christchurch earthquake risk assessment stage1 report

7/28/2019 Christchurch Earthquake Risk Assessment Stage1 Report

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Earthquake Risk As

StudyPart 1 - Review of Risk A

Methodologies and Dev

Draft Risk Assessment

for Christchurch

Report No. U04 / 108 : Fin


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Earthquake Hazard and Risk Assessment Pr

Earthquake Risk AssessmPart 1 - Review of Risk Assessme

Methodologies and DevelopmentAssessment Methodology for Ch

Report No. U04 / 108 : Final

Prepared by Opus InternatiWellington Off

P. Brabhaharan, Robert Davey, Level 9, Majes100 Willis Stre

Francis ORiley, and Leonard Wiles Wellington, Ne

Reviewed by Telephone: Facsimile: Dr David Prentice

Report No Date: Reference: Status:


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Earthquake Risk

Contents

Executive Summary...............................................................................................

1 Introduction..................................................................................................

2 Scope of Study .............................................................................................

3 Key Components of Earthquake Risk Assessment and Application

3.1 Objectives ............................................................................................

3.2 Risk Assessment.................................................................................

3.3 Socio-economic Consequences.........................................................

3.4 Outcomes ............................................................................................3.5 Applications........................................................................................

4 Literature Review........................................................................................

4.1 Scope of Review .................................................................................

4.2 General Earthquake Risk Assessment ............................................

4.3 Earthquake Hazards ..........................................................................

4.4 Damage and Loss Modelling ...........................................................4.5 Earthquake Risk Studies Undertaken for Christchurch and Can

4.6 Summary of Literature Review........................................................

5 Inventory Data .............................................................................................

5.1 General Approach..............................................................................

5.2 Buildings .............................................................................................

5.3 Roads ...................................................................................................5.4 Water Supply Networks ...................................................................

5.5 Telecommunications Assets.............................................................

5.6 Electricity Assets ................................................................................

5.7 Demographic Information................................................................

5 8 Geographical Information Systems Data Format


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7.2 Risk Assessment Context ..................................................................7.3 Scenario and Probabilistic Approaches ..........................................

7.4 Spatial Assessment Approach..........................................................

7.5 Modelling Uncertainty......................................................................

7.6 Risk Assessment Model ....................................................................

7.7 Risk Assessment Outputs .................................................................

8 Conclusions..................................................................................................

9 Recommendations.......................................................................................

10 Bibliography ................................................................................................

List of Appendices

Appendix A Mesh Blocks and Statistical Area Units for Christchu

Appendix B Example Risk Assessment Outputs for Lifelines


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Executive Summary

Environment Canterbury (ECan) needs to know the likely impact

major earthquake on Christchurch, to fulfil its hazard miti

management functions. Opus International Consultants

commissioned by ECan to review risk assessment methodologies assessment methodology for Christchurch.

A comprehensive review of literature relating to earthquake ris

completed. Key features of significant relevant literature are presen

Sources of asset data for the study have been explored by contactin

and organisations. This indicates that the information required fo

generally available. The inventory would be collected from a variewould include information on critical facilities.

There is good hazard information available from previous resea

additional microzoning information would need to be derived, in

ground class to modify ground shaking, liquefaction ground d

earthquake scenarios, and slope hazards for the Port Hills. These c

the risk assessment. The tsunami risk could be considered in a sepa

A spatial approach should be used for the risk assessment

information system (GIS) platform, and the results of the study be

accompanying tables and charts, so that the information ca

stakeholders.

A methodology has been developed to undertake an earthqua

Christchurch. The approach has been based on generating risk infobjectives of Environment Canterbury and provides a basis for org

risk management actions.

It is proposed that the risk assessment be carried out for four earth

than using probabilistic uniform hazard levels This would pro


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1 Introduction

Environment Canterbury (ECan) needs to know the likely impact

major earthquake on Christchurch, to fulfil its hazard miti

management functions. ECan considers that the earthquake hazar

available is generally of a standard and scale suitable for an earthqu

The Resource Management Act 1991 (RMA) and more recen

Emergency Management Act 2002 require local authorities to iden

the effects of natural hazards and other technological hazards. A

from earthquakes to Christchurch will assist with the manageme

reduction, readiness, response and recovery planning.

Opus International Consultants Limited (Opus) has been commissi

risk assessment methodologies and develop a draft risk assess

Christchurch as part of the Earthquake Risk Assessment Study: Par

This report presents the results of this study, and recommends a

carrying out a risk assessment for Christchurch.


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Earthquake Risk

2 Scope of Study

The scope of the study required by ECan comprises the following s

1. Describe in detail the key components of earthquake risk ass

and in particular the outputs and their applications.

2. Review in detail the available literature on (any) specific earth

carried out for Canterbury and/or Christchurch, and methoddeveloped in New Zealand and internationally for assessing ea

This review will include:

(a) A description of the approach used to complete the literatu

(b) A full bibliographic reference for each report, paper, m

reviewed.

(c) Details of where each report, paper, map or other publicati

(d) A detailed summary of the relevant details of each

publication.

(e) A discussion on the implications of the literature re

development of an earthquake risk assessment model for C

3. Investigate the source, availability and nature of building (re

commercial), engineering lifeline infrastructure (water supp

electricity distribution and roading only) and demogr

Christchurch, and provide a summary of the information in the

4. Investigate the source, availability and nature of earthquake Canterbury and Christchurch, and provide a summary of

report.

