacific and Eurasia. The study area is located in the The earthquake in Yogyakarta and collision between India-Australian and Central Java was caused by tectonic activ- Eurasian plate (Fig. 1). ity, and was triggered by disturbing of the subduction zone between India-Australian th When the 27 May 2006’s earth- and Eurasian plates. Relating to tectonic quake occurred, it was accompanied by type’s of earthquake, geological, geomor- thundering sound, most people of phological, hydrological data are needed to Yogyakarta supposed that the thundering evaluate the disaster susceptibility, while sound come from the Merapi volcano erup- land use data are needed for damage as- tion ( it is located in the northern part of sessment. Geological, geomorphological Yogyakarta), because at that period the and hydrological data are obtained by map Merapi volcano was erupting. Fifteen min- and remote sensing interpretation (manu- utes after the thundering sound, the real ally) and field observation. The existing event was known as earthquake that epi- geological map in scale 1: 100,000 scale and center is located in the southern part of Landsat TM in 1:250.000 scale was used Yogyakarta, precisely near by the mouth of to identify the lithology, the geological Opak River. There was tsunami issue at that structure and landform condition that pro- th time as occurred in Aceh on 27 Decem- mote the earthquake disaster. The existing ber 2004, by the issue the traffic condition topographic map in 1:50,000 scale and

2 Forum Geografi, Vol. 21, No. 1, Juli 2007: 1 - 16 IKONOS bird images before and after parts: east, middle and western parts. Bound- earthquake were used to identify of land ary between the middle part and eastern is use type and to evaluate the damages. Field Opak River, while the middle and western observation on purposive framework was part bordered by . Each parts has carried out to determine the actual dam- specific in lithology, geological structure and ages and to estimate the environment im- geomorphological condition, as follow. pact on the physical aspect. Based on the bio-geophysical, the actual damage, the Geology and Geomorphology of the land use types data, the geographical loca- Eastern Part tion of the study area, and integrate to the local government program an idea to re- Structurally the eastern part is block duce for the disaster in future is formulated. hilly to mountainous area; in the west side bordered by major Opak fault in SE direc- Geology and Geomorphology of tion; in northern part bordered by Batuar- Yogyakarta and Its Surrounding agung fault in EW direction. Some minor faults occur in EW-SW direction (Fig. 2). In global scale Yogyakarta and its The fault pattern in eastern part associated surrounding are located on the Sunda with the spatial distribution of the damage Mountainous System, which is character- area due the earthquake disaster. The dam- ized by non-volcanic arc and volcanic arc age area beside associated with the fault (Verstappen, 2001). The Sunda Mountain- structure are also influenced by the lithol- ous system is extension of the Eurasian ogy. The lithology of the eastern part com- plate; it is bounded to the Indian-Austra- posed of six unit/formations: alluvium, lian plate. The margin of the plates are in Wonosari, Kepek, Sambipitu, Nglanggran collision, resulting in the consumption of and Semilir formation: plates along subduction zone, the creation of volcanic arcs and compression of ob- 1) Alluvium: composed of sand, loam and lique slip structure (Darman and Hasan clay as weathering and erosion product Sidi, 2000). The collision of the plates and from the existing rock formation; the the subduction zone become a concentra- topography is flat to gently and the land- tion of seismic activity and tectonic activ- form unit is alluvial plain and foot slope. ity as well (Summerfield, 1991; McGeary, et al., 2004; Abbott, 2004). Due to 2) Wonosari formation (Miocene): com- Yogyakarta and it surrounding are located posed of reef limestone, calcarenite and near by the collision of the Eurasian and tuffaceous calcarenite; it forms karsts Indo-Australian plates, geological and geo- topography which is characterized by morphologic condition of the area is char- conical hills, doline, underground acterized by tectonic origin. The geologic stream and caves; due to the large num- and geomorphologic condition of the study ber of the conical hill it is known as area shortly is described below. Gunungsewu (thousand mountains). The structure is plateau and the dip for o Based on the geological condition, the about 8 to the South. (to India Ocean), study area can be distinguished into three and the altitude 0- 450 m msl.

