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Chapter I
Introduction

1.1

Background

After tsunami hazard predominantly damaged Nanggaroe Aceh Darussalam
(NAD) Province in December 2004 and Earthquake in The Special Region of
Yogyakarta in 2006, those cases increase the awareness impact of natural hazard
for many stakeholders. Natural hazard have wide terms, but common case have
been caused by geological hazards. Geological hazards are dangerous situation
caused by geological processes (Noor, 2006). The kinds of geological hazards are
landslide, mountain eruption, earthquake, flooding, erosion, salination, and
drought (Noor, 2006).

Geological hazard caught avoided by hazard mitigation. The concept of hazard
mitigation is decreasing risk from geological hazard with impacts on property
damage and death toll (Noor, 2006). Spatial planning must consider about hazard
mitigation, because it consists of land use arrangement; such as allocation of
settlement area, industrial area, conservation area, etc. Analyzing land allocation
in spatial planning based on geological hazard has objective to prevent from
natural hazard damaging.

Spatial Planning Act No. 26 /2007 describes about how to hazard tackling with
determine hazard vulnerability area. In article 42 verse 1: implementation and of
spatial planning have been done to decrease hazard risk, which consist of applying
spatial planning regulation, safety standard, and apply sanction for scofflaw.

To determine hazard vulnerability area in spatial planning is developed using
many factors. Most of the factors are related to geological information map.
Geological information map contains some information, which is related with the

1

stability of area from impact of geological hazard. Types of geological
information are: structure and physical properties of rock, slope, earthquake
intensity, and

existing fault line. All those factors have close relation with

stability of area, or describe underground condition. On the surface, existing land
use, characteristic demographic of population and economic are the most factors
affected in vulnerability from earthquake hazard.

Combination between susceptibility from (geological) hazard cause by earthquake
and vulnerability is defined as a risk (Figure 1.1). Risk means the expected
number of lives lost, persons injured, damage to property and disruption of
economic activity due to a particular natural phenomenon, and consequently the
product of specific risk and elements at risk (UNDRO, 1979) (Fournier, 1986) in
Kjatsu,

(2005). Risk assessments in urban area have benefit to help and

clarify decision making for disaster management and the development of
mitigation strategies (Khatsu,

. (2005).

Figure 1.1 Risk concept; Function Hazard and Vulnerability

Two ways analysis have been done; first is hazard analysis, which measured from
geological information (rock structure, slope, earthquake intensity, geological
structure, and existing fault line), and second is vulnerability analysis which
measured and compared all criteria’s (physical, demographic, and social), and
produced rank of priority distribution vulnerability area.

It is difficult to make decision that involves many factors or information, and to
solve the problem for decision making concept. Decision making is a process of
choosing among alternative courses of action for the purpose of achieving a goal

2

or goals (Turban, 1995).
). SDSS can be defined as an interactive, compu
omputerCbased
system design to support
supp
a user or group of users in achieving
ving a higher
effectiveness of decision
ision making while solving a semi structured spatial decision
problem (Malczewski,
ki, 1999).
1999)

1.2

Statement of Research
Rese
Problem

Earthquake is a deadly
dly hazard
ha
in 20th millennium (UN, 2010), because
cause it cannot
be predicted when it come
com and what level of strength. BNPB (2007)
2007) recorded
from 2002 to 2006 that ea
earthquake and secondary impact of earthquake;
hquake; tsunami,
caused at least 120.000 death victims, and more than 600.000 houses
hous were
damaged in Indonesia. Those
Thos facts describe at least 90% total from
om other
othe hazard
like flood, drought, landsl
landslide, and etc.

umber of death victim caused by natural hazard (BNPB,
NPB, 2007).
2
Figure 1.2 Numbe

3

Figure 1.3 Number of housing damage caused by natural hazard (BNPB, 2007).

Level of urbanization in Indonesia is still increasing; at least 119 inhabitants per
square kilometer is the population density in Indonesia, and particularly in Jawa
and Bali islands were 996 inhabitants per square kilometer (BNPB, 2007). The
Population growth followed by the increase of built up areas, can increase
vulnerability and risk level from natural hazard. As tool for development control,
spatial/urban planning has strategic position in mitigation concept to avoid natural
hazard.

