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RADIUS: A METHODOLOGY FOR EARTHQUAKE HAZARD

ASSESSMENT IN URBAN AREAS IN A GIS ENVIRONMENT,CASE STUDY DEHRADUN MUNICIPAL AREA

Sandeep Maithani

Scientist, Human Settlement Analysis Group, Indian Institute of Remote Sensing,

B.S. Sokhi

Head, Human Settlement Analysis Group, Indian Institute of Remote Sensing,

I T P IJOURNAL

www.itpindia.org

ITPI JOURNAL1 : 3 (2004) 55-64

ABSTRACT

The first step in ensuring the safety of cities against natural hazard like earthquake is to have an understanding of the susceptibilityof areas under consideration, but most of the earthquake damage estimation methods are complex and require extensive data andskilled professionals.The aim of this study is to demonstrate the use of RADIUS methodology in a GIS environment as a simple easy-

to-use tool that can be used by Urban Planners to understand the seismicvulnerability of cities and start preparedness programmesand mitigation measures for better management of future earthquake disasters.

1.0 INTRODUCTION

India, a developing country is undergoing population

growth at an alarming rate, as more and more people

are being attracted from rural to urban areas. In wake

of urbanization most of the cities are expanding

rapidly in an uncontrolled manner and it is getting

very difficult to guide the development in a planned

way. At the same time, since last few years the

seismic activity in India have also gone up resultingin loss of human life and damage to structures as

evident from Gujarat , Uttarkashi, Chamoli and Latur

earthquakes. The seismic risk is high in the urban

areas as most of the building stock is quite old and

also in the construction of new buildings engineering

codes and practices are not strictly followed, as a

result the new buildings are unable to withstand

earthquake forces, as was seen in the recent Gujarat

earthquake. Because of unregulated urban growth

the people are settling in hazardous areas.

Concentration of people and buildings have even

increased in smaller pockets of land.

Earthquake is a natural disaster, but unlike other

natural disasters like floods, cyclones, droughts,

etc., it is not yet scientifically possible to predict the

exact location, time and magnitude of a possible

earthquake. The state of the science today can locate

critical areas, can keep all parameters closely

watched and give a fair indication of what could

happen if earthquake occurs, but in India even the

estimation of probable damage is not worked out.

The primary need now, is to develop tools and

methodology, so that the local authorities can assess

the vulnerability of their cities, assess the extent of

damage which would be caused by an earthquake

and then develop mitigation measures to be taken.

This study aims to illustrate in a GIS environment a

seismic risk assessment methodology developed by

the United Nations, named RADIUS (Risk

Assessment tools for Diagnosis of Urban areas

against Seismic Disasters).It is a very simple andeasy tool that can be used by decision makers and

urban planners who want to have an idea of the

damage and human casualities, in case a big

earthquake were to strike a city. An understanding

of the damage can serve as a benchmark for

establishing disaster mitigation guidelines for various

urban areas. The tool aims to be practical, mainly

for promoting awareness of earthquake damage and

risk assessment.

2.0 OBJECTIVES OF THE STUDYi) To demonstrate in a GIS environment the

procedures involved in the implementation of the

RADIUS methodology and its utility to the urban

planners.

ii) To raise the awareness amongst urban planners

about the necessity for looking below the

surface as a part of planning process. The above

methodology can be very useful in prevention,

mitigation and post disaster aid as town

planning plays a enormous role in all the abovementioned three phases.


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3.0 SCOPE OF STUDY

This study aims to facilitate preliminary estimation

of earthquake damage in developing countries by

urban planners and city administrators,so as to raise

awareness of earthquake risks in the cities But thistool cannot be used for accurate engineering analysis.

This study is limited to the municipal area of the city

and only hazard assessment and vulnerability

assessment of residential buildings to damage is

prepared. Other important factors like study of lifeline

damage, their possible impact after a certain disaster

and the economic factors are not considered. Still

the study fulfills its goal of illustrating the procedure

involved in the implementation of the RADIUS

methodology and highlight its utility for the urban

planners.

4.0 ASSUMPTIONS MADE IN THE STUDY

The following assumptions were made in the study

1. The distribution of building types in each ward

was based on the knowledge and experience of

the authors based on field observations.

2. The soil amplification factor was assumed to be

0.7 for the entire study area.

3. The MMI was taken as a continuous scale, (not

rounded off) as the building damage curve was a

continuous curve, and the damages to various

building was interpolated from it.

