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FLOOD! Jakarta;as you know it

Natural disaster insuranceand the power of nation

Study of Seismic Hazard and Site Classification Using Probabilistic Approach for Java Island

JAKARTA’s flood mapQUICK RESPONSE

a brief history ofgunungpadang

17th Edition | January - March 2013

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HEADLINEJakarta flooded! Five yearly flood cycles did not fulfill their promise to come in 2012, 5 years after the enormous

flood in 2007. The five-yearly synth was temporarily eased up. Several scientists were happy, especially scientists

who said that the term is unfounded. In the middle of February 2013, Jakarta was stroke by an enormous flood.

The inundated area is not as wide as the 2007 event, but the loss value is not small. Joko Widodo, the Governor,

said that the loss estimation was IDR 20 trillion. Street in front of Hotel Indonesia, Sudirman-Thamrin Street, the

National Monument and the Presidential Palace were inundated. A “small tsunami” was rushed into the UOB

Tower basement, caused 2 death victims and 56 cars were totally drowned in three basement level. . For more than

a week, the Pluit area was inundated. The cause was different! An 'irrational' flood in the center of Jakarta and the

elite residential were caused by broken wall of West Flood Canal in Latuharhari. The overflowing water damaged

the canal wall, cut of the railway right before the Sudirman Station. It was heading to the Bundaran Hotel

Indonesia, to get through the small waterways and ends up at the Pluit Reservoir. The reservoir has changed,

¼ of its area has transformed into illegal residential. The rest of the area has change, the volume of

trashes and the sedimentation level reduced it capacity. The flood water

pump is not able to fight against the increasing water volume. Pluit were

flooded. Nothing is common in Jakarta Flood. Since a long time…

01

CONTENTS

WHAT’S BENEATH GUNUNGPADANG?

25

HOW GOOD ARE OURFLOOD MAPS?

10

ZONE WITH HIGH PGA VALUE

14INSURANCE AND THE POWER OF NATION

22

JAKARTA floodAN EXTRAORDINARY FLOOD

02

For the time being, let's forget the fact that Jakarta is an alluvial area that formed by rivers from mountains in Bogor

area. Also forget the fact that 58% of Jakarta is located under the average sea level (in 1990, it was only 12% of the

total area). Let's also forget the after-flood hustle. We don't need to remember how stupid we were to be fallen into

the same mistakes whenever the rainy season comes. We are Indonesian who easily forgot yet easily got mad. It's a

bad combination.

We could use the province's incapacity in resolving flood

problem (until this writing being written) as an indication that

flood process is not as simple as we imagined. The complexity is

meant to be simplified, including on how to outlook the

problem. Some of them are presumed to be a 'myths' which

creating certain mindset, though with a weak scientific prove.

First of all, it's all about the flood impact. Lately, we only see

flood has only negative effect. As we never know that flood

cannot be and not allowed to be entirely prevented. In its natural

process, flood is necessary for biodiversity, fish stock

availability, and especially for flood-runoff area fertility (FAO,

2005). Knowing the benefits of living near the water, people

tend to built their houses on the flood-runoff area. Yearly flood

of Nil has made its flowing area very lavish to provide living

resouces for the ancient Egypt culture. Flood was considered to

be the God's present, since it was the beginning of their

agriculture life. Same thing happened in Chinese culture that

was appeared from a fertile area between two big rivers, Hwang

Ho and Yang Tse. A normal flood was an important matter for the

monsoon agriculture system in Bangladesh, where the jute

depends on the sediment that was carried by the seasonal flood.

‘Banjir Kiriman’?

The second complexity is the stigmatization called Banjir

Kiriman. There is a common belief that forests can protect or

even reduce flood. In fact, the direct connection between

deforestation and flood still undefined. This uncertainty has a

long history that related to what is called 'the foam theory'.

Though the theory origins still unclear, it was predicted to be

developed by the European forestry expert in the last of 19th

century. This theory is not yet proven; nevertheless some

people were agreed since it is in line with their knowledge and

intuition. Based on this theory, soil, roots and falling leaves in

the complex forests are functioned as giant foam, absorbing the

water along the rainy season and releasing the saved water in

the dry season, when the water is much needed. In some

countries, this theory is strongly embedded in the national

forestry program and policy (FAO, 2005).

The fact is forest has a very limited influence to the flood

event in the downstream area, especially related to a large scale

flood. Forest only has a local scale impact, where it can reduce

the flow velocity caused by its absorbing and saving capacity.

Though in a large scale rain with a long duration, the forest's soil

will be saturated and the water won't be filtered anymore, but it

will flow on the surface as if a bare site. A study in Himalaya

indicates that the forest site absorbing capacity improvement

compared to non-forest site is not enough to give an impact to a

large flood event in the downstream (Gilmour et al. 1987,

Hamilton 1987). So, reforestation is not an answer for flood

prevention, even though there is so many other benefits of it.

Then, isn't forest preventing erosion and sedimentation,

which is one of the main causes of the downstream flood? Forest

is controlling erosion and sedimentation process, but we should

take a note that is not the tree branch that prevents the erosion,

but the lower plant/shrubs and a pile of leaves/ dead woods in

the forest! Wiersum (1985), Hamilton (1987) and Brandt (1988)

prove that the raindrops under the tree branches have a larger

erosion effect, since it is gathering between the leaves and it

bumps to the earth with a larger size and power. It becomes a

serious problem in the plantation area where its surfaces were

cleaned from other vegetation and its humus were taken for

animal feed or disposed to prevent fire.