5. Identify (if appropriate), the need for, and nature of, any additi

information and/or investigations for the purpose of better a


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Earthquake Risk

3 Key Components of Earthquake Risk Assessment and Appli

3.1 Objectives

Risk may be defined as the chance of something happening that w

objectives. It is measured in terms of consequences and likelihood [

The objective of an earthquake risk assessment is to quantify the

losses due to future earthquakes (the consequences) and their proba given period (the likelihood).

3.2 Risk Assessment

The basic steps in an earthquake risk assessment are:

Hazard Analysis: Identification of earthquake sources.

Modelling of the occurrence of earthquakes

Estimation of the attenuation of earthquake

sources and the study area.

Evaluation of the site effects of soil am

landslide and surface fault rupture.

Inventory Collection: Identification of infrastructure (buildings

exposed to damage.

Classification of the buildings and lifeli

vulnerability to damage.

Classification of the occupancy of the buildi

Damage Modelling : Modelling of the performance of the in

earthquake shaking and consequent effects s

Development of damage functions (relatio


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These steps are illustrated in Figure 1.


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3.3

Socio-economic Consequences

The social and economic consequences of earthquake damag

However, the assessment of the social and economic effects is more

a well defined process to assess these outcomes. Usually these h

multiplier of the direct losses to indicate an order of magnitude of s

A number of researchers have considered the economic impact of

1995). More research is continuing to assess such effects. For examoutlined a framework for assessing the total economic impa

earthquakes on transportation (bridges only considered), using

They included changes in traffic demand after the earthquake. Ho

of this model for risk assessment of a road network was not demon

al, 2001). The Multi-disciplinary Center for Earthquake Engineerin

the USA has an objective to develop a model for assessing the econ

to transportation networks.Research into the social impacts of earthquakes is currently bein

International Consultants, under a 4 year research programme.

It would be prudent to consider assessment of the socio economic e

a future extension of the earthquake risk assessment.

3.4 Outcomes

The primary outcomes of a risk study are summaries and maps

distribution of damage and casualties. A typical summary for an

overall damage rating, the number of casualties, the number of

damage, timeframe for basic reinstatement and likely repair costs.

Key assets covered by the summaries include:

Commercial, industrial and residential buildings;

Critical facilities including hospitals, police stations and fire sta

Lifelines, including:

El t i l d i ti lif li i l di


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Earthquake Risk

3.5 Applications

The outcomes from a risk assessment study have many application

Such applications may include:

Consider the impact of earthquakes and development of

earthquake risk reduction initiatives (for example Earthquak

development);

Earthquake risk reduction initiatives through a detailed unde

and distribution of damage, critical elements and redundancies

Prioritisation and justification for founding of earthquake ri

understanding of the damage and consequences;

Understand and act on the interdependencies and relation

lifelines and emergency response and recovery;

Emergency response planning by the Civil Defence Emergenc

and Civil Defence Personnel;

Understand the post-earthquake recovery resources requi

understanding of the extent of damage to buildings and other i

lifelines). Such a study was carried out for the Wellington Reg

published in a number of papers presented in Wellington

Challenge of Rebuilding Cities (Earthquake Commission, 1995

An earthquake risk assessment for the Greater Wellington Area wa

Consultancy Services (1995) for the Wellington Regional Counci

used extensively in the understanding of the risks to the region,

development, and planning for emergency preparedness. As illus

provided the basis for understanding the resource requirements

events.

An application of comprehensive assessment of the risk to lifeline

of key roads in the Wellington City Road network and developm

strategy undertaken by Opus International Consultants for W

(Brabhaharan, 2004), and this has provided the framework for p

implementation of key vulnerable roads in the Wellington City sta


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4 Literature Review4.1 Scope of Review

A review has been undertaken of New Zealand and international

risk assessment and of specific earthquake risk assessments carrie

Christchurch. This literature review has involved:

1. A review and collation of earthquake hazard and risk reports h

2. A search of library databases by Opus Information Centre;

3. Sourcing of literature from various sources;

4. Review of information collated.

Search of relevant information for the study was carried out Op

which has access to a variety of databases and search facilities whivariety of papers and reports in journals, conference proceeding

and studies.

The seminal paper Engineering seismic risk analysis by Cornell

the considerable advances that have been made in earthquake r

past two decades. Many thousands of papers and other publicatio

on the subject since that time. This review has therefore been limitthat are particularly relevant to a regional earthquake risk asses

Christchurch.

The review is structured as follows:

General Earthquake Risk Assessment.

Earthquake Hazards.

Damage and Loss Modelling.

Earthquake Risk Studies undertaken for Christchurch and Can

4.2 General Earthquake Risk Assessment


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Figure 2 - Flowchart Showing the Basic Regional Risk Assess

[King and Kiremidjian. 1994]

The data and models that are the fundamental building blocks of re

referred to in Figure 2 are:

Models


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Inventory Data

Facility (building, lifelines) structural characteristics

Facility occupancy characteristics

Regional population distribution

The GIS mapping process for the seismic risk analysis is illustrated

Figure 3 - GIS Mapping Process for Regional Seismic Ris

[King and Kiremidjian, 1994]

Maps representing regional geological and geographical data

attributes are combined to produce intermediate maps of regional

hazard maps are then overlaid and combined with structural inve

d l d d b b


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Use of the methodology will generate an estimate of the consequen

a "scenario earthquake", i.e., an earthquake with a specified magn

resulting "loss estimate" generally will describe the scale and

disruption that may result from a potential earthquake. The follow

obtained:

Quantitative estimates of losses in terms of direct costs for rep

damaged buildings and lifeline system components; direct cost

function (e.g., loss of business revenue, relocation costs); casufrom residences; quantity of debris; and regional economic imp

Functionality losses in terms of loss-of-function and restor

facilities such as hospitals, and components of transportat

systems and simplified analyses of loss-of-system-function fo

and potable water systems.