5.0 STUDY AREA

The Dehradun city is located in the South part of

Dehradun district between 78o00

E to 78

o10

E and

30o15

N to 30

o25

N. Dehradun is the interim capital

of Uttranchal State, besides being the district

headquarters. Its strategic location at the foothills of

the Himalayas and as a gateway to the hills has

made it an important town in India. It has emerged

as the premier business as well as service center

within the hilly region of Uttranchal. A number of civil

and defense institutions of national repute signify itsimportance in the country. The study area consisting

of Dehradun Municipal Board was originally divided

into 34 wards according to the 1991 census data but

in1995, during the preparation of voters list for

Municipal election the wards were revised and reduced

to 33 in number (fig.1). Two intermittent streams

namely Rispana and Bindal River ,on the east and

west respectively mark the physical limit of Dehradun

Municipal area. The area under the Administrative

Fig. 1 : Location of Study Area

Sandeep Maithani / B.S. Sokhi / ITPI Journal 1: 3 (2004) 55-64


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control of Dehradun Municipal board is 2871 ha., with

a population of 2.7 lacs. The major functions of

Dehradun city are administrative, educational,

commercial, defense and tourism.The prestigious

educational and research institutions are situatedoutside the core city. The western side of the city

houses the Cantonment, Oil and Natural Gas

Corporation, Forest Research Institute and Wadia

Institute of Himalayan Geology. The eastern and

northern part of the city are mainly residential. The

southern part of the city is designated as the industrial

area and also houses the Cantonment. The central

part of the city consists of the old area and has a

mixed landuse (commercial with

residences).Dehradun city lies in Zone 5 of the

seismic zoning map of India. And, therefore, is highlyvulnerable to earthquake (Fig.1). Keeping in view that

the town is an important city of Uttranchal state and

growing at a fast rate, there is an urgent need to do

a vulnerability study of the urban area ,and then plan

effective mitigation measures.

6.0 EARTHQUAKE TERMINOLOGY

The earthquake parameters:Earthquake which

has been defined by the user, i.e. the earthquake

parameters are to be defined by the user the

magnitude, depth, epicenter of the earthquake.

Magnitude:Magnitude or Richter Magnitude is the

index measuring the size of the earthquake, in terms

of the energy content in an earthquake. Richter

Magnitude is calculated using standard Wood-

Anderson seismograph. Theoretically speaking, the

maximum earthquake magnitude could be 8.5.

Depth: Depth of earthquake is how deep below the

ground surface the earthquake originated. The point

of origination of an earthquake is called the

hypocenter, while the vertical projection on the ground

surface is called the epicenter.

Distance:In common earthquake parlance, epicenter

distance is referred to as an earthquake distance.

The point of origination of an earthquake is called

the hypocenter, while the vertical projection on the

ground surface is called the epicenter. The distance

from the source to the site is called the hypocenter

distance, and this distance is used for determining

attenuation of earthquake waves.

Attenuation Equation:The earthquake is originateddeep below the ground surface, called a hypocenter.

Due to the scattering and absorption losses in the

rock medium, the amplitude of the earthquake waves

reduces as the waves travel from the hypocenter to

the ground surface. This reduction in earthquake wave

amplitude is characterized by attenuation equations,given by various researchers. Many of the attenuation

equations given by researchers, are earthquake

specific, and region specific. Majority of the widely

used attenuation equations gives the hazard in terms

of PGA. Most attenuation equations use hypocenter

distance for determining hazard at the site, but few

of them also use epicenter distance recently. The

three most popularly attenuation equations Joyner

and Boore (1981), Campbell (1981), Fukushima and

Tanaka (1990) are selected for use in the RADIUS

methodology.

PGA:PGA stands for Peak Ground Acceleration.

PGA represents the ground shaking amplitude in the

unit of acceleration, typically in terms of G

(acceleration due to gravity 9.81 m/sec2), or any

acceleration unit. PGA of earthquakes is measured

using an accelerograph.

MMI: MMI stands for Modified Mercalli Intensity. The

other popular earthquake intensity scales are JMA,

MSK, Rossi-Forrel and Chinese ones, etc. MMI is

one of the most widely accepted and used earthquakedamage estimation scalesignored in this program.

Following is a description of the MMI scale (after

UNESCO Working Group).