JAKARTA flood - an extraordinary flood

Regarding the Jakarta flood, we should admited that we

have a limited data, or even a partial attention to put problem in

an ideal portion. We still cannot find a large flood pattern,

though it commonly acknowledges that a large flood is usually

caused by a large climate pattern. As an example, a great flood

happened in the Bangkok metropolitan, which was recorded to

be a routine event in 200 years. The flood was happened when

the forest was still in a good condition and very wide.

To complete our explanation, we will give an illustration

about the Jakarta flood condition in 2002, 2007 and 2010 which

then being compared to the Katulampa Watergate's depth. The

highest record of Katulampa's depth is neither in 2012 nor

2007, but in February 2010 (see figure 1). Do we really know the

big Jakarta Flood in 2010?

Severe Floods and Synoptic Scale Weather

A severe flood event is always started by a large scale

weather phenomenon (figure 2). Tri Wahyu Hadi said that the

Jakarta Flood event in 2002 was affected by the Monsoon

trench movement to the South and the appearance of cyclonic

vortex in Indian Ocean on the Northwest of Jakarta (figure 3).

Joko Nurjanna said that a high rainfall caused a massive flood in

2007 related to the strong Northeast Cold Surge that reaches

Java, interacting with other synoptic scale weather

phenomenon such as Borneo cyclonic vortex. The Cold Surge

also caused flood in Malay Peninsula in the late of December

2006 – middle of January 2007, before the Jakarta massive

Flood in February 2007 (Figure 4). This Borneo Vortex has 1000

km horizontal scale and 3 km vertical scale around the Borneo.

In the beginning of 2013, the Cold Surge Phenomenon was

happened again, triggered a high rainfall that caused flood in

Banten area in January, and in Jakarta in the middle of February,

as show in Figure 5. It is absolutely important to understand

synoptic weather system and its relation with a high rainfall.

The other factor that has a big influence to Jakarta Flood is

the height of the tidal waves in Jakarta Bay. The sea-level rise will

hold the river flow to the sea. As an example, the tidal waves in

Jakarta Bay from the 2002 event can be seen in Table 1.

Other thing that we should give an extra attention is the

land use change for residential area, which is not only

happening in the downstream area. The development of urban

area will change the absorbing capacity of rainwater by the land,

moreover for a big scale of development where the land was

solidified. The land solidification is clearly will cause the

capacity of land water storage smaller and improved surface

flow. This is certainly happen in Jakarta. Emerging economy,

residential, office, highway and other infrastructure

development happens very rapidly. Everything happens

without a strong land use regulation and a bad city drainage

system development. When flood were measured based on

economic loss parameter and not by it physical parameter will

definitely make an impression that flood is getting worse from

time to time.

Figure 1. Jakarta’s Flood Maps in correlation to water level in Bendungan Katulampa. There’s no linear correlation between the severe flood in Jakarta region with the peak of water level in

Katulampa, so the term of ‘Banjir Kiriman’ is not relevant anymore.

January, 30, 2002 : 160 cm | 607.23 m3/s February, 3, 2007 : 240 cm | 629.97 m3/s February, 12, 2010 : cm | 630.05 m3/s250

?

03


After all of it, the parameter for land subsidence and

climate change has not yet included. Land subsidence was

caused by increasing load from buildings above it and

uncontrolled ground water pumping. Climate change has raised

the sea level that cause the river flow won't flow directly to the

sea as before. Other problem related to flood is the sense of

belonging by the people to their city. When Jakarta was

developing into a capital city, a massive migration was occurred

(Figure 6). These people who weren't the locals experienced a

cultural lag, including their bad habits such as littering and

building alongside the river though it's prohibited. It leads to the

vagueness about who is the real citizen of Jakarta. And isn't it

easier to litter outside your own home? This habit still remains

until the present, and it is even getting worse as the number of

citizen is increasing.

Aside it can trigger disturbance to the flow and causing

flood, this habit can also wipe out the positive impacts of flood!

Please observe yourself what kind of fish you can find in

Figure 2. Synoptic-scale circulation pattern that influence cloudness and rainfall in winter-monsoon region. In maritime continent, convection is high correlated to the circulation of land

and see breeze. Increasing of low-level cloudness and rainfall in coastal zone is influenced by Northeast Monsoon timurlaut and cold surges (Johnson and Houze 1987).

04


Figure 3. Cyclonic vortex in Indian Ocean at northwest of Jakarta is related to severe flood in Jakarta, 2002 (Tri, 2008)

Figure 4. Rainfall accumulation a three severe rainfall observation points (in mm); December, 17, 2006, December, 26, 2006 and January, 11, 2007 (Joko Nurjanna, 2012).

Figure 5. Rainfall in the Jakarta region on January 2013 from RADAR observation. Severe rainfall was called as an impact of cold surge (Sijampang, 2013).

05


in Ciliwung. Does the mud carried by the Ciliwung flood were a

fertile soil layer? It is clearly impossible, since it came from

rubbish and waste.

The third complexity is in the flood handling pattern.

Recently, every magnificent flood episode will be a political

issue. It demands the politicians to give a fast answer to this

crisis; they want to overcome it fast, as expected by the public.

Sadly, it is used to be a short term problem solving. Short term

solution always leads to long term problem.