Earthquake Disaster of Yogyakarta and Central Java ... (Sutikno) 3 3) Kepek formation (Miocene): composed posed of alluvium, young volcanic prod- of marl and bedded limestone; the to- uct and Sentolo formation (Wartono pography is undulating and the struc- Rahardjo et al., 1995). The alluvium con- ture is syncline; the landform unit is sist of sand on coastal sand dune, and sand- undulating syncline topography. loam of the back swamp landform unit. The back swamp formed in between natu- 4) Sambipitu formation (Miocene): com- ral levee of Opak river in west side, hilly posed of tuff, shale, sandstone and con- area in eastern side and sand dune in the 0 glomerate; dip of the layer 8 locally in southern side. The young volcanic product NE direction; topography is hilly. composed of sand to loamy sand as prod- uct of the Merapi volcano. Geomorphologi- 5) Nglanggran formation (Miocene): com- cally the young volcanic product is located posed of volcanic breccia, flow brec- on volcanic foot plain and fluvio volcanic cia, agglomerate, lava and tuff; the to- foot plain. The Sentolo (Miocene) forma- pography is hilly with steep slope, the tion consist of limestone and marly sand- altitude in between 200 – 500 m msl. stone. Comparing with the limestone of the Wonosari formation, the karsts topography 6) Semilir formation (Miocene): composed in the Sentolo formation is less develop. th of interbedded tuff breccia, pumice, Relating to the 27 May 2006’s earthquake dacite tuff and andesite tuffs and tuf- disaster the most damages area in the 0 faceous claystone; dip of layer 14-22 middle parts was on the volcanic foot plain and the strike mainly to NE and some and the fluvio-volcanic foot plain. The rea- minor fault occur in EW and NE direc- son is the material composition of the tion ; the topography mostly is hilly, the middle parts is unconsolidated material, the altitude mostly less than 200 m msl. groundwater at shallow depth and the area (Wartono Rahardjo et al., 1995). is near by the earthquake epicenter .

Among those lithological/formation Geology and Geomorphology of the th units that much were influenced by the 27 Western Part May 2006’s earthquake were alluvium, Semilir, Nglanggran, and Wonosari forma- Structurally the western part as tion. It was caused by the characteristic of whole is dome like mountainous, with ra- the rocks properties, the geological struc- dial fault pattern, it is known as West Progo ture, the distant from the fault and the dis- Mountain. The lithology/formation of the tant from the epicenter of the earthquake. West Progo Mountain consist of alluvium, Sentolo formation (Miocene), Jonggrangan Geology and Geomorphology of the formation (Miocene), Kebobutak forma- Middle Part tion (Miocene), Nanggulangan formation (Eocene) and Andesite (Wartono Rahardjo Structurally the middle part is graben et al., 1995). The alluvium consist of two and it is called by Bantul graben. East side types the first is sand from beach ridges, of the graben is bordered by Opak fault and the second sand to clay from alluvial and the west side is bordered by Progo plain and back-swamp. The Sentolo forma- fault. Lithology of the middle part com- tion composed of limestone and marly