Vulnerability / Damage Curve : Vulnerability

Curves depict the relation between damage rate and

seismic hazard (MMI or PGA). The vulnerability

curves for building and lifeline damages are popularly

MMI based. The RADIUS methodology generates

the hazard as PGA, and then transforms the PGA to

MMI, using an empirical conversion relationship givenby Trifunac and Brady (1970). The vulnerability or

damage curve is a matrix of building damage ratios

for building classes versus MMI. For determining

damage ratios for intermediate MMIs a linear

interpolation is performed .An example of vulnerability

curve is shown in graph-1:

7.0 BUILDING CLASSES AS PER RADIUSMETHODOLOGY

The user is expected to enter the building inventory

percentages for building classes in the target region,

which most closely matches to the building classes



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classification of RADIUS methodology as given

below:

RES 1

Informal construction: mainly slums, row housing,

etc., made from unburned bricks, mud mortar, loosely

tied walls and roofs, such as adobe.

RES 2

URM-RC composite construction: sub-standard

construction, not complying with the local codal

provisions. Height up to 3 stories. URM is un-

reinforced brick or stone masonry, while RC is steel

reinforced cement concrete construction.

RES 3

URM-RC composite construction: old, deteriorated

construction, not complying with the latest codal

provisions. Height 4 - 6 stories.

RES 4

Engineered RC construction: newly constructed

multi-storied buildings, for residential and commercial

(shops and offices) purposes.

8.0 METHODOLOGY

The methodology has been briefed in the followingsteps and flow chart :

At the start a scenario earthquake for the area

should be decided about.This involves deciding

about the various parameters of the scenarioearthquake like- its epicenter, magnitude and in

some cases its location.

The PGA values are generated from this scenario

earthquake model. The normal method used to

evaluate the PGA values generated by the

earthquake hazard is to use one of the following

three equations, widely recognized around the

world

Joyner and Boore (1981):

PGA = 10^(0.249*M -Log(D)-0.00255*D-1.02) ; D = (E 2+7.3^2)^0.5

Campbell (1981):

PGA = 0.0185*EXP(1.28*M)*D^(-1.75) ;

D = E+0.147*EXP(0.732*M)

Fukushima and Tanaka (1990):

PGA = (10^(0.41*M -Log 10(R+0.032*10 (0.41*M)

0.0034*R+1.30)/980

Note - E=Epicentral distance;R=Hypo central distance

Graph-1



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This value also depends on the ground conditions

of the area. And thus after modifying it gives us

the Net-PGA values for the study area. The

various factors for different soil types are

tabulated in Table No.1

Damage will be estimated from the hazard map,

which in RADIUS is taken to be the MMI mapresulting from the scenario earthquake. The MMI

map is generated on the basis of the following

relation by Trifunac and Brady (1975)

MMI = (1/0.3)*(Log10(PGA*980) 0.014)

Note : here PGA value is in G.

The hazard map prepared from the above analysisas represented by the various MMI values, is

represented in the form of a direct relationship withthe possible damage to various structures and lifeline

Flow Cart of Methodology for Loss Estimation

facilities, in the RADIUS methodology. So from here

a direct result is obtained in the form of an estimate

of the expected damage to the settlement.

9. PARAMETERS USED IN THE STUDY

STEP 1: Defining the Earthquake scenario

The scenario earthquake generated was same as

that of the Chamoli earthquake that occurred on 29

March 1999. The parameters that were assumed for

the scenario earthquake were (fig2) :

Richter Magnitude= 6.8

Depth of earthquake= 21km.

Epicentral distance= 13 km.

STEP 2: Calculating the Attenuation function

The attenuation function used in the methodology

was Joyner and Boore (1981) (fig3):

PGA=10EXP(0.249*M-Log (D)- 0.00255*D-1.02)

D= (E2+7.32)0.5

A soil amplification function of 0.7 was assumed for

the entire study area

STEP 3: Converting the PGA to Modified

Mercalli Intensity Scale (MMI)

The Peak Ground Acceleration values were converted

to Modified Mercalli Intensity scale using the Trifunac

and Brady (1975) equation (fig4):

MMI=(Log(PGA*980)-0.014)/0.3

S.No. Soil Types Amplification

Factor

1 Unknown 1.00

2 Hard Rock 0.55

3 Soft Rock 0.70

4 Medium Soil 1.00

5 Soft Soil 1.30

Table 1: Amplification factor for different

soil types



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Fig 2 : Distance from Epicentre of Scenario Earthquake