There is an interesting note we can see in the Katulampa

Watergate, Bogor. This Watergate that was established since

1911 is Jakarta's first flood 'barrier'. The Ciliwung downstream

water flow is split into two branches in the Katulampa

embankment. One is Ciliwung River and another one is used for

Kali Baru Timur irrigation. In a normal condition, water will be

flown to Kali Baru Timur irrigation channel, and only one

Watergate of 5 Katulampa draining gate that is used to flown

few part of Ciliwung water flow. Katulampa Watergate holds

the sedimentation from the upstream of Ciliwung. That is the

main problem of Katulampa. From the last observation in

November 2012, the sedimentation that was hold in Katulampa

is in a very bad condition. Practically, people can walk on the

river! Sands and rocks subside up to hundred meters from the

Watergate. No kind of heavy tools (such as backhoe) worsen the

situation, maybe it's because a small access road (only one car

size). Sedimentation, in form of sands and rocks, are pulled out

of the river body by 7 Watergate officers with help from

surrounding neighborhood. It is clearly impossible to expect for

their limited power to finish these problems. So, sedimentation

problem of people of Puncak area won't significantly affect

Ciliwung condition after the Katulampa Watergate. Therefore, it

is irrelevant to keep on blaming the sedimentation caused by

land transformation in the upstream of Ciliwung (see Figure 7).

A historian, Restu Gunawan, excellently recorded the

Jakarta flood management system from 1985 to his book, “the

Failure of Canal System”. He noted down that flood is never

getting away from Jakarta even though canals, drainage,

waterway and shunts have been built since the colonial era.

Table 1. Sea water level at Tanjung Priok on the end of January and beginning of February 2002. The normal sea water level is 170 cm (Nedeco, 2002).

Figure 6. The increasing of population of Jakarta on 1673-1985 (Restu Gunawan, 2010).

06


Kali Cideng has been flooded since a long time ago, and though

flood control water drainage has been built since 1950 the

condition isn't good. In 1950 and 1951, water disposal that was

only focused in Kebayoran Baru caused flood in Senayan. In

1977, Jakarta was flooded and almost 41% of Batavia was

inundated. Since 1970, not only CIliwung but almost every river

was overflowed. The West Flood Canal idea was given by Van

Breen in 1923, though it was implemented 50 years later in

1973. Even though Kalimalang waterway and Manggarai

Watergate were finished in 1919, flood still happened in Jakarta.

Same goes when Cakung and Cengkareng drain were finished in

1980 but Jakarta still flooded.

Jakarta is in dilemmatic condition, when two flood solution

polar seem to be incompetent to be implemented; 'Total Control

Concept (Infrastructure Approach)' and '(Environment

Oriented Concept').

An infrastructure approach is not easy to be done due to its

low monitoring and maintenance. The latest fact is the collapse

of the East Flood Canal in Latuharhari in the middle of February

2013. The water rushed to the Bundaran Hotel Indonesia area,

covering Thamrin-Sudirman Road and its surroundings, caused

a small tsunami in UOB Tower's basement, 2 people were found

death and 56 cars were totally damaged. Then, through small

drainages the water went to Pluit Dam. A bad condition of the

Dam that was caused by the illegal residential has made the

incoming debit flow much larger than its capacity, a submerged

water-pump, the water cannot be pumped to the sea, and Pluit

area was inundated up to 3 meters high for almost 2 weeks.

Nevertheless, an infrastructure approach could be the best

solution for Jakarta's condition. Don't ever expect the riverside

in Jakarta can be easily transformed into green and open field,

though we know that people live along the riverside are the

result of field acclamation with an apathetic bureaucracy.

For the latest condition, please see Pluit Dam. A high

sedimentation rate triggered trivialization in almost quarter of

the dam, and the piling sedimentation has transformed into an

empty field and changed into an illegal residential. When it

happened, do not ever think to move them easily. Social conflict

will easily appear, though they don't have any ownership right

of it. Don't ever think that people live in Jakarta and its

surrounding won't litter to the river. The “Don't Litter to the

River” policy has been socialized through several programs and

campaigns, but it depends on their bad awareness and sense of

belonging. The government back to surender. The Watergate

has changed into a temporary garbage dump. At the Manggarai

Watergate, garbage has been collected everyday with 10

dumptrucks, and even 20 dumptrucks on the peak season.

Since there is a weak scientific eveidence, an environment

oriented approach will also easily lose. They will definitely

propagandizing “Banjir Kiriman” since that is their rationale to

do a greenery program in the upstream area. They often not

consider some facts that show how weak the scientific

eveidence regarding forest effect at the upstream area with the

great flood event at the downstream, as explained on the

beginning of the writing. They also seem not realize that the

stream flown to the river is happened along the river, and not

only from the upstream.

A fanatic approach that presumed one approach is more

important than other is only made flood become unsolvable.

Hence, the awareness of complexity of the disease (Jakarta

flood) is the first step of healing process.

References

CIFOR, FAO. 2005. Forests and Floods- Drowning in fiction or thriving on

facts?: Center for International Forestry Research and Food and Agriculture

Organization of the United Nations

Gunawan, Restu. 2012. Gagalnya Sistem Kanal. Jakarta: Kompas

Hadi, T.W. 2008. Mesoscale NWP Model Intercomparison for The Maritime

Continent : Preliminary Results and Future Plans. Bandung: ITB

Nurjanna, Joko. 2012. Numerical Studies of Heavy Precipitation over West

Java in January–February 2007: Kyoto University

07


Figure 7. A very bad sedimentation at Bendungan Katulampa on November, 8, 2012.

08

NEAR REAL TIME FLOOD MAPPING VIA QUICK RESPONSES OF COMMUNITIESCASE STUDY: jakarta’s flood 2013

The negative impact of disaster risk can be reduced by proper disaster mitigation management. This include all

aspects; the pre-disaster, at the time disaster happen, and the post-disaster. A pre-disaster risk mapping is an

absolute task to do. Flood risk has a very dynamic risk parameter. Hence, a flood risk map made before the flood

happen should be completed with flood distribution map right after the flood occurred (a real-time flood

distribution map).