4 Forum Geografi, Vol. 21, No. 1, Juli 2007: 1 - 16 sandstone., and Jonggrangan formation study area can be distinguished into: rice composed of conglomerate, tuffaceous field, dry agricultural land, settlement, for- marl and calcareous sandstone with inter- est, plantation and bare land. Spatial dis- calation by lignite seams, limestone and tribution of the land use types do not sepa- corraline limestone. Kart topography in the rate sharply into certain zone, but uneven Jonggrangan limestone is more well develop distributed. The rice fields dominantly are compare to the Sentolo limestone. The distributed on volcanic foot plain, fluvio- Kebobutak formation composed of andes- volcanic foot plain and alluvial plain units ite breccia, tuff, lapilli tuff, agglomerate and of the middle part, while the dry land, plan- intercalation by lava flows. Andesite is lo- tation and forest are distributed on hilly- cated in the centre of West Progo Moun- mountainous units of the eastern and west- tain and together with the Kebobutak for- ern part. mation supposed to be product of old vol- cano (Tertiary). The oldest formation in the The settlements are distributed on western part is Nanggulan that composed various landform units, and especially on of sandstone with intercalated by lignite, volcanic foot plain, fluvio-volcanic foot sandy marl, claystone with limonite con- plain and alluvial plain unit. Based on the cretion, intercalations of marl and lime- function and the facilities, the settlement stone, sandstone and tuff. can be distinguished into urban, peri-urban and rural area. In the study area that hit by Based on the geological and geomor- the earthquake there are two main urban phological condition, the study area has areas, namely Yogyakarta and Bantul. The dynamic development. It means that tec- peri-urban area is located between urban tonic and volcanic activities has been oc- area and rural areas. Accessibility between curred several time in the study area. The urban, peri-urban and rural areas is good, major fault of Opak and Progo and the as- that is why the study area has high popula- sociated minor fault, uplifting of marine tion density. In general most part of the deposits such as limestone of the Wonosari, houses in the peri-urban and rural areas are Sentolo and Jonggrangan formations must old, simple building, one floor, without be caused by tectonic activity and accom- good concrete and tile roof. The such types panied by earthquake. Naturally the study of the houses have high vulnerability to area are prone to earthquake disaster, due earthquake. to the local people and the local govern- ment do not aware yet about the condition RESULT AND DISCUSSION the toll by the last earthquake is too high compare to the magnitude of the earth- Historical Information of Earthquake quake. Death from earthquakes are mostly Disaster due to building failures, and earthquake do not kill, but building do (Abbott, 2004). Historically Yogyakarta area and its surrounding has been occupied for along time th Land use Type before the 7 century. It proved by the ex- isting of the ancient archaeological sites (272 Based on the Landsat TM and sites) of Hinduism-Buddhism period which IKONOS images the land use types in the were found in the area between two main

Earthquake Disaster of Yogyakarta and Central Java ... (Sutikno) 5 rivers in Yogyakarta, e.g. Progo river in the center is 33 km and located near by the west site and Opak river in the east. Most mouth of the Opak river (Fig. 3), at 9.78 S artifacts of the archaeological sites are dam- and 110. 32 E (UTC). age, due to volcanic activities if are located in the volcanic area, and caused by earth- The magnitude of the earthquake in quake if are located at block faulting hilly the study area is classified as medium scale. area. Some of the artifacts were found few The magnitude of earthquake usually cor- meters below the land surface such as relate with the length of shaking, if the Sambisari temple in Kalasan. The ruins magnitude 5- 5.9 RS the duration of strong temple of Candi Boko at Baturagung range ground shaking is 2-15 seconds, and the that located along Opak fault could be magnitude is 6-6.9 RS the duration 10-30 caused by earthquake. The information seconds (Abbott, 2004). above shows that Yogyakarta area and its surrounding several times have experiences The duration of strong shaking of the hit by natural disasters (Sutikno, 2006). Yogyakarta’s earthquake rather exception because the duration took time for about Natural disaster in certain area usu- 55 seconds. After shock, there were many ally has recurrent interval, even with dif- accompanied earthquake or ground shak- ferent in the magnitude and intensity. As ing occurred. Based on the recording data have been occurred in southern part of from BMG after shock of the main earth- Yogyakarta (in Bantul) earthquake in the quake, the frequency of the accompanying year of 1876 devastated 372 houses and 5 earthquakes at the same day was still large persons died; in 1943 there were 2.800 enough, and tend to decrease for the next houses damaged and 213 persons died day even for the next month (Table 1). The (Sutikno, 2006) magnitude of the accompanying earth- quakes mostly less than 2,9 RS at the depth th th Earthquake on the 27 May 2006 10 km. At May 27 , 2006, after shock there were 110 ground shaking that consisted of Most earthquakes are caused by fault : 90 times at <2,9 RS; 18 times at 3-3,9 RS movement associated with tectonic plates, and 2 times at 4-4,9 RS. In June 2006, the the largest number of great earthquake oc- accompanying earthquakes still occurred, curred in the subduction zone of the colli- but the frequency decreased; there were 60 sion of tectonic plates (Abbott, 2004; times that consisted of 49 at < 2.9 RS; 9 at th th McGeary et al., 2004). The case of the 27 3-3.9 RS and 2 at 4-4.9 RS. From May 27 May, 2006’s earthquake in Yogyakarta and until the end of June 2006, there were 170 Central Java are also caused by fault move- accompanying earthquake, and fore about ment that triggered by energy from the sub- 74 % occurred at 10 km depth. The epi- duction zone between Eurasian and Indo- center of the accompanying earthquakes are Australian plates. The magnitude of the located around the main earthquake at the earthquake is 5.9 Richter Scale (RS) accord- range of 110,03 – 110, 59 E and 7,3- 8,33 ing to BMG ( Geophysical and Meteoro- S. Relating to the accompanying earth- logical Agency of Indonesia) and 6.3 Rich- quakes there were evens that un sufficiently ter Scale according to USGS (United Stated explanation; before accompanying earth- Geological Survey), the depth of the epi- quakes occurred always started or begun

