EARTHQUAKE DAMAGE ASSESSMENT:APPLICATION AND VERIFICATION OF THE RADIUS
METHOD TO YOGYAKARTA EARTHQUAKE 2006
Kusworo Darpito∗
MEE09193

Supervisor: Kenji OKAZAKI∗∗
Shin KOYAMA∗∗∗

ABSTRACT
In order to reduce earthquake disasters, Indonesia needs a regional planning based on the disastermitigation. It is also necessary to make people aware of the risk of earthquakes. By using tool that cansimulate the damage caused by an earthquake, an increase in the public awareness of earthquake
hazards can be expected and it will enrich the regional planning based on disaster mitigation.
This study focused on the Yogyakarta Earthquake that occurred on May 27, 2006. This
study employed an application of RADIUS program to estimate the damage of the buildings andnumber of casualties in Klaten Regency. The estimated number of the damaged buildings was muchsmaller than the actual damage while the number of casualties was rather close.
Considering the limitation of the RADIUS method and the conditions in Indonesia, wemade some revision of the RADIUS program, such as: the effect by the movement of the fault into
attenuation, the higher vulnerability function of the brick masonry houses, the smaller casualty
coefficient of the temporary and semi-temporary houses, and the definition of the day time,
considering the actual intensities, construction methods, and life style in Klaten Regency. After theserevisions, the RADIUS estimate came to be much closer to the actual damage. The revised RADIUS
program is more suitable for Indonesia. It is expected that the revised program will be used in otherareas in Indonesia with slight modification, considering the differences in local conditions.
Keywords: Earthquake damage estimate, Yogyakarta Earthquake, RADIUS Program.

1. INTRODUCTION
In the phenomena of natural disasters, earthquakes occur almost every year in Indonesia,
causing many deaths and injuries and extensive property damage. However the impact of theseearthquakes can be reduced by disaster mitigation. For disaster mitigation, the participation ofgovernment and society is required. The government needs to raise public awareness of those who livein this earthquake-prone country: a big earthquake in populated areas could cause damages in many
residential houses. Many local people build their house without complying with earthquake resistant
standards. This study is expected to produce a program that can simulate the amount of damages
caused by an earthquake, reflecting the conditions in Indonesia.
2. DATAFor this study, we take data from the Klaten Regency in the Central Java Province before
earthquakes on Year 2005 and actual damages caused by Yogyakarta earthquake in 2006, as follows:∗Ministry of Public Work, the Republic of Indonesia.
Professor, National Graduate Institute for Policy Studies (GRIPS), Tokyo Japan.
∗∗∗International Institute of Seismology and Earthquake Engineering (IISEE), BRI, Japan.
∗∗− 85 −Total population and distribution by districts;
Total number of the buildings, building types and their distribution by districts;
Ground condition (soil type);
Casualties and damage of the building;
The data can be obtained from several sources, such as Media Center, the statistic agency(BPS) and National Coordination Agency for Surveys and Mapping. The Data include the number ofhouses, type of houses and their distribution in each district; we make some assumptions because oflimited information, while for the ground condition we can obtain information from the Local Statistic
Agency of Klaten and Geological Map of the Surakarta – Giritontro Quadrangles, Jawa release by theNational Coordination Agency for Surveys and Mapping (BAKOSURTANAL).
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3. METHODOLOGYThis study employs an application of RADIUS program to estimate the damage of thebuildings and number of casualties based on the earthquake, ground condition, demographic data andvulnerabilities functions. The program is very suitable for developing countries like Indonesia.
Earthquake Hazard will be estimated from parameters of the scenario earthquake and groundconditions. Damage will be estimated from hazard and the existing structures in the area calculated
from not only by the number of structures, but also by types of the buildings. Casualties such as deaths
and injuries are also estimated from the number of damaged buildings.
This study focuses on the Yogyakarta Earthquake that occurred on May 27, 2006, withmagnitude of 6.3 Richter scale, at 5:54 morning in Java local time. The depth was 10 KM, in SouthWest direction of Klaten Tengah, with epicenter at 31 Km from Klaten Regency (data source fromUSGS).
As for Klaten Regency the data on year 2005 are obtained, and we put into RADIUS programfor estimation, and then the estimation result will be compared with the actual damage caused by theYogyakarta Earthquake 2006. After comparison, we will make some proposal for revision of theRADIUS program.