A real-time flood distribution map is very important to

predict flood risk in the near future. This map could also be used

as reference for emergency response team to make a decision

and to do the necessary efforts. It could be used as a source to

plan both logistic distribution and evacuation route. The flood

map should be built through proper technical process so that

the flood adaptation action could be more precise on target.

The information technology advances have enable

someone to share disaster information fast and accurate. One of

the technologies is Google Crisis Response using the Google

Maps feature. Right after the 2013 Jakarta Flood; people were

using the feature to share information of flood, especially the

water depth information. Those information were collected in a

database accessible for wide society (Figure 1).

The problem is how to get a fast and accurate data of

inundation distribution based on the flood spots information.

Nowadays in Indonesia, many of inundation maps were based

on administrative boundary that are not shown the water limits

and depths as details. One of the fastest and quite

representative methods to define water depth is spatial

interpolated technic with area topographic correction.

Figure 1. Flood information from quick response of community via Google Maps

09

NEAR REAL TIME FLOOD MAPPING VIA QUICK RESPONSES OF COMMUNITIES - CASE STUDY: jakarta’s flood 2013

There are two kinds of data being used, the first one is the

inundation depth and flood location from society response

(Figure 2, left), and the second one is a high resolution DEM

(Digital Elevation Model) (Figure 2, right). Both data are used as

the foundation to define inundation. The tool is GIS (Geographic

Information System) based software.

Spatial interpolation is a t wo dimensional data

reconstruction method in specific range. Why we should use

topography data? We can't directly interpolate inundation

observation point to be a spatial inundation area. For more

detail, see the inundation profile below (Figure 3). As an

example, the inundation in point A is 100 cm and in point B is 80

cm. If we use common spatial interpolation technic, every area

will be inundated (figure 4). The inundation area is going to be

more realistic if we use topography factor in interpolation

process (Figure 3c).

Figure 4 shows inundation spatial interpolation result that

has been corrected with area topography in DKI Jakarta. The

map can be equipped with numerous features, i.e. road, river,

and also area divider with a smaller scale (figure 5) as necessary.

With this map, we can see more detail the inundation's areal and

depth, not only flood affected administrative map.

We should take a note that the accuracy of the map

depends on the number of observation point which is a binding

point resulted from society report regarding the water depth,

will create better inundation interpolation. For that, we need an

active participation from the society in giving location and water

depth report. In the last January 2013 flood case, there is only 73

binding points were resulted. Indeed, the flood report is easier

to be accessed because of the information technology

advancement. As the time goes by, the number of smartphone

users will increase. With the technology development, people

will get more chance to share fast and accurate information

(geolocation), so that the prospect for the inundation

emergency map development will get better.

Figure 2. (left) Flood inundation data (cm) from quick response of community on January, 17, 2013, and (right) DEM (Digital Elevation Model) data of Jakarta region.

Figure 3. (a). Cross section of flood height observation point. (b) Output of flood

point interpolation. (c) Output of flood point interpolation after topographic

correction. Blue color is flood inundation.

10

NEAR REAL TIME FLOOD MAPPING VIA QUICK RESPONSES OF COMMUNITIES - CASE STUDY: jakarta’s flood 2013

However, this process can be considered as one

process in the emergency map making that will be used as a

reference for emergency response team to decide and do

necessary things. Later on, this emergency inundation map will

be refined with a new map that accounted physical and

dynamical process of the water using a more complicated

hydro-dynamic model. Nevertheless, to run such model we

need a great resources in computing and longer running time.

ReferencesBurrough dan Mcdonnell. 1998. Principles Of Geographical Information

Systems: Oxford University Press

Dressler. 2009. Art of Surface Interpolation. Kunštát

Hutchinson, M. F. 1996. A locally adaptive approach to the interpolation of

digital elevation models

Martz dan Garbrecht. 1999. Digital Elevation Model Issues in Water

Resources Modeling. 1999 Esri International User Conference

Figure 4. Flood map and flood height of Jakarta’s Flood on January, 17, 2013 as an output of interpolation that topographically corrected.

Figure 5. Flood map and inundation on smaller scale region. This is the flood map of the

Ciliwung river watershed near Kampung Melayu - Manggarai.

11


The island of Java, within the Indonesian archipelago, sits atop the Eurasian plate, the Australian plate was moved

northward and subducted under the Eurasian plate. Convergence is nearly orthogonal to the trench axis along

south of Java Island. By the chains of disaster caused by the earthquakes, so the study and evaluation about

earthquake hazard and risk is needed. One of the methods to analyze the earthquake risk probability is to begin

with conducting a seismic hazard study.

Java has the largest population among the other islands in

Indonesia, where more than 65% of the population of Indonesia

lives there. In some earthquake catalogs and literatures, there

were many earthquakes that caused damage on the island of

Java, Yogyakarta Earthquake (2006) and tsunami Banyuwangi

(1994), Pangandaran (2007) and Tasikmalaya (2009).

However, intensive research on earthquakes that were

carried out in particular the island of Java is still very rare, thus

causing losses in the financial and structural, and even fatalities.

With a series of catastrophic events caused by earthquakes, it is

necessary to hold the study and evaluation of earthquake

hazards. For analyzing and find out the risk possibility of

seismicity is usually preceded by seismic hazard studies. The

study of seismic risk by making the seismic hazard map needs to

be done as one of the input materials to mitigate earthquake

disasters.