6 Forum Geografi, Vol. 21, No. 1, Juli 2007: 1 - 16 Table 1. Accompanying Earthquakes after Shock of May 27th, 2006

Magnitude and the depth of epicenter of the accompanying earthquakes Month Magnitude : < 2.9 Magnitude: 3-3,9 Magnitude: 4-4,9 Magnitude: 5-5,9 and date 10 20 30 10 20 30 10 20 30 10 20 30 km km km km km km km km km km km km May, 27th 49 3 3 7 2 6 1 1 0 0 0 1 May,28th 6 1 5 1 0 0 0 0 0 0 0 0 May,29th 10 1 0 2 0 0 0 0 0 0 0 0 May,30rd 7 1 0 0 0 0 0 0 0 0 0 0 May,31st 2 1 1 0 0 0 0 0 0 0 0 0 Total 74 7 9 10 2 6 1 1 0 0 0 1 May June, 45 2 2 6 0 3 1 0 1 0 0 0 20006

Data analysis of BMG record, 2006 with look like boom sound, after the sound manent displacement of the land surface then followed by shaking. The sound heard (McGeary et al., 2004), and tsunami if the by people who live at the surrounding epicenter is located in the ocean/floor with faulted area. medium to high magnitude of the earth- quake. The intensity impact of the earth- Based on the large number of the quake depends on several variables, such accompanying earthquakes after shock it as magnitude, distance from the hypo- means that the area is still in labile condi- center/epicenter, types of rocks or sedi- tion. It is caused by the existence of the ment making up the ground surface, build- Opak fault and the accompanying faults. ing stile, design, kind of building material The faults were reactivated by the earth- and height, and duration of the shaking th quake on May 27 , 2006. Due the location (Abbott,2004). Regarding to the geologic of the Opak fault near by and faced to the and geomorphologic condition, land use collision of the tectonic plates and the type, building characteristics, the magni- study area above the subduction zone, the tude and duration of the earthquake some reactivated fault will occur in future. The impacts of the earthquake of Yogyakarta study area still has high susceptibility to and Central Java can be identified, such as: earthquake hazard and its associated im- building and houses damages, infrastruc- pact. ture damages, liquefaction, landslide and displacement of the land surface. Impact of the Earthquake of Yogya- karta and Central Java Damage of Houses, Buildings, and Fa- cilities Ground motion or land shaking by earthquakes have some kind of impacts, Due to the long shaking duration of such as damage of building and infrastruc- the main earthquake (55 seconds) on 5.9 tures, fire, landslide, liquefaction and per- RS at 33 km depth, that occurred on com-