Extent of induced hazards in terms of fire ignitions and fire spre

and building value due to potential flooding and locations of h

To generate this information, the methodology includes:

Classification systems used in assembling inventory and comp

building stock, the components of highway and utility lifeline

economic data.

Methods for evaluating damage and calculating various losses

Databases containing information used as default (built-in) dat

calculation of losses.

A flow chart illustrating this methodology is shown in Figure 4.

These systems, methods, and data have been coded into user-frien

GIS platform. GIS technology facilitates the manipulation of d

population, and the regional economy. The software can be run

platforms, MapInfo and ArcView. The software makes use

di l i d i l ti i t d it l


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8. L

U

Sy

4. Ground Motion 4. Ground Failure

Direct PhysicalDamage

6. Essential and

High Potential

Loss Facilities

12. Debris10. Fire 14. Sh9. Inundation 11. HazMat

16. Indirect

EconomicLosses

Potential Earth Science Hazards

Induced Physical

Damage

7. Lifelines-

Transportation

Systems

5. General

Building

Stock

13. Casualities


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In a simplified form, the steps in applying the methodology are:

Select the area to be studied. This may be a city, a county or a

It is generally desirable to select an area that is under the jur

regional planning group.

Specify the magnitude and location of the scenario earthqu

scenario earthquake, consideration should be given to the pote

Provide additional information describing local soil and g

available.

Using formulas embedded in HAZUS, probability distribut

damage to different classes of buildings, facilities, and lifeline

loss-of-function estimates are made.

The damage and functionality information is used to compeconomic loss, casualties and shelter needs. In addition, the in

on the regional economy are estimated for the years following t

An estimate of the number of ignitions and the extent of fire s

amount and type of debris is estimated. If an inundation map

flooding can also be estimated.

The user plays a major role in selecting the scope and nature

estimation study. A variety of maps can be generated for visua

losses. Numerical results may be examined at the level of the cen

statistical area unit / mesh block in New Zealand) or may be ag

region.

McGuire, RK (2004). Seismic Hazard and Risk Analysis.

McGuire is one of the pioneers of seismic risk analysis, and his

general introduction to methods of seismic hazard and risk analy

attention to one of the most important aspects of seismic risk analy

with the associated large uncertainties. There are two types of unce


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McGuire describes risk analysis methodologies that include all

based on probability theory. The probabilistic seismic hazard asse

is described, along with methods to convert seismic hazard into seis

4.3 Earthquake Hazards

4.3.1 General Approaches

Reiter, Leon (1990). Earthquake Hazard Analysis.

Reiter provides an introduction to the subject of identification of

modelling of the occurrence of earthquakes on these sources.

Models for the occurrence of future earthquakes are based on hist

geology and tectonic processes. There are two sources of earthquak

1. Area sources are geographical areas within which an earthquais equally likely to occur at any time or location, where the l

that cause the earthquakes have not been identified.

2. Fault sources are usually individual faults where the tectonic

causing earthquakes have been identified.

4.3.2 New Zealand DataActive fault and historic earthquake data for New Zealand are av

databases.

Environment Canterbury Active Faults Database

http://www.ecan.govt.nz/EcanGIS/ecanpro/viewer.htm

The Environment Canterbury database keeps an up to date record Canterbury Region.

Active Faults Database of New Zealand.

htt // i / t /d t b /i d b ht l#F lt


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The National Earthquake Information Database is maintained by th

and Nuclear Sciences. It contains summary information of Ne

including epicentres, depths, magnitudes, and felt information

earthquakes. This includes pre-instrumental shocks, but not all inf

all events. The database also contains over 1,000,000 analogue a

recorded by the short-period National Seismograph Network, of w

is held on-line.

Institute of Geological & Nuclear Sciences (2000). Probabilistic SeismNew Zealand: New Active Fault Data, Seismicity Data, Attenuation Rela

This report provides details of the fault sources and area source

probabilistic seismic hazard analysis (PSHA) for New Zealand.

Seismological Society of America (1997). Seismological Research Le

Attenuation relationships are used to calculate the ground shakearthquake location and magnitude. They are derived from recor

motions. This publication provides a good state-of-the-art summar

these relationships.

McVerry GH, et al. (2000). Crustal and Subduction Zone Attenuation R

Earthquakes.

McVerry et al developed attenuation relationships from a da

earthquake records, supplemented by overseas data. The attenuat

of different tectonic types of earthquake (crustal and subduction z

depths. The attenuation expressions for crustal earthquakes have

different types of fault rupture (strike-slip, normal, oblique rev

model takes account of site soil amplification through a range

ground motions are given in terms of peak ground accelerati

acceleration.

Dowrick D.J., Rhoades D.A. (1999).Attenuation of Modified Mercalli

Earthquakes.


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4.4 Damage and Loss Modelling

4.4.1 General

Rojahn, C and Sharpe, R L (1985). Earthquake Damage Evaluation Dat

In the mid-1980s, the US Federal Emergency Management Agenc

comprehensive programme to estimate the economic impacts

earthquake. This included estimates of damages to all types of losses and casualties. Because the required earthquake damage

available in the literature, FEMA and Applied Technology Counci

best way to develop the required data was to draw on the exper

seasoned earthquake engineers. Accordingly a panel of seni

earthquake engineering was established to develop consensus dam

The expert panel estimated the probability of damage to a range

standard damage descriptions used and the associated damage

Table 1. The damage factor (also commonly known as damage rati

of repairing the damage to cost of replacing the structure.