One of the mitigation concepts to avoid high loss caused by earthquake is to
develop spatial planning based on natural hazard potential and vulnerability
factors. In facts, not all cities in Indonesia prepare spatial planning based on
natural hazard potential and vulnerability factors. Existing locations in Indonesia
are surrounded by tectonic and volcanic activities, which should be the priority
review for urban planning.

The latest spatial planning guide in Bantul, which was revised in year 1999, has
some refraction especially in determining for hazardous area. For example, in sub
district Sewon, Kasihan, and Banguntapan were set to urban settlements area. In
facts, in those area loss rates had reached high enough when earthquake occured
in 2006. The loss rate was more than 4660 fatalities, and 2000 victims injured. For
4

structure, the level of damage reached more than 21000 houses damaged, and
15000 were totally destroyed. Those situations require arrangement based on
earthquake hazard and vulnerability which aims to reduce lost in the future.

1.3

Aim of Research

This study has a purpose to define and describe about risk, which function of
hazard and vulnerability area related to support urban planning process. Until
now, there is not any clear term of risk, hazard, and vulnerability area noted in
determine in spatial context. In this case, to determine risk has two combinations
between hazard and vulnerability area.

1.4

Objective of Research

Objectives of this study are:
1.

To determine hazard area based on geological information by using GIS
spatial analysis.

2.

To determine vulnerability area based on physical, demographic and social
factors using multiCcriteria analysis.

3.

To determine level of risk area by combining hazard map and vulnerability
map.

1.5
1.

Research Questions
How to determine hazard, vulnerability, and risk area map based on
geological information by using GIS spatial analysis?

2.

Which location is potentially susceptible from earthquake hazard?

3.

Which location is vulnerable when earthquake occurs? Vulnerability was
observed from physical, demographic, and social factors.

4.

How big is the risk probability degree in all area based on earthquake
hazard, and related to the spatial planning guide.

1.6

General Research Methodology

It generally has been shown in schematic research methodology flow chart in the
figure 1.4. The whole research work was divided into three major parts. First part

5

of methodology deals with review hazard and vulnerability literature particularly
determined the criteria. The criteria should represent in spatial format data which
will be used for spatial modeling.

The second part of methodology deals with multiCcriteria analysis, which use
pairwise comparison method (PCM) to assign criterion weighted. The third part of
methodology deals with modeling with spatial analysis using GIS capability,
which criteria weighted resulted from multiCcriteria analysis is used to simulate in
spatial analysis with weighted overlay method.

Figure 1.4 Schematic diagram of research methodology

1.7

Scope of Research

This research is focusing how to determine hazard, vulnerability, and risk area
with simulation in GIS. GIS spatial analysis is used to simulate for hazard map
model which represent geological information combination. The vulnerability
map used was physical, demographic, and social aspects.

A.

Hazard Analysis

Geological information is described in attribute and map (spatial data), and it was
produced by Center of Vulcanology and Geological Hazard Mitigation, Ministry

6

of Mineral and Energy Resources. The geological information is classified into 5
(five) information:
1.

Rock Structure and Physical Characteristic.

2.

Geomorphology (Slope and Relief).

3.

Existing fault line.

4.

Earthquake Intensity.

B.

Vulnerability Analysis

Vulnerability analysis consist of 3 (three) factors; physical, demographic
(demographic of population), and social.
1.

Physical Factor
Representative of physical aspects in urban risk analysis can be divided in
three categories: density of built up area, number of structure, and type of
structure.

2.

Demographic Factor
The main factor of demographic vulnerability is described in characteristic
demographic population that represents some data; 1) Total population, and
2) Density distribution, and 3) Population growth rates. Those criteria will
transform into spatial data, which is subCdistrict administrative as a boundary
unit.

3.

Social Factor
Representative of physical aspects in urban risk analysis could be
differentiated in three categories; 1) low income distribution, 2) Gender, and
3) Age structure (elderly and children).

C.

Risk Analysis

Risk is the function of hazard and vulnerability, it means that the combination
between hazard map and vulnerability map will produce risk map. Risk is
multiplication between hazard and vulnerability function, which can be expressed
in the following mathematical form:

Risk = Hazard x Vulnerability

7

(1)

1.8

Location of Research

The research location was in the Bantul Regency, Yogyakarta Province. The
coordinate geographic position was in latitude 07°44'04" S C 08°00'27" S, and
longitude between 110°12'34" E C 110°31'08 E. The climate was influenced by sea
in south (Indian Ocean), and the majority of land used for settlement and
agriculture. Topographic conditions were steep in the west side, and flat in rest
area such as coastal area.