Regional Tectonic Setting And Historical Seismicity

The Tectonics of Java were dominated by northward

subduction by the Australian plate beneath the relatively quiet

Eurasian plate. Movement of the Australian plate is around 6 cm

/ year with a direction close to perpendicular towards the

southern part of the Java Trench. Beneath Java Island, Australian

Plate laid with a depth ranging from 100-200 km below the

southern part and about 600 km on the northern part of Java.

The consequences of this phenomenon manifest itself in the

high number of seismicity and the existence of more than 20

active volcanoes in Java Island.

Historical earthquake record on the paper of Newcomb

and McCan (1987) listed that the central part of south coast of

Java have been hit by earthquake and tsunami on 1840, 1859,

1867, 1875 and 1921.

Research Methodology

Seismic hazard for a specific site consists of determining the

frequency with which an earthquake characteristic (e.g., peak

acceleration) takes on a defined range of values during some

fixed time t in the future (e.g., 50 years). The study of seismic

hazard is practiced by using probabilistic seismic hazard

assessment method using an event based approach. This means

that the ground motions are computed for each event

individually and the results separately aggregated to form

probabilistic estimate.

A core component of any event based analysis is the

generation of a simulated event (or earthquake) catalogue.

The generation of the earthquake catalogue relies upon an

existing model for the seismicity in the region.

The first step in analyzing historical seismicity and creating

a synthetic earthquake catalogue is to define seismic sources.

There are two general types:

- Area sources are area within which future seismicity is

assumed to have distributions of sources properties and

locations of energy release that do not vary in time and

space. The background seismicity in an area are described

by the capacity rate within each sources zone through its

Gutenberg-Richter a and b values.

12


13

- Fault sources are faults or zones for which the tectonic

features causing earthquake have been identified. These

are usually individual faults, but they may be zones

comprising multiple fault or regions of faulting if surface

evidence of these faults is lacking but the faults are

s u s p e c t e d f r o m s e i s m i c i t y p a t t e r n s , t e c t o n i c

interpretations of crustal stress and strain, and other

evidence.

A simulated event is represented by a plane (or rupture) in

3D space that signifies the region where slip has occurred. The

important parameters of a simulated event are its location,

geometry, magnitude and activity (or likelihood

of occurrence). The rupture trace is the surface projection of the

simulated event along the direction of dip.

A 'stratified' Monte-Carlo technique is used to assign the

event magnitudes. The stratified nature of the technique

ensures that the full range of magnitudes is adequately sampled.

The width and length of the rupture and position of the

rupture centroid are computed using empirical based on

moment magnitude of the event. Three scaling rules are

available use the Wells and Coppersmith (1994) empirical

relationship, a modified version of these rules presented by

Mendez, 2002, and scaling laws for stable continental regions

develop by Leonard (2010). The dimensions of the rupture

plane are computed using the Wells and Coppersmith (1994)

scaling laws.

Where rm is the moment magnitude of the rupture event. If the

rupture area is greater than the fault are we force the rupture

area to equal the fault area while still keeping the same

magnitude. We then calculate the rupture width and rupture

length which is solved using the empirical relationship develop

by the Wells and Coppersmith (1994) but forces the rupture

width to be less than or equal to the fault width.

Ground-Motion Prediction Equations (GMPEs) play a key

role in the evaluation of seismic hazard and risk, are used to

describe the variation of the ground-motion parameter of

interest with respect to parameters of the earthquake source,

propagation path and local site conditions, collectively referred

to as seismological parameters.

These equations are obtained from regression analysis on

the recorded or synthetic values of the parameter of interest. In

engineering practice, traditionally, the most desired ground-

motion parameters are Peak Ground Velocity (PGV), Peak

Ground Acceleration (PGA), and 5% damped Pseudo Spectral

Acceleration (PSA or SA) of horizontal components.

Figure 1. Historical earthquake record in Java Island occurred between 1800's to early 1900's. (courtesy of Newcomb & McCan, 1987).


The ground motion equation are as follows :

· Boore et all. (2008), for strike slip crustal fault

· Chiou and Youngs (2008) NGA model

· Campbell (2003), NGA model

· Zhao et all. (2006), for subducting slab

Each of these equations was assigned a weight 0.3 for the

crustal faults, and weights 1.0 for subducting slab.

Near surface geologic conditions underlying a site will

affect ground motion, and defensible PSHA must account for

these conditions. An amplification factor can be used to transfer

the earthquake motion from the bedrock to the Regolith

surface. Recognition of the importance of the ground-motion

amplification from regolith has led to the development of

systematic approaches to mapping seismic site conditions (e.g.,

Park and Elrick, 1998; Wills et al., 2000; Holzer et al.,2005).

Standardized approach for mapping seismic site conditions

is measuring or mapping VS30. Wald Allen (2007) describe a

technique to derive first-order site condition maps directly from

topographic data. For calibration, they use global 30 arc sec

topographic data and VS 30 measurements aggregated from

several studies in the U.S., as well as in Taiwan, Italy, and

Australia.

This paper present the site classification of island of Java

using shear wave velocity for 30 m depth (Vs30) data from the

USGS.

Model Preparation

We use the catalog of earthquakes Engdhal relocated

hypocentres from the year 1960 - 2009 along Java island, from

1040 to 115.50 longitude and -5.80 to -9.20 latitude. An

earthquake catalogue has been declustered and resulting 1078

independent earthquake events with magnitude above 4.8.

The a and b-value can be calculated by the equations "least

squares linear regression” or with the equation of maximum

likelihood (Aki, 1965; Utsu, 1965; Bender, 1983; Nuannin,

2006).