Table 1 - ATC-13 Damage States and Damage Factors (Rojah

The outputs of the ATC-13 study included damage probability m

which is shown in Table 2. By using such matrices, it is possible to

of a structure being in a particular damage state for a given MMI gr

and to estimate the expected dollar loss by multiplying the damage

b h d l l


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Table 2 - ATC-13 Damage Probability Matrix

FEMA (2001). Earthquake loss estimation methodology, HAZUS99

Damage models are provided in HAZUS for the full range of bu

infrastructure.

In HAZUS, damage models are in the form of lognormal fragility

probability of being in, or exceeding, a damage state for a givparameter (e.g., response spectrum displacement, PGA).

Northridge Earthquake Losses

Studies have been carried out by Mary Comerio and others o

Northridge earthquake 1994 in California, USA. Some of these res

to risk assessment for buildings in Christchurch. These studies a

losses, and are based on insurance claims.

In considering these results for New Zealand, care should be taken

in insurance industry and the types of buildings.


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Slight Structural Damage : Flexural or shear type hairline cra

columns near joints or within joints.

Moderate Structural Damage : Most beams and columns exh

ductile frames some of the frame elements have reached yiel

larger flexural cracks and some concrete spalling. Non-duc

larger shear cracks and spalling.

Extensive Structural Damage : Some of the frame elements havcapacity indicated in ductile frames by large flexural crack

buckled main reinforcement; non-ductile frame elements m

failures or bond failures at reinforcement splices, or broken

reinforcement in columns which may result in partial collapse.

Complete Structural Damage : Structure has collapsed or is

collapse due to brittle failure of non-ductile frame elements o

Approximately 20% (low-rise), 15% ( mid-rise) or 10% (high-

the building with complete damage is expected to have collaps


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The estimated damage (i.e., damage state for model building ty

ground shaking) is used in conjunction with other models th

methodology to estimate :

1. casualties due to structural damage, including fatalities;

2. monetary losses due to building damage (i.e. cost of repairin

buildings and their contents);

3. monetary losses resulting from building damage and closubusiness interruption);

4. social impacts (e.g., loss of shelter); and

5. other economic and social impacts.

The building damage predictions may also be used to study expect

given region for different scenario earthquakes (e.g., to identif

building types, or the areas expected to have the most damaged bui

Dowrick, et al. Various

Dowrick and his colleagues have analysed insurance claim record

Bay, 1942 Wairarapa, 1986 Inangahua and 1987 Edgecumbe earthq

They have used the data to calculate the damage ratio as a functio

range of building types and ground conditions. The damage ratioa building divided by the replacement value of the building.

The data from these studies are very important as they provide the

derived information from New Zealand data, as opposed to expert

theoretically (eg HAZUS) derived damage or loss models. Howev

types covered by the data is limited.

Works Consultancy Services (1995). Earthquake Risk Assessment Stud

Opus International Consultants (Works Consultancy Services, 199

and losses to buildings in the Wellington Region, and estimated

selected earthquake scenarios. The methodology that was develope


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cost rates. Drive past surveys were undertaken in a sample of su

QV construction type data. Damages from fire following earthquak

Population data used as a basis of the casualty estimates were obt

of Statistics census data. From this data, it was possible to directly

population in each roll area and the daytime population, for over 1

The under 15years old population was estimated from consi

populations.

A table of casualty rates versus building construction type a

developed from NIBS (1994) and University of Cambridge d

estimating injuries, deaths and entrapments.

The outputs of the studies were:

Numbers of buildings in each damage state (none, ligh

complete).

Costs of repairing earthquake damage to buildings.

Expected damage to critical facilities (hospitals, police stations,

Number of casualties.

Maps showing the geographical distribution of these damages

The results of these studies have been used extensively, and in p

preparedness planning.

One limitation with the methodology used is that it produced nom

of damage and losses, with only a general indication given of the l

mean in any particular event due to uncertainty.

EQC Minerva Model

The Earthquake Commission (EQC) had a computer model de

predict and plan for insurance losses for the portfolio of assets cove


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Estimating Risks from Fire Following Earthquake (2002)

The New Zealand Fire Service commissioned GNS to invest

earthquake fires. A GIS model containing property and valuation

shown to be a useful platform for modelling the spread of post-eart

setting. Two approaches were investigated, one static and on

approach relied on a simple buffering technique to define potentia

sampled randomly to give estimates of losses. Repeated sampling

probability of exceedance of various levels of loss as a function of and the spacing between buildings. The dynamic approach use

technique for determining both the rate and extent of fire spread

range of factors including wind, radiation, sparking, branding, and

of buildings.

4.4.3 Lifelines Studies

Lifelines studies have been carried out in a number of cities and r

starting with Wellington, to consider the potential for damage to

and other hazards, and understand the interdependencies. These

at a high level to understand the potential damage to lifelines larg

judgement of engineering professionals, based on their knowledge.