Figure 1.5 Location of Research

The capital city of Bantul Regency located in District Bantul. Bantul regency
consists of 17 districts. Bantul Regency has boundary with Yogyakarta and
Sleman City in north, Gunung Kidul in east, Kulon Progo in west, and Indian
Ocean in south. Some area were parts of expansion from Capital of Yogyakarta,
where located in north Bantul (Subdistrict Kasihan, Sewon, and Banguntapan).
It’s not surprising that the location is grouped into rapid development areas.

8

1.9

Research Output

The main output this study is;
1) Hazard area map based on geological information (ground stability), which is
susceptible from earthquake.
2) Vulnerability area map based on multiCcriteria analysis.
3) Risk map, which is the combination between hazard map and vulnerability
map. Risk map is used to assess the spatial planning map that already exists.

1.10

Limitation of Study

This research is focus on hazard, vulnerability, and risk area from impact of
earthquake hazard. Some limitation based on early investigated explain the
limitation of this study are;
1.

In the world, vulnerability concept is multiCinterpretation; it wasn’t consensus
to exactly define the meaning of vulnerability. That fact cause vulnerability
analysis cannot use single solution problem, or as problems which possess
multipleCsolutions and contain uncertainty about the concepts, rules, and
principles involved to reach these solutions (Rashed and Weeks, 2003)
(Cutter,

L.S., Boruff, J. B., and Shirley, L. W., 2003). So, in this research

tried to generate the criteria related with hazard (earthquake) vulnerability,
especially to determine the criteria. Widely examination of relevant literature
was used to select the criteria.
2.

Some of spatial data are not in the same basic scale or source, and it can
decrease spatial accuracy. For example geological map has a scale of
1:100000 while administrative map has a scale of 1:25000.

3.

To transform nonCspatial data (in example; density of population) to spatial
information used sub district administrative boundary as spatial analysis unit.
The application theory to mapping statistical data was explained by Menno,
Kraak J., and Ormeling F. (2009), which defined as choropleth map.
Choropleth map a thematic map in which areas are shaded or patterned in
proportion to the measurement of the statistical variable being displayed on
the map, such as population density or perCcapita income (Wikipedia, 2010).

9

Chapter II
Hazard Analysis: Ground Stability Analysis in
Urban Area

2.1

Introduction

Earthquakes are considered as natural hazards, which become the main interest of
environment experts. Impacts of earthquakes are producing environment physical
damage until cause of death. Refers to BNPB (2007), the impact of earthquake
caused at least 120.000 death victims among 2002 to 2006. That impact also
brought economic loss and regional development incline. Experiences in Aceh
tsunami (2004), Yogyakarta earthquake (2006), and the newest occurrence in
Padang (2009) made experts to reach solution to minimize the impacts of
earthquake.

The effort to avoid impact of earthquake hazard uses mitigation approach, which
can be depend as an activity to avoid impact of natural hazard or manmade hazard
for public and nation (Sutikno,

(2006)). Mitigation is divided into two

important parts, structural and nonCstructural. Structural mitigation is done by
structural approach such as land suitability, building resistance, type of material
structure, and etc. Non structural mitigation is done by “soft structure” such as
dissemination, education, training, institution development, etc. Both of concepts
should parallel in those implementations.

Spatial planning is a part of nonCstructural mitigation, which considers all of
hazard and the impacts. Based on hazard and the impacts, land use planning and
regulation should consider hazard potential and susceptibility. In case of
earthquake hazard, geological information and phenomena are important factors
to support what we should do and determine on the surface.

10

Spatial planning process must be supported by geological information to identify
where location susceptible from earthquake hazard. By using geographic
information system (GIS) can manage and utilization of (earthquake) hazard
information (DGME, 2004). Spatial analysis capability in GIS is possible to
produce hazard map, which is become important part in land use planning
process.

2.2 Objective of Research
The objective of earthquake hazard in this research to determine hazard area based
on geological information by using GIS spatial analysis. Geological information
consist of 4 (four) main factors which influence to ground stability; rock structure,
slope, earthquake intensity, and fault way.