Earthquake Disaster of Yogyakarta and Central Java ... (Sutikno) 7 plexes faulted area, partly composed of The number of victims and damage houses various rocks/sediment and dense popu- in Bantul are much higher compare with lated area may caused higher victims and the others, because of the location is rela- damages. A large number of accompany- tively close to the fault complexes, dense ing earthquakes at shallow depth also have populated area and poor the building qual- psychological influences to the people in ity. Up to now some people still live in the stricken area. Damage assessment of tends, as a reason the rehabilitation and any disaster in large area usually get diffi- reconstruction programs of the houses do culties, because of accessibility of the re- not finish yet, and they still trauma with mote area and transport facilities. Table 2 the earthquakes occurrences. Beside the show temporary data of the victims and houses, some public facilities such as Table 3 show the damages due to the earth- school building, road and water supply also quake in Yogyakarta, in one week after damaged. Figure 4 shows spatial distribu- shock. The data do not cover yet the vic- tion of damage areas in relating to geologi- tims and the damages from Klaten district cal condition (Murwanto et al., 2006). of the Central Java Province. The recent data show that the number victim 5,048 Landslides due to Earthquake died, 206,524 houses damage, 2,014 small and medium industries damages, 2,371 Naturally the study area has medium school building and the financial loss for to high landslide hazard susceptibility. It is about 22 trillions rupiahs ($ 2,100 millions). supported by some factors, such as geo-

Table 2. Victim data of earthquake disaster of Yogyakarta ( data on June 2nd, 2006)

Number of victims Num. District House hold Persons Death 1 Bantul 227,030 77,251 4,121 2 Yogyakarta 48,244 195,456 178 3 Kulon Progo 18,081 74,592 22 4 Sleman 45,127 13.543 224 5 Gunung Kidul - - 84 Total 338,482 1,201,895 4,629 After Sutikno, 2006

Table 3. Damage data of houses and education facilities due to earthquake disaster of Yogyakarta (data on June 2nd, 2006) Houses damage Educational Num. District Totally Highly Slightly facilities damage damage damage damage 1 Bantul 71,482 70,718 66,497 158 2 Yogyakarta 7,161 14,536 21,192 386 3 Kulon Progo 4,477 5,176 8,999 662 4 Sleman 4,991 15,382 11,220 130 5 Gunung Kidul 13,543 4,716 16,742 84 Total 101,654 110,530 124,650 1,470

8 Forum Geografi, Vol. 21, No. 1, Juli 2007: 1 - 16 logic, geomorphologic, climatologically and past liquefaction occurrences are very use- land use type condition. By shaking of the ful to delineate and characterize areas of main earthquake some actual landslides liquefaction susceptibility for the future occurred in the hilly-mountainous area; rock earthquakes (Wakammatzu,2000). falls, landslide and slumping were identi- fied. Beside the actual, some potential land- Displacement of the Land Surface slide also are identified, especially on the area where the land surface or the rocks Another features as impact of the surface show some fractures. The such con- earthquakes are displacement on the land dition should be take into account when surfaces. Displacement of the land surface the rainy come. The spatial distribution of can be shown by fracture or fault on the the mass movement mainly on the steep hard rocks and or on unconsolidated sedi- slopes, along fault lines and along fault line ment. The displacements usually have im- scarps. pact to groundwater condition, land sub- sidence and landslide. Lowering of the Liquefaction groundwater level up to 4 meters occur in southern part of the area, while in another Liquefaction features or sand blows, sites new springs or seepage rise. occur when ground shaking during an earthquake liquefies a subsurface layer of Disaster Reduction sand which penetrates into/or through an overlying, otherwise impenetrable layer. In disaster management framework, The overlying layer is intruded via a sand risk reduction is important aspect. Disas- dike and if this layer is the uppermost strati- ter risk reduction is an effort to minimize graphic unit the liquefied sand can pen- the victim, property lost and environmen- etrate to the ground surface and can be ex- tal damages. Prevention, mitigation and pressed as mound or area of sand. The preparedness is component of the disaster original ground surface is commonly de- management to reduce the victims, the pressed as a result of the displacement of property and the environment before the the subsurface sand and water (Bryant, disaster occur. Relief, rehabilitation and 2005). During the Yogyakarta’s earthquake reconstruction is component of the disas- some liquefaction features occurred, espe- ter management during and after the oc- cially on alluvial plain, volcanic foot plain currence of disaster. and fluvio-volcanic foot plain units. Fea- tures of liquefaction in the study area are Reduction of earthquake disaster shown by sand blows to the land surface need hard effort, because the occurrence and sand blows through well. In certain area of the earthquake can not be predicted ac- the sand blows can produce one truck of curately and early warning system in some sand, and the sand blows trough well, the cases is difficult to execute. Mitigation is become shallower and it can not be used the effective way to reduce the impact of for domestic water supply anymore. Liq- the earthquake disaster. Mitigation of the uefaction is known to occur repeatedly at earthquake disaster can be carried out by the same site during more than one earth- structural and non structural efforts. quake, and the maps showing locations of