These include studies for :

Wellington (Centre for Advanced Engineering, 1991)

Christchurch (Centre for Advanced Engineering, 1997)

Auckland

Hawkes Bay

Invercargill

These studies nevertheless provided the impetus for further asse

earthquakes and other natural hazards, and implementation of miti


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American Lifelines Alliance (2001). Seismic Fragility Formulations for

The American Lifelines Alliance has prepared fragility curves for

tanks, tunnels and canals. These are based in part upon a large

damage data that was assembled for that study. These are the m

soundly based models for water systems in particular and pipelines

Data are available from the 1995 Kobe, 1994 Northridge, 1989 Lom

Chubu, 1971 San Fernando and 1906 San Francisco earthquakes pris not a great deal of data available, and even that has inconsis

numbers of repairs and the demands (PGV and PGD) were recorde

Typically damage survey compilations are performed by third par

water system has been restored. Repair records by field crews

ascertain damage counts. Since the main objective of the repair crew

rapidly as possible, documenting damage is of secondary impo

damage estimates have some inaccuracies, including omitted repair

descriptions, multiple repairs at a single site combined into one re

temporary and permanent repair) to one site counted as two rep

inaccuracy is inherent in all damage surveys, is likely to vary signif

to earthquake, and is impossible to quantify. These uncertainties n

when interpreting the results of loss analyses based on these data.

The fragility curves developed by the American Lifelines Allianconsideration the data and lessons from these earthquake events.

Opus International Consultants (2002). Earthquake Loss Assessme

Wholesale Water Pipelines

A probabilistic assessment was made of the financial loss that t

Council is exposed to from damage to its wholesale water supply p

by an earthquake on the Wellington Fault.

The damage models for the buried pipe were expressed as a repai

pipe, as a function of wave passage (peak ground velocity) or gro

ground deformation). These were derived from the American


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Earthquake Risk

telecommunications network. The workshop also addressed

improve earthquake performance.

Work Consultancy Services (1996) Estimated Earthquake Damage t

Outside Plant

Opus (Works Consultancy Services) estimated the damage to the

telecommunications network in the Wellington Region. These

models for buried and pole mounted cables that were developed frdata.

The damage assessment for the telecommunication cables were

ground shaking from earthquakes and more importantly the level

to the earthquakes considered. Permanent ground deformation wa

potential for liquefaction and consequent lateral spreading as well

rupture and earthquake induced slope failures, which were derive

maps and consideration of ground conditions in representative

enabled the assessment of the damage to these assets by developi

relationships.

4.4.6 Road NetworksInternational literature on road risk assessment was summarised

(2001). Relevant and particularly recent literature are summarised

Bridges

The National Institute of Standards and Technology (1992) held a

1991 on earthquake disaster prevention for lifeline systems. The s

lifelines concentrated on bridges, with reports on Caltrans seismic

USA (Maroney and Gates, 1992), and the seismic inspection and st

Japan (Kawashima et al, 1992). There have also been several reporon bridge seismic screening, prioritisation and retrofit.

Transit New Zealand (1998) published a seismic screening proce

bridges based on the methodology developed by Opus Internatio


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Earthquake Risk

Road Network

Nozaki and Sugita (2000) considered the traffic demand from pos

disaster recovery activities and the potential for damage to netwo

network, using a parameter termed structural performance index

of this model to assess the effectiveness of structural (retrofit) an

control) measures. Chunguang and Huiying (2000) presented

reliability of a road network by considering the probability

components of the network using a Monte Carlo simulation. They this approach in considering the location of emergency serv

ambulances.

Henrickson et al (1980) considered losses to users from eart

networks. They assessed a net user benefit or the value of the tr

users as the difference between the total user benefit and the cost

disruption from an earthquake was assessed as a decrease in the tot

Hence the total loss from the earthquake was assessed as :

total loss = repair or replacement cost + loss in user benefits

This together with a component damage probability matrix (earthq

capacity and the associated probability of damage states fo

intensities) was used to derive total cost of earthquake damage. Twith the retrofit cost for that component.

Werner et al (1997) proposed seismic risk analysis of a highway sys

from earthquakes. The use of GIS was suggested, with the followin

System module with network and traffic data.

Hazards module with seismicity, topography and soils data.

Component module with structural, functionality and loss / re

Socio-economic module with loss, emergency response and soc


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Augusti et al (1994) described the use of a dynamic programming

to assess the reliability (that is maintaining connection between evaluate optimal intervention (retrofit of bridges) and reduce the s

networks. The method allowed intervention (retrofit) to be distrib

of total resources, to maximise the reliability.

Opus International Consultants (1999) carried out a risk analys

Councils rural road network comprising the Akatarawa, W

Moonshine Valley areas (Brabhaharan, 2000). A risk managdeveloped for the study based on hazard characterisation, los

economic analysis with the aid of a GIS based model. The stud

hazards, and characterised and mapped the hazards and the poten

The analysis comprised an assessment of the total economic costs, w

total economic costs = damage reinstatement costs + traffic d

The analyses took into consideration the probabilities of various in

In this instance, earthquake and storm hazards were the d

consequent liquefaction, slope failure, erosion and flooding were al

Dalziell et al (1999) carried out a study of the hazards affecting t

Central North Island of New Zealand. They considered the state

area, and assessed the risk to the Desert Road section of State High

traffic analysis using a SATURN model was used to consider thethe road network. The study included consideration of volcanic

snow and ice as well as traffic accidents.

Brabhaharan et al (2001) developed a GIS based approach for the a

road networks and a systematic approach for the management of th

developed by Brabhaharan & Moynihan (2002) who presented met

of risk management in the New Zealand context. This approacapplied to assess the risk to road networks in New Zealand (Brabh

In particular, the application to the Wellington Road Netw

development of systematic risk management and implementation.