2.3 Literature Review

2.3.1 Definition of Hazard
Hazard is potentially damaging physical event, phenomenon, or human activity
that may cause the loss of life or injury, property damage, social and economic
disruption, or environmental degradation (ISDR, 2007). Following the ISDR term,
hazard can include latent conditions that may represent future threats and have
different origins: natural (geological, hydroCmeteorological and biological) or
induced by human processes (environmental degradation and technological
hazards). Hazard can be single, sequential or combined in their origin and effects.
Each hazard is characterized by its location, intensity, frequency and probability
(ISDR, 2007).

2.3.2 Geological Hazard
One of the types of hazard is cause by natural factor. As mentioned by
International Strategy Disaster Reduction (ISDR), natural hazard is classify into 3
(three) types; by geological, hydro meteorological, and technological hazards.
Geological hazards are dangerous situation caused by geological processes. The

11

kinds of geological hazards are landslide, mountain eruption, earthquake,
flooding, erosion, salination, and drought (Noor, 2006).

The types of geological hazard which have often been occurring are cause by four
factors; soil movement, mountain eruption, debris avalanches, and earthquake
(Noor, 2006). That kind of geological hazard is the main hazard which cause more
property damage and death toll. In this research study, the focus is in geological
hazard caused by earthquake.

2.3.3

Earthquake

Earthquake is a shaking and trembling of the crust of the earth, caused by collision
between ground plates, active fault from volcanic activity, and detritus of rock
(BNPB, 2007). An earthquake is a sudden, rapid shaking of the earth caused by
the breaking and shifting of rock beneath the earth's surface (Earthquake, 2007).
Earthquake is an energy released phenomenon that cause dislocation in the inside
part of earth with instant change.

Refer to USGS (2008), term of earthquake is the vibration, sometimes violent, of
the earth's surface that follows a release of energy in the earth's crust. This energy
can be generated by a sudden dislocation of segments of the crust, by a volcanic
eruption, or event by manmade explosions.

The main causes of earthquakes (BNPB, 2007) can be classified as follows:
1.

Tectonic activity caused by ground plate displacement.

2.

Fault activity in earth surface.

3.

Local geomorphologic displacement, for example soil detritus.

4.

Volcanic activity.

5.

Nuclear explosion.

12

Figure 2.1 Illustration earthquake caused by tectonic activity (Bakornas PB,
2007).

Earthquakes can occur at any time without warning. An earthquake sequence
happen in the place where earthquakes occurred in the past and it will happen
again (Earthquake, 2007).

2.3.4 Impacts of Earthquake
The impact of earthquake depends on many factors related to ground seismicity
and activities on the surface. The factors depend on each other’s and it can
strengthen the earthquake. The most earthquake effect is building damage caused
by ground shaking and trembling.

Refers to Bell (Bell, 1999), the most serious direct effect of earthquake in terms of
building and structures is ground shaking. Researchers prove ground condition is
a main factor shaking effect and it cause damaging for building and structures.
Although building and structures standing on the firm bedrock, it can still be
affected, so the susceptible buildings should not be located near to a fault trace.
The most effects caused by earthquake classify into 4 (four) types (Upseis, 2008):

1.

Ground Shaking

Buildings can be damaged by the shaking itself or by the ground beneath them
settling to a different level than it was before the earthquake (subsidence).

13

Figure 2.2 Friday earthquake in
Anchorage, Alaska (Walker, 1982)

Figure 2.3 The ruins in
Yogyakarta Province, 2006.

Bantul,

Ground Displacement

2.

The second main earthquake hazard is ground displacement (ground movement)
along a fault. If a structure (a building, road, etc.) is built across a fault, the ground
displacement during an earthquake could seriously damage or rip apart that
structure.

3.

Flooding

The third main hazard is flooding. An earthquake can rupture (break) dams or
levees along a river. The water from the river or the reservoir would then flood the
area, damaging buildings and maybe sweeping away or drowning people.
4.

Fire

The fourth main earthquake hazard is fire. These fires can be started by broken
gas lines and power lines, or tipped over wood or coal stoves. They can be a
serious problem, especially if the water lines that feed the fire hydrants are
broken, too.

2.3.5

Yogyakarta (and Bantul) Earthquake

Yogyakarta earthquake occurred on 27th May 2006, which destroyed all
settlements and public facilities surrounding Yogyakarta. The strike hit not only in
Yogyakarta city, but it happened also in Bantul and Klaten regencies. Those areas
have high density population, and affected to a number of death tolls.