The validity and accuracy of seismic hazard analysis

crucially depends on the knowledge of the existence and

characteristics of the seismic sources around a particular site

(Sieh and Natawidjaja, 2001). To the advantage of this study,

Java has been being subject research in active tectonic and

earthquake, which has been conducted primarily by the Team-9

of Indonesia Earthquake Mapping. As a result, existences and

characteristics of seismic sources of both the Java fault zone and

the subduction zone are generally well known.

Table 1. Summary of Slope Ranges for NEHRP VS30 Categories

(Wald&Allen,2007)

Figure 2. Soil type map based on velocity sheer speed 30 m (Custom Vs30 Mapping

USGS,2012).

Figure 3. Hypocentre of earthquake catalogue.

14


15

The uncertainty that results from lack of knowledge about

some model or parameter can be reduced, at least conceptually,

by additional data or improved information. The standard way

to depict it in seismic sources and ground motion assumptions is

through a logic tree. Documentation uncertainties with a logic

tree has huge benefit. First and Foremost, the logic tree

organizes one thinking with respect to the uncertain input.

Seconds, it helps in communicating assignments to others.

Result and Discussion

For probabilistic seismic hazard assessment, EQRM

Software was used to calculate peak ground acceleration. The

calculated values for earthquake hazard are displayed as

acceleration contours expected to be exceeded during typical

return period in soil surface. This program is based on the

assumption that the site acceleration has a Poisson distribution

with mean annual rate. It is necessary to draw a number of

hazard maps corresponding to different To and RY in order to

understand the hazard across a spatial region. Traditionally

return periods considered for building design correspond to a

2% and/or 10% probability of exceedance within 50 years. An

exceedance probability of 10% in 50 years equates to a return

period of roughly 500 years and an exceedance probability of

2% in 50 years corresponds to roughly 2500 years.

Probabilistic ground motion analysis were made for sites

located throughout the Java region on a 0.010x0.010 grid.

Figure 3 shows the seismic hazard zones of Java for the return

period 500,1000, and 2500 years based on soil surface.

Conclusions

Generally, the acceleration values in this study are relatively

higher than the PGA maps of Indonesian Seismic Design Code

2010. The increasing of the acceleration values are affected by a

few factors such as different from the traditional approach to

PSHA which integrate over all magnitude and distance

combination, also the estimation PGA reckoned in seismic site

conditions (VS30).

Table 2. Java Fault Zone and their parameters. (Team-9)

Figure 4. Annual Probability of earthquake and from 1960 - 2009 earthquake

catalogue. The red dash line represented Least Squares formula and the green dash

line represented Maximum Likelihood formula. From that graphic solution we've

got b-value = 1.06, a-value = 6.43.

Figure 5. Peak ground acceleration map of Java with return period (a)500, (b)1000,

(c)2500 years.

a

b

c


References

Aki, K. (1965), Maximum lilkelihood estimate of b in the formula logN=a-bM

and its confidence limits, Bull. Earthq. Res. Inst., 43, 237-239.

Biro Pusat Statistik. (2010), Data Penduduk dan Rumah Tinggal.

Boore, D.M., dan G.M. Atkinson. (2008), Ground Motion Prediction

Equations, MEERI, Earthquake Spectra, Vol. 24.

Bender, B. (1983), Maximum likelihood estimation of b values for magnitude

grouped data, Bull. Seismol. Soc. Am., 73(3), 831-851.

Campbell, K. W. (2003), Strong motion attenuation. In W. H. K. Lee, H.

Kanamori, P. C. Jennings and C. Kisslinger (Eds.), International Handbook of

Earthquake and Engineering Seismology, Volume B, Chapter 60, pp.

1003–1012. London: Academic Press.

Chiou, B., dan Youngs, R.R. (2008), NGA Model for Average Horizontal

Component of PGA and Response Spectra, PEER.

CustomVs30Mapping,http://earthquake.usgs.gov/hazards/apps/vs30/cus

tom.php, diakses pada tanggal 1 Maret 2012.

Engdahl, E. R., van der Hilst, R.D. dan Buland, R. (1998), Global teleseismic

earthquake relocation with improved travel times and procedures for depth

determination. Bulletin of the Seismological Society of America, 88, 722-

743.

Gutenberg, B., dan C. Richter (1944), Frequency of earthquakes in California.

Bulletin of the Seismological Society of America, 34, 185-188.

Hamilton, W. (1979), Tectonics of the Indonesia region, U.S Geological

Survey, Prof. Pap. 1078,345 pp.

Holzer, T.L., Padovani, A.C., Bennett, M.J., Noce, T.E., dan Tinsley, J.C.(2005),

Mapping Vs30 site classes: Earthquake Spectra, v. 21, no. 2, p. 353–370.

Meilano, I., Hasanuddin, A.Z., Andreas, H., Gumilar, I., Sarsito,

D., Hanifa,R., Rino., Harjono, H., Kato, T., Kimata, F., dan Fukuda,

Y. (2012), Slip Rate Estimation of the Lembang Fault West Java

from Geodetic Observation, Journal of Disaster Research Vol.7

No.1.

Kanamori, H. (1981), The nature of seismic patterns before large

earthquakes. In Earthquake Prediction: An International Review (eds.

Simpson, D.W., and Richards, P.G.) (Maurice Ewing Series, vol.4, AGU,

Washington D.C., 1-19.

Karig, D. E., Lawrence, M.B., Moore, G. F. dan Curray, J. R. (1980), Structural

framework of the fore-arc basin, NW Sumatra, J. Geol. Soc. Lodon, 137, 1-15.