The approach developed by Brabhaharan et al (2001) would be


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Christchurch Seismic Loss Study (Soils & Foundations, 1991) pres

potential earthquake losses for Christchurch, based on the understahazard at that time and total building stock values classified into

valuation department. The report estimated an average annual los

dollar values) for structural damage to buildings, with losses excee

dollar values) for a 200-year return period earthquake.

Canterbury Regional Council Infrastructural Assets Risk Assessment (I

Nuclear Sciences, 1994) reported the seismicity, areas of liquefactioCanterbury Region, but did not actually provide an estimate of the

Risks & Realities, a report of the Christchurch Engineering Lifel

Advanced Engineering, 1997) presents a multi-disciplinary approac

lifelines to natural hazards. It presents a qualitative assessment of

drainage, sewer system, water supply, petroleum produc

telecommunications, transport and emergency services. It als

showing the distribution of expected damage. It provides a goo

damage from a variety of hazards, but only in a qualitative manner

Soils & Foundations (1999) Lower Avon River Lateral Spread, Dam

considered the impact of liquefaction and consequent lateral spr

River banks on residential properties, damage costs and potentia

costs. This was an area-specific study confined to a small area of C

LAPP Fund : Earthquake Risk to Councils Assets in Wellington and C

Geological & Nuclear Sciences , 2002) presents an assessment of the

the Council only. The fragility models used for the assessment of th

in the report.

Institute of Geological & Nuclear Sciences (2003). Review of Effect

Differential Settlements on Residential Dwellings in Christchurch. The report by Kirsti Maria Carr on the potential damage to houses due t

Institute of Geological & Nuclear Sciences (2005). Estimated dam

earthquakes affecting Christchurch.


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Earthquake Risk

The available hazard information and the approach for modelling h

detail and discussed in Section 6.

Fragility relationships are available from HAZUS, ATC13 as well a

into New Zealand earthquake damage and selected overseas data s

The Wellington study on 1995 still provides a useful example for a

built infrastructure and casualties. The recent research into damag

earthquake, has been carried out by Victoria University and the I

Nuclear Sciences, and could be useful to better assess the damage fr

Lifelines studies across New Zealand, including the Christchu

Advanced Engineering, 1997) have been high level studies based

have highlighted the importance of earthquake effects.

The American Lifelines Association fragility relations provide a use

of the damage to water supply pipelines, and recent studies

Consultants in Wellington provide an example of its application foare relevant for the Christchurch study.

Schiff AJ (ed)(1998) provides useful information on the assessm

telecommunication systems, and the Works Consultancy Services (

example of risk assessment to Telecom assets in Wellington.

The HAZUS based assessment of the risk to bridges and the Bapproach to assessment of the risk to road networks provide

networks, particularly as illustrated by its successful application

network by Brabhaharan (2004).

Previous risk studies for Christchurch have considered some aspec

the city, but not in a comprehensive manner.


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Earthquake Risk

5 Inventory Data

5.1 General Approach

Research into potential sources, availability and nature of data fo

lifeline assets and demographic information has been carried out fo

ECan limited the lifeline infrastructure investigations to water

telecommunications. Other assets such as the rail network,

infrastructure were not investigated but could be included in the ea

The research was undertaken by contacting infrastructure manag

City Council (CCC), utility and telecommunications companies.

held with people responsible for maintaining and updating

organisations.

The information available is predominantly stored in databas

management plans and seismic investigation reports. Details of t

sections below.

Another key source of information is the engineering lifelines stud

was undertaken in the mid nineties. The results are summarised i

and Realities (Centre for Advanced Engineering, 1997). This st

collation of lifeline information that was provided by various o

suitable for risk assessments.

5.2 Buildings

The CCC and commercial organisations such as Quotable Value (Q

properties and buildings. The council databases have been popu

from:

Building permits prior to 1992;

Building consent information since 1992;

Property information supplied by the former Government Valu


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Earthquake Risk

Typical property information that is available from commercia

include :

Residential/commercial/industrial classification;

Building Age (decade of construction);

Wall construction material (wood, brick, concrete etc);

Property use (residential, office, hotel, retail, mixed, storage, ed

Numbers of properties;

Land and building valuations.

The three important factors for classifying the earthquake performa

building structure,

age, and

number of storeys.

The age and number of storeys can be readily obtained from

databases, however the building structure classification (i.e. unre

frame, concrete frame) is not generally held on any databasclassification and age of the building can be used to infer the likely

reasonable accuracy. A small random sample of commercial prope

to verify the validity of the assumptions.

CCC has a register of earthquake risk buildings. The data is stored

used to prepare LIM reports. The council could supply a spreadsh

identifier.

Information on seismic upgrades to commercial buildings is not a

databases. Seismic strengthening of earthquake prone buildings

the structural performance of a building in a seismic event, above

th b ildi l ifi ti l


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Earthquake Risk

and GIS layers. Some costs may apply to CCC staff that spend tim

requests and processing data to provide it in a suitable format foinformation may already be held by Environment Canterbury, who

for the study.

Alternatively, property information can be obtained from a comm

as QV. QV hold similar information to the council databases (w

earthquake prone building register). The benefits of using QV ar

the information in a timely manner and reduce the negotiations andobtain data from the CCC.

5.3 Roads

5.3.1 Local Roads

The road network model can be developed from one of the followin

Topovector data;

RAMM database.