14

The epicenter Yogyakarta earthquake located in the west side of Opak fault line,
which has geographic coordinate; 8.24º S and 110.43º E (USGS, 2006) in Haifani,
. (2008). Alongside that coordinate is the central of damaging, which was
through in Merapi alluvial materials formation. That formation are consists of
alluvial, tuff, breksi, agglomerate, and lava current (Haifani, 2008).

Figure 2.4 Epicentrum Yogyakarta Earthquakes (UNOSAT, 2006)

The numbers of victims in Yogyakarta earthquake were 4,680 people killed, and
19,897 injured (Table 2.1). The administrative area has a lot a number of death
tolls located in Bantul Regency with 4,141 people, that statistic is over than 90
percent all sum of dead people. Almost the dead victims were caused by struck
down of building materials.

Table 2.1 Victim Data in Yogyakarta Earthquake
No.
1.
2.
3.
4.
5.

Local Government
Bantul
Sleman
Yogyakarta
Kulon Progo
Gunung Kidul
Total

Victims
Death
Injured
4.121
12.056
232
3.789
204
318
22
2.678
81
1.086
4.660
19.927

Source: Yogyakarta Earthquake Media Center (2006) in Haifani,

15

. (2008).

Yogyakarta earthquake also caused a lot of destruction of many houses in some
area. Bantul has the highest number of damaging houses compared to other areas,
at least 96,360 houses were totally damaged (totally loss), and 70,769 heavily
damaged (Table 2.2).

Table 2.2 Number of house damage in Yogyakarta Earthquake
No.
Local Government
1.
2.
3.
4.
5.

Bantul
Sleman
Yogyakarta
Kulon Progo
Gunung Kidul
Total

Number of House Damage
Totally
Heavy
Light
Damage
Damage
Damage
71.482
71.718
5.243
16.003
7.161
14.535
4.527
5.178
7.746
10.670
96.159
118.104
156.568

Source: Yogyakarta Earthquake Media Center (2006) in Haifani,

. (2008).

2.4 Methodology

2.4.1

Method of Research

The method of research mapping earthquake hazard is shown in figure 2.5. First
part research method is to review and identify hazard potential factor. Those
factors were selected and examined by geological experts, which was explained in
manual of spatial planning for mountain eruption vulnerability area, and
earthquake vulnerability area. Rock structure, slope (and relief), earthquake
intensity, and geological structure are the most affected when earthquake occurs.

Figure 2.5 Schematic diagram of ground stability mapping methodology

16

2.4.2

Review and Identify Earthquake Hazard Criteria

There are many criteria related to earthquake hazard that can determine the level
of damage. Most of the researchers believed the closeness to fault way were the
most important criteria in earthquake hazard (Bell, 1999, ITC, 2005, BNPB, 2007,
Erdik, 2007). Bell (1999) explained although a land had solid firm bed rock
wasn’t effect when in the land had or through fault way. Some experiences
describe which higher damage area located near or precise in fault way.

Fault Way
Fault way is the vulnerable place when interCplate movement and intraCplate
movement occur, which is divided into two categories; horizontal and vertical
movements (Gulati, 2005) (Figure 2.6). The movement plate in fault way is the
primary threat, which causes ground shaking effect. The bigger intensity in
ground shaking cause higher damage for building and infrastructure (Bell, 1999).

(a) Dip Slip Fault

(b) Dip Slip Fault

(c) Strike Slip Fault

Figure 2.6 Type of slip plate movement at fault (Kadarisman) (Gulati, 2005)

Earthquake Intensity
Second criterion which is important in earthquake hazard is earthquake intensity.
Earthquake intensity is the function of magnitude, distance from epicentrum,
vibration time, earthquake deep, soil condition, and structure condition (PIRBA).
The measurement of earthquake intensity states in mercalli modified intensity
(MMI). Earthquake intensity is closely related to another intensity criteria; gravity
force (α), and richter scale (Table 2.3). Levels in MMI scale can be described as
follows in state earthquakes (Table 2.4).

17

Table 2.3 Earthquake intensity, gravity force, and richter scale
MMI
i, ii, iii, iv, v
vi, vii
viii
ix, x, xi, xii

α
< 0,05 g
0,05 – 0,15 g
0,15 – 0,30 g
> 0,30 g

Richter
6,5

Source: Ministry of Public Work, Rep.of Indonesia (2007).