Katili, J. A., Sumatra, in Mesozoic-Cenozoic Orogenic Belts, Data for Orogenic

Studies, Specs, Publ, 4, edited A. M. Spencer, pp 317-331

Mcguire, R.K. (2004), Seismic Hazard dan Risk Analysis, EERI, Oakland,

California 94612-1934.

Newcomb dan McCan. (1987), Seismic History and Seismotectonics of the

Sunda Arc. In Special Edition of “Jurnal Geofisika”. Himpunan Ahli Geofisika

Indonesia.

Nuannin, P. (2006), The Potential of b-value Variations as Earthquake

Precursors for Small and Large Events. Digital Comprehensive Summaries of

Uppsala Dissertations from the Faculty of Science and Technology.

Park, S., dan Elrick, S.(1998), Predictions of shear-wave velocities in southern

California using surface geology: Bull. Seism. Soc. Am., v. 88, p. 677–685.

Ringkasan Hasil Studi Tim Revisi Peta Gempa Indonesia, 1 Juli 2010,

Bandung.

Robinson, D., Horspool, N., Ghasemi, H., dan Gray, D. (2012), EQRM:

GeoScience Australia's Earthquake Risk Model, Technical Manual 4.0 - Draft.

Sengara, I.W., Suarjana, M., Beetham, D., Corby, N., Edwards, M., Griffith, M.,

Wehner, M., Weller, R. (2010), The 30TH September 2009 West Sumatra

Earthquake. Geoscience Australia

Sieh, K. dan D.H. Natawidjaja. (2001), The Seismic Threat Posed by Faults in

Sumatra To Singapore and Its Neighbors. The Eight East Asia-Pacific

Conference on Structural Engineering and Construction, Singapore, 5 - 7

Dec. Technical paper in the proceeding of the conference.

Utsu, T. (1965), A method in determining the value of b in a formula logn =a-

bM showing the magnitude frequency for earthquakes. Geophys. Bull.

Hokkaido Univ., 13, 99-103.

Wald, D. J., dan Allen, T. I.(2007), Topographic Slope as a Proxy for Seismic

Site Conditions and Amplification. Bulletin of the Seismological Society of

America, Vol. 97, No 5, pp. 1379 – 1395.

16


17

Wells, D. L. dan Coppersmith, K. J. (1994), New empirical relationship among

magnitude, rupture length, rupture width, rupture area, and surface

displacement. Bulletin of the Seismological Society of America 84 (4),

974–1002.

Wills, C.J., Petersen, M., Bryant, W.A., Reichle, M., Saucedo, G.J., Tan, S., Taylor,

G., dan Treiman, J. (2000), A site-conditions map for California based on

geology and shear-wave velocity: Bull. Seism. Soc. Am., v. 90, no. 6B, p.

S187–S208.

Wyss, M., (1973), Towards a physical understanding of earthquake

frequency distribution. Geophys. J. R. astron. Soc., 31, 341– 359.

Natural disaster insurance and the power of nationDefinition of Disaster

Nine years ago, we came to Banda Aceh, one of devastated

cities by the 9.1 Mw earthquake happened in December 26th

2004 that was followed by a tsunami. The smells of dead bodies

were spreading, and ruins were all around. Not only there, but it

was also found in other cities that were affected by the

earthquake and tsunami. Not less than 13 countries were

affected by the tsunami.

This enormous disaster becomes one of important point for

Indonesia record. The disaster has changed people's point of

view about disaster that were known, but only seen as a fairytale

made by scientists, to be something real and close.

Three years later, Indonesia passed a Disaster Law number

24/2007 which defines a disaster as: “An event or series of

events that threaten and disturb the public living, caused by

nature and/or non-nature factor including human factor,

causing loss of l ife, financial, property damage and

psychological impact”. This is a starting step that shows the

government begins to handle disasters seriously.

Disaster comes from the word “dis” and “astro” in latin. it

means “far from star”. A terrible misfortune in astrology

configuration, where star are seen as a fortune and far from star

interpreted as a misfortune.

In a modern description, not every bad event is a disaster. A

disaster is depends on a scale of the subject. Fire could be a

disaster for the owner, but not in regional scale. The United

Nation in International Agreed Glossary of Basic Term Related

to Disaster Management defines disaster as “a serious

disruption to public function, causing widespread human,

material or environment losses which exceed the ability of the

affected people to cope using its own resources.

Disaster is an interaction between phenomenon with

society resilience to face it. In national scale, disaster is a

disruption that the nation cannot overcome it without any

assistance from outside. That is why disaster events have a

strong relation with nation's resilience. The strong relation

should have been made Indonesia to be more serious in disaster

management, which has been finely begun with the issuance of

Disaster Law No. 24 year 2007.

In the Disaster Law No. 24 year 2007 article no 4, it was

stated that one of the objective of the law is to build public-

private partnership and participation. Disaster management

consists of a very wide aspect starting from pre-disaster,

emergency response, to post-disaster rehabilitation and

reconstruction. In a country, the participation from society

elements will define the success of the disaster mitigation

programs plan. That means the burden is not only on the

government shoulders, but on all parties in the country

including private sector and insurance industry.

Increasing the Disaster Resilience through Insurance

In disaster management, the closest part to insurance is

mitigation phase. Mitigation can be defined as every effort that

to lessen the disaster risk impacts. Mitigation is quite not the

same as the three components in disaster management cycle

(preparedness, response and recovery) which are prepared as a

reaction if a disaster happen or as a response to disaster, hence,

mitigation is aimed to reducing the impact of a disaster.