Use of Topovector data requires a software licence. The Topovect

entire road network in the Christchurch City to be modelled in GIS

on 1:50,000 topographic maps. However, the attributes associated

and include such characteristics as the number of road lanes andsealed or unsealed.

RAMM data could be sourced from the CCC. The RAMM data ha

can be exported into other GIS systems. The RAMM data con

characterise the road including surface width, seal type, traffic vo

history.

The RAMM data has several advantages over the Topovector data

the results from the analysis, in the form of GIS layers, can be retur

own use at a later date, and would be consistent with the data alrea

Another advantage is that the RAMM data contains more attribute


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Earthquake Risk

5.3.2 State Highways

State highways 1, 73, 74 and 75 pass through the Christchurch city

owned and maintained by Transit New Zealand (Transit).

The RAMM database is used to store information on the hig

attributes can be exported into a GIS system with RAMM mapping

Bridge information is held on a separate database. For Transit,

seismic screening of the state highway bridges in the Christchurch

this study would be available for the Christchurch risk study.

5.4 Water Supply Networks

The key assets for the water supply network are pipes, pumpi

reservoirs. The CCC stores information on pipes in a GIS system. P

size, length, age and material are also available. The location of pvalves and reservoirs can also be linked into a GIS model.

An overview of the Water Supply Asset Management Plan 2002 is

website. A detailed copy of the asset management and business c

be made available to the risk study group.

5.5 Telecommunications Assets

Telecom New Zealand Ltd (Telecom) and Telstra Clear L

communication networks in Christchurch. Vodafone and

independent cellular phone networks.

5.5.1 Telecom

Telecom uses Small World GIS software to store information o

Telecoms main assets are exchange buildings, underground com

cell phone towers.

Telecom has a policy of not releasing drawings showing the comp

network as this information is commercially sensitive Telecom ha


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Earthquake Risk

Any network information used in the risk study would need prior s

5.5.2 TelstraClear

The majority of the TelstraClear network has been installed over

majority of communications equipment is likely to be restrained wi

exchange buildings designed to modern standards.

Information on the TelstraClear network is stored on a GIS sys

indicated they would be willing to provide information with a

agreement. Exchange buildings, cabinets and major underground

able to be incorporated into a GIS model.

TelstraClear have also provided a summary document of a recent c

includes information on major cable routes, exchange buildings, vu

other providers such as Vodafone and BCL.

5.5.3 Vodafone

Vodafones main assets include cellular towers and small exc

majority of the Vodafone network has been installed over the las

most of the network has be designed to modern seismic standards.

The tower structures are not susceptible to seismic loading.

foundations will be susceptible to earthquake induced ground setUnderground fibre optic cables are also prone to damage from earth

Vodafone exchange buildings are generally small single

communication cabinets. Most cabinets are generally secured by s

designed to the latest earthquake standards.

5.6 Electricity Assets

Orion NZ Ltd (Orion) owns and operates the local supply netw

region.

Orion receives power via the national grid which is owned and o


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Earthquake Risk

substations have switching cabinets housed in buildings and switch

voltage equipment such as circuit breakers and transformers.

The transmission and communication tower foundations are su

induced ground settlement and landslides. Earthquake induced

lines located away from Christchurch city area that are closer to th

may affect the power supply to Christchurch city. This risk stud

key electricity supply assets within the Christchurch city area.

5.6.2 Local Supply Network

Orions main assets are district substations and supply cables.

switching cabinets housed in buildings and switchyards that

equipment such as circuit breakers and transformers. The electrici

city are a mixture of overhead lines and underground cables.

Orion has a GIS system that holds information on the electricity net

A copy of the 2005 asset management plan is available on the O

management plan has a section on risk management that summaris

Seismic strengthening of substation buildings;

Importance of electricity supply to other lifeline services;

Key assets that could lead to catastrophic supply failure;

Recent earthquake mitigation works.

Orion has provided a summary of reports relating to recent seism

selection of which are listed below). The reports would be made av

group.

Resource Management Act - Risk Assessment, 1993;

Resource Management Act Reduction of Risk Exposure, 1993

O d P d M d T f S 1998


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Earthquake Risk

5.7 Demographic Information

Demographic information is available from the Statistics New Zea

Information that will be useful in a risk analysis study includes:

Average number of people per household (night time figures o

Average number of people employed in the Christchurch Cent

The census data can be grouped into appropriate land areas such aor mesh block. The mesh block is the smallest unit of area for w

available.

5.8 Geographical Information Systems Data Format

Property information is stored in the CCC GIS databases in two for

parcels are stored in a polygon theme/layer with each having a ke

Secondly the addresses of properties are stored in a point theme/la

Non-spatial data covering the items of interest to the CCC are a

databases. These contain data such as capital values but not n

condition, age or materials. Any of this non-spatial data can be

parcels polygon theme/layer through the common key field landp

Actual building outlines are also stored in the CCC GIS databases fields or useful attributes. The building centroids could be used to

data to a more refined location to that of the parcel centroid.

Water, wastewater and stormwater are stored in line theme/lay

such as pipe age, material, and diameter.

The information can be readily incorporated with other GIS them

basis for further data manipulation and spatial analysis. The result

the data provides a basis for the risk/hazard analysis.

Much of this information is also held by Environment Canterbury

parcel data) or for restricted use in the consents section (water, w


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Earthquake Risk

The power supply companies have shown a willingness to supply i

Telecom New Zealand has indicated that they would make inform

would be limited for commercial sensitivity reasons. The informat

make available for the study needs to be confirmed. TelstraCl

would provide the information.