Table 2.4 Descriptive Scale of Earthquake Intensity in MMI

MMI
I
II
III
IV
V
VI
VII
VIII
IX
X
XI
XII

Descriptive scale of earthquake intensity
Not felt
Felt by persons at rest
Hanging object swings; vibration like passing light trucks
Vibration like passing of heavy trucks
Felts outdoors; awake sleepers; unstable objects move
Felts by all; glassware broken; books of shelves
Hard to stand; noticed in cars; damages some masonry
Collapses some masonry; moves some frame housing
General panic; foundation damage; cracks in ground
Most structures destroyed; landslides; water thrown
Rails greatly bent; underground pipes out of service
Damage nearly total

Source: FEMA

Slope
Slope is a dangerous potential factor when earthquake occurs. Rock and soil
movement under influence gravity could trigger earthquake ground shaking
(USGS, 2001). In some slope condition, rock and soil movement become
dangerous when earthquake occurs. Landslide follows with soil and rock fall is
main the threat when earthquake occur in slope area. Degree of slope represents
threat when earthquake occurs; it is more extreme can decrease the level of hazard
effect. Table 2.5 shows the degrees and description of slope classes.

18

Table 2.5 Slope classification
No

Percent of Slope

1.
2.
3.
4.

0–7%
7 – 30%
20 – 140%
> 140%

Information
Flat
Moderate Steep
Very Steep
Very very steep

Source: Ministry of Public Work, Rep.of Indonesia (2007).

Rock Structure
Strength of rock from earthquake effect depends on physical characteristic;
cohesiveness and material configuration. Those factors influence to reduce
vibration and ground shaking from earthquake effect, and then secure structure
from damage. Rock structure and strength from earthquake effect are classified
into 4 classes (Rudi Suhendar, 1998) (Table 2.6).

Table 2.6 Rock type classification from earthquake resistance and
Landslide probability
No

Classification

Rock Type

1.

I

2.

II

3.
4.

III
IV

Andesite, Granite, Diorite, Metamorf, Vulcanic Breccia,
Aglomerate, Sediment Breccia, Conglomerate
Sandstone, AndesiteCBasaltic Tuff, Silt Stone, Arkose,
Greywacke, Limestone
Silt Sand, Mudstone, Marl, FineCGranide Tuff, Shale
Clay, Mud, Organic Clay, Peat Moss

Source: Ministry of Public Work, Rep.of Indonesia (2007).

Rock classification is divided into 4 (four) classes, class I has the most solid
physical structure, and class IV have physical weak or it’s not resistance from
ground shaking and slip fault.

2.4.3 Data Preparation and Processing
Various spatial data were prepared and used to build hazard model. The spatial
data which was used to hazard modeling, based on geological and topographical
map, which is produced by government institution (Table 2.7). The data used for

19

this research were acquired from previous geological and topographic research
report. The spatial precision and validation were done by each institution.

Table 2.7 Main data hazard research
No.
1.
2.
3.
4.
1)
2)

Information

Type of
Scale
Source
Data
Rock Structure
Polygon 1:100,000
ESDM 1)
Slope
DEM
30 X 30 meters SRTM 2)
Earthquake Intensity
Polygon 1:100,000
ESDM
ESDM
Existing Fault
Polygon 1:100,000
Ministry of Mineral Resources and Energy – Republic of Indonesia, Center for
Volcanology & Geological Hazard Mitigation.
Shuttle Radar Topographic Mission (SRTM). 30 meter spatial resolution.
http://www2.jpl.nasa.gov/srtm/dataprod.htm.

Figure 2.7 Map of Rock Type and Structure in Study Area

20

Year of
Published
2007
2007
2007
2007

Figure 2.8 Map of DEM visualization by SRTM in study area

Figure 2.9 Map of Earthquake intensity in study area
21

Figure 2.10 Map of Fault line in study area

2.4.4

Multi Criteria Analysis

MCDA or could be defined as MCDM (multi criteria decision making) techniques
have largely been aspatial (Malczewski, 1999), but they are different in GIS
context. Spatial MCDA which is applied in GIS requires both data on criterion
values and the geographical locations of alternatives (Malczewski, 1999).

According to Malczewski (1999), the main concept combination between MCDA
and GIS is to support the decision maker in achieving greater effectiveness and
efficiency. Some technique used to support MCDA in decision making by using
decision rules, to choose the best or the most preferred alternatives. There are
some decision rules to tackle MCDA/MCDM in this research.