Fig 3 : Peak Ground Acceleration using Joyner and Boore (1981) Attenuation Funtion andAmplification Factor of 0.7



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Fig 4 : Modified Meracalli Intensity Scale Using Trifunac and Brady (1975) Relation

STEP 4: Applying Vulnerability Functions for

Building TypesThe MMI values calculated were used to find the

percentage damage for each building type (fig5,6,7,8)

using Primary Damage curve data based on ATC 25

document. The MMI values were taken as continuous

and the values were interpolated from the damage

curve, to find the percentage damage for each building

type. The results obtained showed the percentage

of buildings of each type damaged wardwise .

STEP 5: Combine Information

The different building types damaged were then

aggregated wardwise to show the percentage of

building damaged in each ward. (fig 9)

10.0 RESULTS

The following results were obtained after doing the

vulnerability for various building types:

1. The old areas like Khurbura, Lakhi Bagh,

Jhandawala were prone to high damage as most

of the building stock in these areas was old, not

complying with the latest code provisions.

2. The slum areas along the Bindal and Rispana

river would be most damaged as the most of theconstruction is informal or sub standard

construction.

3. The newly developed areas of Rajpur road,

Ballupur,Vijay park would be least effected as

these areas have new construction following the

engineering codes.

11.0 CONCLUSIONS

The RADIUS tool may appear quite rough due to its

simplicity of implementation and ease with which it

generates results about a possible earthquakehazard. But these results can be of great importance,

as the planning agencies may better understand

earthquake and the consequences related to it in

case it strikes some urban settlements. The potential

extent of damage and most susceptible points to

destruction in their city are also clearly highlighted

by these tools.

Damage estimation leads to the knowledge and

awareness of the possible hazards related with some

region. And they can be used for educating the people

about such disasters and thus improving the



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Fig 5 : Damage Rate (%) for Res1 Building Class (Ward Wise) Based on ATC 25 Documents




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Fig 9 : Total Building Damaged (%) (Ward Wise)

preparedness to face such disasters. In the mesh

type analysis, which a normal RADIUS tool uses,based on the zoning of various parts of the city, apart

from the damage amount, the weak points which are

most vulnerable, can also be detected. This helps

the administration to better plan the management of

seismic disaster reduction measures; including

preparedness, emergency response activities,

seismic retrofit, recovery actions and policies. In the

developing nations where the urban settlements are

most unplanned and to worsen the situation the funds

available to implement natural hazard reduction

programs are limited, the results produced by the

RADIUS methodology can formulate the basis forsetting rather clearer priorities. And as the

documentation available with the RADIUS tools states

To merely calculate the damage amount is not

the goal of the earthquake damage estimation. This

should instead serve as a starting point for effective

disaster mitigation.

The most important problem that is associated with

the use of RADIUS tool is the poor non-availability of

appropriate data, particularly in the developing

countries. Most of the municipal agencies are either

not prepared to co-ordinate effectively or theinformation available is incomplete or is available in

widely different formats. In the project report for

Bandung city, Indonesia where the RADIUS tool was

used as a case study; also states that the problem

for selecting the vulnerability function came in there

and was handled with the use of ATC-25 (Applied

Technical Council ,U.S.A) technical values. India

should also move forward with studies to formulate

the vulnerability values so as to improve the reliability

and objectivity of disaster planning efforts. With a

wider part of India now being studied for seismic

zonation and cost effective tools like RADIUS is easily

available, we have better chances of improving the

condition of emergency management in our country.

References1) United Nations (1998). Understanding Urban Seismic Risk

Around The World: Radius Project, United Nations,Publication, Switzerland

2) United Nations Disaster Relief Coordinater (1991).Mitigating Natural Disasters-A Manual for Policy Makersand Planners, UNDRO, Geneva.

3) United Nations Disaster Relief Coordinater (1978). DisasterPrevention and Mitigation .Land use Aspects,Volume5.UNDRO, Geneva.

4) United Nations Disaster Relief Coordinater (1977).Composite Vulnerability Analysis.-A methodology andcase study of the Metro Manila Area. UNDRO, Geneva.

9) Westen , Cees Van. (2000). Remote Sensing for NaturalDisaster Management. International Archives of

Photogrammetry and Remote Sensing. Vol XXXIII, Part B7,Amsterdam.