Reducing the risk aftermath could continuously elaborate

as follows:

1. To minimize the risk possibility.

2. To reduce the risk consequences.

3. To avoid risk.

4. To accept risk.

5. To transfer, share or spread the risk.

Insurance is the common form of the fifth type of

mitigation. There are some experts that are strongly disagree

that insurance is part of mitigation, as basically insurance is only

re-distributing the losses, instead of neither reducing nor

avoiding the risk. Despite all the debate, insurance is no doubt

increase community resilience to disasters

At individual scale, someone who has fire insurance for

their residential got more resistance towards fire disaster. If the

18

Natural disaster insurance and the power of nation

19

burns the house, they would be able to handle it without any

assistance as they got insurance protection for the house. The

impact is clearly decreasing considering the individual capacity

has been increased by insurance. It will be totally different if

happen to one who does not have insurance, family saving will

be eroded to rebuild the house and the family will have to move

to their relative's house. Insurance ownership means the

individual resilience has been improved.

In the meantime, our resilience towards disaster is very low.

Often we found disaster survivors instead of join to help other

victim's they positioned themselves as victims. People's

dependency to government's aid is very high. People who are

not supposed to receive aids are asking for it shamelessly. This

condition were found everywhere in Aceh EQ, Tasikmalaya EQ,

Merapi Eruption, etc.

When a national scale disaster happens (due to covered

peril), insured victims who affected will be able to recover their

financial condition, business and rebuild their house sooner. In

national scale, higher disaster insurance penetration will reduce

the impact in macro. If business recovery can't be done quickly,

most probably the macro economy will be affected, not yet

include social problems such as refugees and unemployment.

We need to heighten disaster insurance penetration, so that

insurance/reinsurance has a significant role in improving the

national resilience towards disaster. Principally, without

sharing or spreading the risk to the insured with enough number

and wide area, frankly the disaster insurers are placing

themselves in very risky condition. Purchase of reinsurance

capacity from overseas might solve this problem in short term,

but without any effort to gradually improve the national

retention together with insurance volume improvement,

insurance industry will be built on a fragile business foundation.

Seeing the national disaster insurance condition today,

improving disaster insurance penetration is a must for

Indonesian Insurance Industry. Huge number of insured with

enough premium accumulation and supported by wide area of

Indonesia, the insurance industry resilience itself will be getting

stronger so it will be able to support national resilience towards

disaster.

Cooperation of all insurance players to disseminate

insurance awareness is needed. “Mari Berasuransi” campaign

that we have been doing is a very good step and there should be

more similar programs with an improvement, so that we can

socialize the insurance ideas that in the end will improve

insurance penetration nationally. Using joint resources to

disseminate insurance education for society is the cheapest way

compared to doing it individually by each company using their

own programs or campaigns.

The problem for insurance socialization is not only in the

society's awareness. We are fully recognized that the economic

condition is also influencing. Micro products modification to be

more acceptable should be part of insurance socialization in

Indonesia. The campaign should also be intensively done.

One of disaster insurance/reinsurance's objectives, not

different than other kinds of insurance, is to improve capacity. It

is not only personal or company capacity, but in the massive

scale it will be a “national capacity” to dealing with disaster.

Thus, disaster insurance penetration improvement is not only a

business goal, but also a moral responsibility for every

insurance practitioner in this country.

REVEALING THE ANCIENT SECRET IN GUNUNGPADANG SITE

From regional Geological point of view in the systematic

geological map of Java Island sheet Cianjur on 1:100,000 scale

by Sudjatmiko, Padang Mountain is located in the Southwest

corner and was drawn as a volcanic and sediment rock, which

consists of tuff breccia, lava, sand rocks, side-to-side andesite

lava and pudding stone.

Padang Mountain Megalithic Prehistory Site which

situated in Karyamukti Village, Campaka Subdistrict in Cianjur

is believed by Archeologists to be the largest megalithic site in

Asia. The site's age is presumed older than Djoser Pyramid in

Saqqara, Egypt. Thus, it still needs maximum research to proof.

This fact has made geologists and archeologists feel unsure

about the shape of the “structure”.

The first record of this site presence was made in 1914 by a

Holland historian, N.J Krom, mentioning the existence of large

square stones with various sizes set in a staircase-steps heading

to the Gede Mountain, covered with thousands column of dark

grey Andesite with a smooth surfaced polygonal dimension.

Geologically, natural process can form a smooth surface

stone column. When a magma stream was frozen, a polygonal

stone column was formed. It also happens to magma that flow

outside the earth surface as lava. When it hardened, the physical

processes will form polygonal columns shaped of cooling

cracks.

Those geological scientists who interested with the

megalithic site are trying to see the inside of Padang Mountain

by implementing a geo-electric method and GPR (Ground

Penetrating Radar). It shows the shape of the buried “structure”.

The curiosity to the object has attracted experts. They continued

to concentrate with Laboratory analysis including petrography

20

REVEALING THE ANCIENT SECRET IN GUNUNGPADANG SITE

analysis and radiocarbon dating. The result of carbon dating of

carbon element on sand sediment (in BATAN) in a depth of 8-10

meters is approximately 13,000 BP. If this calculation analysis

were true, it means the natural sand layer is not that young but

supposed to be more than 1 million years old. So, temporary

conclusion from researchers shows that Padang Mountain is a

blanket covering an ancient punden terrace shaped structure

that buried under by an enormous disaster.

It can't be avoided that this research will raise hard

discussion and even a strange ideas in the middle of a “strange”

country condition, and to proof it needs a comprehensive

researches with huge number of resources and time. This fact

show us that history are never archaic to be learned.

21

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