Decision Rules; Weighted Linear Combination
The main method in weighted linear combination (WLC) assigns relative weight
to each attribute (Malczewski, 1999). Decision maker directly assigns weights to

22

each attributes. The highest overall score is chosen for the alternative. The
following weighted linear combination formula:

(2)

Wt = Σi Wi.Xi ……Wn.Xn
Where; Wt = Total Weight
Wi = Weight value in each parameter i to n
Xn = Score value in each parameter i to n

Hazard Analysis
Simple weighted method will be used to produce hazard vulnerability map,
compose geological spatial information which has score and weighted value based
on reference (Table 2.9). The combination between score and weighted value in
geological information determines the level of ground stability. Ministry of Public
Work Government of Indonesia (2007) has classified the level of stability into 3
(three) classes which are; not stable, less/moderate stable, and stable. Each class
has cumulative score based on the combination between attribute values in
geological information (Table 2.8). The equation of hazard analysis related with
ground stability shows below:

=∑

(3)

Where;
Hazard zone based on ground stability, resulted by weighted overlay
in GIS
= Total weight rock structure
=Total weight slope
= Total weight earthquake intensity
= Total weight geological structure

Geological information has score and ability value. Weighted value has range
value 1 up to 5. Value 1 indicates the high importance level of geological
information, which means that geological information, is really necessary to know
the natural hazard zone (Table 2.9).

23

Table 2.8 Weighting Matrix for Area Stability about Ground Stability from Earthquake

1.

Geological Information
Rock Structure (

Information Class

)

Andesite, Granite, Diorite, Metamorf, Vulcanic Breccia,
Aglomerate, Sediment Breccia, Conglomerate
b. Sandstone, AndesiteCBasaltic Tuff, Silt Stone, Arkose,
Greywacke, Limestone
a.

c.
2.

d. Clay, Mud, Organic Clay, Peat Moss
a. Flat (0 C 7 %)
b. Sloping – Moderately Steep (7 – 30 %)
c. Steep – Very Steep (30 – 140 %)

Slope ( )

d.
3.

4.

Earthquake Intensity ( )

Geological Structure (

Source:

Silt Sand, Mudstone, M arl, FineCGranide Tuff, Shale

)

Extremely Steep (> 140 %)

Criteria
Score*)

Weight *)

Total
Weight

1
2

12
3

3

9

4

12

1
2
3
4

3
6
9
12

3

MMI

α

Richter

I, ii, iii, iv, v

< 0,05 g

0,30 g

> 6,5

4

20

1
2

4
8

a.
b.

Far from fault zone
Near from fault zone (100 – 1000 m from fault zone)

5
5

4

4
c. At fault zone ( 1000 meter). Buffer analysis
area was used to implement the level of hazardous area in fault map.

Figure 2.15 Map of Distances from Fault

2.5.5

Hazard Analysis: Ground Stability Model

The result for simulating hazard map has the range between 20 C 49 score value
(Figure 2.16), which means for the minimum score reached in score 20, and for
maximum score reached in score 49. The visualization in hazard map show green
color representing high ground stability, and red color representing area with low
ground stability (Figure 2.16).

Based on stability rating in table 2.11, the first result hazard map reCclassified into 3
(three) scenario hazard zone; low stability, medium stability, and high stability
(Figure 2.17). Statistical hazard zone describes the majority level of ground stability
is medium. The second majority of ground stability is high stability, and then the rest
is low stability (Figure 2.18).
30

Figure 2.16 Distribution Ground Stability (Hazard) Map

Figure 2.17 ReCclassification Distribution Ground Stability (Hazard) Map

31

Figure 2.18 Percentage level of ground stability in research area

Those facts describe half area should be considered carefully from earthquake hazard,
especially for low and medium stability area. The explanation is the combination of
earthquake intensity factor and fault impact area causes medium and high value. Most
of the research areas are potential hazardous area, and it is important to get more
attention. The probability loss impact in research area is medium to high, when the
vulnerability aspects haven’t got more attention. With that reality, it can be predicted
where the suitable location which is safe for living and activities.