Earthquake Disaster of Yogyakarta and Central Java ... (Sutikno) 9 Structural effort to earthquake disas- lated area and most of the people relatively ter risk reduction is less effective than non poor in financial. Relating to the land use structural, because safety of building struc- regulation, there was local wisdom in reduc- ture is depends on magnitude of the earth- tion of earthquake. The local wisdom told quake. Building regulation is needed to ful- orally by old generation that the younger fill the minimum requirement for safety from generation should not build a house near by a certain earthquake magnitude that usually the river and should not used bricks mate- occur in the prone area. Structural efforts rial. This local wisdom was important mean- for rehabilitation of the damage houses in ing for risk reduction because if build the this area used building regulation guided by house near by the river faced with flood and local government. Rehabilitation of damage earthquakes disaster, because most of the houses organized and carried out in a group rivers in the southern part associated with of people who their houses were damage and fault. The faults in this area have high sus- each group was guided by a supervisor. Fi- ceptibility to earthquake hazard. nancial support for rehabilitation come from the government. At present the rehabilita- Public awareness of the community tion the houses do not complete yet. to the earthquake disaster commonly were very low, because they did not have experi- Non structural effort to earthquake enced with disastrous earthquakes. After disaster reduction usually used possible warn- the occurrences, the community just aware ing indicator, land use regulation, relocation that the area where they live were located of communities, public awareness and edu- in the earthquake hazard zone. The public cation program. Warning indicator for earth- awareness grew by experiences and social- quake, beside using seismograph record can ization that carried out by government used natural indicator. The natural indica- agency, university, research center and tor for earthquake commonly used bio-indi- NGO. Gadjah Mada University (GMU) is cator, groundwater level changes, electric the biggest university in Yogyakarta and resistivity of groundwater, rock cracking and Central Java has important contribution to earthquake cloud. The such natural indica- risk reduction on earthquake disaster. More tor did not take into account by the com- than 2 thousand of the GMU’s students and munity, because for along time there was no guided by lecturer gave socialization to the occurrence of significant earthquakes. Such community how to mitigate the earthquake as a vertical cloud feature in the southern disaster. The target of the socialization are side of the stricken area above the Indian the community members and pupils from ocean three days before earthquake was primary to high school. Education program meaningless by the community. After earth- was the effective way for socialization on quake shaking the area people just aware risk reduction of disaster. At national level, that specific cloud feature as indicator for government proposed curricula on disaster earthquake. in educational program, but at temporary inserted into geographic course. In risk re- Land use regulation and relocation duction of earthquake disaster or any types program was rather difficult to execute in of disaster, public awareness and educa- this area, because the stricken areas have tional program is more effective than the been occupied for along time, dense popu- others. It is not essay to maintain the aware-