4. DAMAGE ESTIMATIONThe earthquake hazard is estimated from the earthquake scenario and ground conditions. Damage isestimated from the hazard and the existing structure in the area, which depends not only on the numberof structure, but also on the types of the building or life line facilities, by using vulnerability functions
derived for each type of structure. Vulnerability functions reflect the relationship between seismic
intensity and degree of structure; casualty is estimated from the number of damaged buildings withinformation on the number of people inside building during the day and night. In Figure 1 , a generalflow of earthquake damage estimation by RADIUS Program, is shown
Scenario
Earthquake

GroundCondition
㻌

Earthquake
HazardDemographic
Data Inventory&Vulnerability

DamageEstimation

㻌㻌㻌
Earthquake DisasterReduction Planning(Preparedness)(Emergency Response)(Recovery) 㻌㻌㻌Figure 1. General flow of earthquake damage estimation− 86 −

While to estimate the damage caused by theearthquake, step by step as follow:
Step 1: Basic Data Inventory
1.1 Target region identification
Population in Klaten Regency as of 2005
: 1,286,058
Total number of buildings as of 2005
: 331,890
For identification Klaten Regency divided into 5(five) regions, as in figure:
1.2 Mesh/Grid :For this case study the scale mesh/grid is divided
into 1 km2, with total area of 656 km2.
1.3 Mesh numbering
In this case study the meshes are numberedusing integers between 1 and 656.

Figure 2. Map of Klaten Regency

1.4 Mesh ID
The RADIUS program automatically assigns Mesh ID
values to meshes from left to right and top to bottom.
1.5 Area ID
26 areas were defined, so that they represent eachdistrict.
1.6 Mesh weight
Mesh weight classification is related with building
density in Klaten Regency, based on the authors view.
1= between 100 and 400 building per km22= between 400 and 750 building per km2
3= between 750 and 1,500 building per km2
4Ӌ 1,500 building per km2
Step 2: Soil Amplification Setting
The user enters the local soil type classifications in theBasic Input Data sheet, for each of the mesh in the target
region, such that:0= Unknown
1= Hard Rock/Bed Rock2
= Soft Rock3
= Sedimentary Rock/Average Stiff Soil
4
= Soft Soil/ Land Fill/ Reclaimed Land
Step 3: Structure inventory setting
Because the data is not complete enough, to obtain thenumber of houses in each district, an assumption has
to be made.
Building Classes
In the Klaten Regency building classes are divided into
7 types of buildings.
Step 4: Arranging population distribution
Klaten regency is divided into 26 districts withdifferent number of population and density. Total ofpopulation in 2005 is 1,286,058.

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Figure 3. Mesh weight distribution

Figure 4. Soil Type Distribution Map in theKlaten Regency

Step 5: Defining Scenario Earthquake
For this case study we used the attenuation equation from Joyner & Boore, because this attenuation
equation is used for shallow earthquakes (Yogyakarta earthquake is relatively shallow). For thescenario earthquake, we used the Yogyakarta Earthquake in May 27, 2006, with magnitude of 6.3, at5:54 AM local time in Java, and the depth was10 km, and epicenter 31 km with direction in the SouthWest of Klaten Regency according to the source data from USGS. The reference mesh is determinedas 289, which is supposed to the center (down town) of Klaten Regency.
Step 6: Calculation of base rock motion and surface motion and converted into PGA, andconverted into MMI
By using the attenuation equation from Joyner & Boore, the maximum intensity was in the Prambanan
District with the average MMI of 7.2. For the minimum intensity was in the Wonosari, Klaten Tengah,Kalikotes, Juwiring, Karang Dowo and Bayat Districs with the average MMI of 5.9. The differences of
the intensity are influenced not only by the distance from the epicenter but also by the local soil
conditions.
Step 7: Calculate damage to the building
The number of buildings damaged is 20,231. The result shows the highest damage percentage and total
number of buildings damaged in Ramadan District, and the lowest in Kalikotes District.
Step 8: Calculate Casualties
It is described that there are about 12,642 people (approximately 0.98 % of the total population) who
will be injured and about 861 people (approximately 0.07 % of the total population) will be dead by
the earthquake. In this estimate, buildings were damaged largely in Prambanan District. Thus, thecasualties in this district are also larger than other districts.
Step 9: Summarize Results
The largest damaged buildings, deaths and injuries are found in Prambanan District and the lowest inKalikotes District.
5. COMPARISON
The damages calculated by the RADIUS Program are both collapse and heavy damage, lightdamage is not considered. In this study, comparison will be made based on building collapse andmajor damage data from media center. Thus, lifeline damage is not considered.
In some district the media center data is greater than RADIUS result, and the largest
damaged was Gantiwarno District (11,919 buildings damaged) but the largest damaged based on
RADIUS result was in Prambanan District (2,140 buildings damaged). Overall comparison founddifference of 75,534 about the buildings damage, which is approximately 78.87 %, as shown in table 1.
RADIUS results for casualty are close to the actual events (table 2). In the data of death tollfrom Media Center, the biggest death toll was found in Wedi (319 people) and for injury it was in
Gantiwarno District (9,136 people). From RADIUS Program, however, the highest casualties arefound in Prambanan District (death 163 people and injury 2,061 people).