The point of interest in this research is a very hazardous area which longitudinally
cracked by Opak’s fault. The impact of earthquake in fault line caused heavy damage
for structure in the surface. Closeness to fault line area cannot be avoided although
we have implemented high technology for structure, in the same manner as explained
by Bell (1999). Totally 13% areas are close or get high impact from fault line, and in
fact that area is majority classified into settlement area (Figure 2.20). Illustration in
Figure 2.19 shows the distribution of settlement areas in fault line located in Pleret,
Jetis, and Imogiri. In those areas there are lots of house buildings and built up
environment (road, drainage, etc.).

The proportion analysis for hazard level in every sub districts shows overall ranking
for hazard level. To identify the hazardous area, we started from areas which have
low ground stability. Imogiri, Pleret, Pundong, Piyungan, Kretek, Srandakan, Dlingo,

32

Banguntapan, Sedayu, Pandak, and Bambanglipuro are classified into potential
hazardous area (Figure 2.20).

Figure 2.19 Area where is in place fault line (area insert in double red line)

Especially in Imogiri, Pleret, Pundong, Kretek, Piyungan, they have low ground
stability more than 20 percent (Figure 2.20). The close factor from fault line, steep
area, and high earthquake intensity caused the high total score.

The second hazardous areas are located and distributed in almost whole Bantul area.
The most area which covered by medium ground stability are Bambanglipuro,
Pandak, Bantul, Srandakan, Sanden, Jetis, Pajangan, and Pundong. Those areas have
medium stability area percentage of over 50% and may even exist over 90%. The
medium ground stability area means that area has less ground stability, or it cannot be
defined as permanent stable area.

Comparing two areas such as Imogiri and Bantul, it determines that Bantul is not
really safe area. The difference of those two areas is Bantul is situated for away from
fault line, but in the level of earthquake the intensity is the same or the earthquake

33

probability for both areas are same (figure 2.14). Bantul also has almost flat
topography while Imogiri has a very steep topography. Physical characteristic of
Bantul is also similar with Pandak and Bambanglipuro which are located in flat
topography but it has high earthquake intensity.

Bambanglipuro, Pandak, Bantul, and others area, which are located in MMI VIII,
zone historically have earthquake occurred in previously. Refers to table 2.4, the

,- .+/

0 1

damage effect in MMI scale VIII can cause totally damage for masonry.

%

%$
(

&

!

"

'

$

"

$

"

"

$

"

#
$&
$!

%

%

'

%$

%

&

&

!
#$

"
!

&

!

% ) " *+, -+

Figure 2.20 Proportion Ground Stability in Every Districts

The high stability area in research study is represented by district such as Sewon,
Kasihan, Banguntapan, Sedayu, and Dlingo (Figure 2.20). Those areas have over
50% which classified into stable area. The affecting factors relates to stability areas
are the physical characteristic areas which haven’t fault line, flat topography, and the
compactness of rock structure. Several areas should get attention although classified
into stable area. For example, Dlingo, Piyungan, Pajangan, and Pleret also have low
34

stability area. The level of earthquake intensity for stable area is still classified in
dangerous situation; in level V to VI MMI can be felt by all and low to medium
potential damage for structure and built up environment.

2.5.6

Comparative Model of Hazard with the Facts on The ground

Although several locations such as Sewon, Kasihan, and Banguntapan are classified
into high stability, they are not totally free from earthquake impact. The previous
earthquake research and evidence shown in Bantul and whole Jogjakarta Province are
susceptible from earthquake hazard. That fact can be described in preCassessment
damage area developed by United Nations Institute for Training and Research
(UNITAR) in 2006, which the damage impact of earthquake was distributed in
random (Figure 2.21).

Figure 2.21 Map of Pre Assessment Damage Area by UNITAR Overlay with Hazard Map

35

The figure 2.21 shows the location of damage in the event of an earthquake in 2006.
Survey conducted at some point the damage location and damage pattern looks great
in the location near the fault in particular. District of Jetis, which located near fault
has experienced of most damage area. Level of damaged started from limited level
into extensive level. Another district which has damaged area was Pleret, Piyungan,
Pundong, Imogiri, Bantul, Pundong, Sewon, and Bambanglipuro. District of Pleret,
Sewon, and Imogiri has similar level of damaged area, which consist for all level of
damaged.

The location of damaged area was majority classified into medium and low stability
area. District of Jetis, Pleret, Imogiri, Piyungan, Pundong and Banguntapan has low
stability area which influenced from fault line location. The conditions exacerbated
by the number of activities centered in the area, for example District of