10 Forum Geografi, Vol. 21, No. 1, Juli 2007: 1 - 16 ness of the community, commonly disas- more than the earthquake magnitude; ter is very vast to forget. In the earthquake disaster prone area it is important to main- 3. the main and the accompanying earth- tain of socialization program for risk reduc- quakes have multi-hazard impacts to tion, because the recurrent interval for the environment such as landslide, liq- earthquake take long time. uefaction, groundwater depletion and raising spring and seepages; CONCLUSIONS 4. due to dense populated area and the Discussing on the geologic, the geo- marginal condition of the financial sup- morphologic, the land use condition, earth- port rather difficult to make land use quake characteristics and its impact of regulation and relocation for risk reduc- Yogyakarta and Central Java disaster this tion from the earthquake disaster; paper concluded that: 5. awareness and education program for 1. disturbance of subduction zone of the the community more effective to Eurasian and the Indian-Australian mitigate the earthquake disaster; plates triggered earthquake and caused socialization program for risk reduction reactivated of the Opak fault system was important to maintain continually, then shook Yogyakarta and Central because disaster very past to forget. Java; geologically and geomorphologi- cally southern part of Yogyakarta and ACKNOWLEDGEMENTS east-southern part of Central Java as prone area to earthquake hazard; the The writer gratefully acknowledges damages areas associated with the fault to Mr. Jaya Murjaya for supporting earth- system; quake data, to Mr. Helmy Murwanto, Mr. Sutarto, Mr. Tono Saptono for supporting 2. the magnitude and the duration of the the geological information relating to the earthquake do not the only caused of earthquake; Mr. Danang Sri Hadmoko for the large number of victims and prop- preparing the English version of the geo- erty lost but the structure and the ma- logical map. Last but not least thanks to terial of building did; the duration of Professor Haruyama Shigeko (Tokyo Uni- earthquake shaking caused the larger versity) who gave a chance to joint sympo- number of victims and property lost sium on natural disaster.

REFERENCES

Abbott,P.L. 2004. Natural Disaster. McGraw Hill. Higher Education. Boston. BMG,2006. Characteristics of Earthquake Data of Yogyakarta Unpublished. Bryant, E. 2005. Natural Hazards. Cambridge University Press. Cambridge. Darman Herman and Hasan Sidi. F. (Edit). 2000. Outline of the Geology of Indonesia. IAGI. .

Earthquake Disaster of Yogyakarta and Central Java ... (Sutikno) 11 Hardjono, I. 2006. “Hirarki Gempa Bumi dan Tsunami (Aceh, Nias, Bantul, Pangandaran, dan Selat Sunda)”. Forum Geografi, Vol. 20, No. 2, Desember 2006. Hlm 135-141. Murwanto, H; Sutarto; Joko Susilo. 2006. Tinjauan Geologi. Dampak Gempa Tektonik terhadap Pola Rekahan dan Hancuran di Wilayah Jawa Tengah dan Daerah Istimewa Yogyakarta. Workshop. UPN. Yogyakarta. McGeary,D. Plumer,C.C. and Carlsons, D.H. 2004. Physical Geology. Earth Revealed. McGraw Hill. Higher Education. Boston. Sudarmadji. 2006. “Perubahan Kualitas Airtanah di Sekitar Sumber Pencemar Akibat Bencana Gempa Bumi”. Forum Geografi, Vol. 20, No. 2, Desember 2006. Hlm 99- 119. Summerfield, M.A. 1991. Global Geomorphology. Longman Scientific&Technical. New York. Sutikno, 2006. Disaster Management and Holistic Approach in Planning for Peri-Urban Area Development. International Seminar on Regional Planning for Disaster Prone Areas in South East Asia. November 20-24-2006. Gadjah Mada University. Yogyakarta. Verstappen, H.Th.2000. Outline of the Geomorphology of Indonesia. ITC. Enschede. The Netherlands. Wakamatzu, K. 2000. Liquefaction History, 416-1997, in Japan. Institute of Industrial Science, University of Tokyo, Japan. Wartono Rahardjo, Sukandarrumidi, Marno Datun, 1995. The Geological Map of Yogyakarta. Directorate of Geology. Bandung.

12 Forum Geografi, Vol. 21, No. 1, Juli 2007: 1 - 16 Appendix

Fig.1. Location of Yogyakarta Earthquake and Central Java in Tectonic Plate

Earthquake Disaster of Yogyakarta and Central Java ... (Sutikno) 13 Fig.2. Geological Map of Yogyakarta and Its Surrounding (After Murwanto, et.al., 2006)

14 Forum Geografi, Vol. 21, No. 1, Juli 2007: 1 - 16 Fig. 3. Seismicity of Java Island (A. In 2006 ; B. 1990-2006)

Earthquake Disaster of Yogyakarta and Central Java ... (Sutikno) 15 Fig. 4. Damage Area Relate to Geological Condition After 27th May Earthquake

16 Forum Geografi, Vol. 21, No. 1, Juli 2007: 1 - 16