Table 1. Comparison of damage of thebuildings

Table 2. Comparison of casualties− 88 −

6. PROPOSED REVISION OF RADIUS PROGRAM
6.1 Attenuation Equation
The USGS data on the event of the Yogyakarta Earthquake says that result of the average MMI in theKlaten Regency is 9, the average intensity observed by Dwikorita Karnawati et al. are also higher than
RADIUS Program(between 7.3 and 8.3), but the result of this program is about 6.28 MMI. In reality,
there is a movement of the fault from epicenter to the Klaten Regency, particularly in the Gantiwarno
District and Prambanan District, but the RADIUS program does not consider this condition. In the casethat the earthquake is very close and shallow, the adjustment of attenuation equation is necessary. Inorder to simplify this process, it is attempted to make changes to the epicenter distance from 31 km to
20 km to obtain the similar intensity.
6.2 Building Damage Coefficient
To conform to the condition in Indonesia, wereplaced vulnerability coefficient function fordamage to the building type RES 2. The replacing
coefficient of vulnerability function for damage tothe building adjusted to the conditions in Java.
References used to replace this coefficient are basedon the paper written by K. Meguro. In the paper, therelation between buildings collapse and intensity formasonry houses obtained from the field surveys isshown as the figure 5. Because the curves only
represent the masonry house, we decide to change tothe coefficient of vulnerability function for the RES 2
in the program.

Figure 5. Fragility function of masonryhouses in java by K. Meguro

6.3 Death Coefficient Ratio
According to the building condition in Klaten Regency, people commonly build their house byutilizing the light materials for the roof and walls, such as bamboo, woods, zinc tile and clay tile whichis made by the traditional method in Indonesia. It is expected that less people will be killed by collapseof this type of buildings. Therefore, it is attempted to change the casualty coefficients in the RADIUS
Program by decreasing the coefficients of the RES1 by half.
6.4 Definition of Day Time
In Indonesia most people are Muslims, so in the early part of days, they go to a mosque to pray. Then,
their activities are usually outside the house starting from early morning around 5 am. Therefore achange of the day-time, adjusting to the habits of the society in Klaten Regency, is needed. Day time inthe RADIUS Program is defined as from 6 AM to 6 PM and night time is defined as from 6 PM to 6AM, but with regards to the habits of society in Klaten District we change day time from 5 AM to 6
PM and night time from 6 PM to 5 AM.
6.5 Result after revision
After making changes in above, the results of the damage amount came much closer to theactual damage amount from 20,231 to 54,148, as shown in table 3. Changes in the day-time adjusted tothe actual life style of local communities and also in the coefficient of casualty can be affecting to thenumber of the death and injured are quite close to the actual event, as shown in table 4.

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Table 3. Comparison of damage of thebuildings

Table 4. Comparison of casualties

7. CONCLUSION
We calculated building damage and casualties caused in Klaten Regency which was severely hit
by Yogyakarta earthquake 2006. RADIUS estimate is smaller than actual buildings damage andcasualty was close to the actual damage, however there are some revisions to be made, as follows:
1. The effect of the movement fault from the epicenter towards the Klaten Regency during theearthquake was not reflected in the RADIUS program. In this program, attenuation equation would
not represent the actual intensity well as the epicentre is very close and shallow. Therefore it isnecessary to consider this kind of effect in the RADIUS program.
2. Vulnerability functions of the buildings damage in this program need some change to adapt to theconditions on Klaten Regency. We increased the coefficient of RES 2 so that it becomes 30 %more fragile than the original condition.
3. According to the building condition in Klaten Regency houses are made by light materials,
therefore we decreased the death coefficients RES1 to half.
4. The day time must be adapted to the actual life style in Klaten Regency
We made some changes in the vulnerability coefficient function for damage of the building, theintensity, casualty of death coefficients and the day time in the RADIUS Program so that it can beadapted to the conditions in Indonesia. Tentatively this program may be used for Klaten Regency andJava Island, where the housing condition are similar to Klaten Regency, but we still need other casestudies to ensure that this revised program can be used for all over in Indonesia. It is expected that theprogram is disseminated to raise public awareness on the seismic risk in Indonesia.
AKNOWLEDGEMENT
I would like to express my sincere gratitude to the supervisor, Professor Kenji OKAZAKI, for his
continuous support, valuable suggestions and guidance during my study. I want to thank Dr. Shin
KOYAMA, my Advisor, for kindly helping me and having taken very good care.
Finally I would like to thank Mr. Nur Tjahjono Soeharto, for giving me necessary
information from Klaten Regency regarding to this study.
REFERENCES
Karnawati D., Pranumijoyo S., Anderson R., Husein S., 2008, the Yogyakarta Earthquake of May 27,
2006.
Meguro, K., 2008, “Technological and Social Approaches to achieve Earthquake Safer
Non-Engineered Houses”, Journal of the World Conference on Earthquake Engineering October
12-17, Beijing, China,
BAPPENAS (National Development Planning Agency), 2006, Preliminary Damage and Loss
Assessment Yogyakarta and Central Java Natural Disaster, A Joint Report from BAPPENAS, theProvincial and Local Governments of D.I.Yogyakarta, the Provincial and Local Governments ofCentral Java, and international partners, June 2006.
Kaneko F., OYO International Corporation, RADIUS Program Methodology
BPS- Statistics of Klaten Regency, Klaten in Figure 2005

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