Information on water supply would be available from CCC and the

on local roads. The information on state highways is available from

h k k


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Earthquake Risk

6 Earthquake Hazard Information Review

6.1 Introduction

The source, availability and nature of earthquake hazard informati

to assess the appropriateness for use in the earthquake risk study.

A comprehensive list of earthquake hazard information held by

relevant publications have been obtained and used in this revi

earthquake hazard in Christchurch has also been sourced and revie

6.2 Earthquake Hazard Literature

6.2.1 Ground ShakingThe Earthquake Hazard in Christchurch (Elder et al, 1991) presented

the earthquake hazards in Christchurch, and contributed to a sigknowledge of the earthquake hazards in the city. It considered ear

prediction of the intensity of ground shaking (with associated prob

intervals) and spectra. In addition, it also considered the influen

area, the potential for amplification of shaking, liquefaction suscep

induced slope failures. It also presented some generic comments

to buildings and infrastructure. However, this did not provide a f

risk.

Natural Hazards in Canterbury (Canterbury Regional Council, 199

hazards affecting Canterbury. A section of the report present

including historical earthquakes, the faults systems capable of cau

summary of the outcomes of seismic hazards assessments.

Risks & Realities, a report of the Christchurch Engineering Lifel

Advanced Engineering, 1997) presents a multi-disciplinary approaclifelines to natural hazards. This comprehensive report only pro

earthquake hazards affecting Christchurch.

The report notes that the likelihood of surface fault rupture in Chri

E th k Ri k


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Earthquake Risk

The first two scenarios were considered to be capable of causing

intensities on the Modified Mercalli Scale, and the third MM VIIstudy adopted a 150-year return period earthquake with shaking i

IX over most of Christchurch. There was disagreement betwee

expected intensity of shaking in a 150-year return period earthqu

considered to be of less significance in the assessment of damage to

The report notes the potential effect of the deep relatively soft sedi

the soil profile on the ground shaking, and points out that the shakincreased by 0 to 2 MMI units compared to bedrock, or 0 to 1 M

average ground (shallow soil). The potential for ground shaking a

into three zones (Zone 1 bedrock at shallow depths, Zone 2 se

deep and Zone 3 sediments 50 m to 800 m deep).

The Probability and Consequences of the Next Alpine Fault Earthqu

presented the outcomes of further paleoseismic investigations and

forests along the Alpine Fault corridor in the West Coast of the S

concluded that the last two earthquakes along the Alpine Fault app

about 1717 AD and 1620 AD. Based on the information available in

Yetton et al (1998) estimated the probability of an earthquake in

Alpine fault over the next 50 years to be 65 15%, and 85 10% ove

Earthquake Source Identification and Characterisation (Pettinga et

presented the potential earthquake source information relevant to This collective study by the University of Canterbury, Geotech Con

Institute of Geological & Nuclear Sciences, presents the location

known faults in and around the Canterbury Region, classified into e

The report notes that while instrumentally recorded seismicity b

Plains indicates active earth deformation, and the highest recorded

to 8 in Christchurch was recorded during the 1869 New Brightoinferred epicentre immediately offshore from Christchurch), there

sources of earthquake in the Canterbury Plains including Ch

alluvium, complex subsurface structures and poor data constra

earthquake sources, and there remains the potential for hidden ea

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Earthquake Risk

follow on study that presented a review of historical earthquak

probabilistic seismic hazard assessment.

Christchurch is noted to have felt MM 6 or greater shaking in nine

and their characteristics are summarised in Table 3 below :

Table 3 Historical Earthquakes Causing MM 6 or Greater in Chr

Year of

Occurrence

Earthquake

Name Magnitude

Location / Epicentral Dist

from Christchurch

1869 Christchurch 5 ?Very close Addington

hidden source ?

1870 5.5 ?South of Christchurch, La

Ellesmere ?

1881 Castle Hill 6.0 ? Cass ?

1888 NorthCanterbury 7 7.3 Hope Fault, west of HanmSprings

1901 Cheviot Ms 6.9 Parnassus

1922 Motunau Ms 6.4 Motunau / Scargill

1929 Arthurs Pass Ms 7.01 Kakapo Fault / Arthurs P

1929 Buller Ms 7.8

1994 Arthurs Pass ML 6.7 Arthurs Pass

The report suggests that amplification by about 1 MM unit occurre

five of these earthquakes in the 1881 Castle Hill, 1888 North Can

1929 Arthurs Pass, and 1929 Buller earthquakes.

The probabilistic seismic hazard analysis carried out as part of thmaps of peak ground accelerations on average soil sites (Class

Region, for return periods of 50 years, 150 years, 475 years and 10

for 0.2 s and 1 s spectral accelerations are also included. The p

maps have also been converted into MM intensity maps using an

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Earthquake Risk

It is noted that the Alpine Fault has a very small contributio

acceleration, but makes a significant contribution to the 2 s sChristchurch.

Table 4 Ground Shaking Estimates for Christchurch

Ground Shaking in Christchurch in A

Return PeriodGround Shaking

Parameter50 years 150 years 475 yea

PGA 0.17 0.25 0.37

0.2 s SA 0.37 0.61 0.97

0.5 s SA 0.24 0.35 0.49

1 s SA 0.09 0.16 0.19

2 s SA < 0.05 0.08 0.12

MM I 7.5 7.99 8.52

The expected ground shaking in Christchurch from a local earthquake and an Alpine Fault earthquake are summarised in Tab

Table 5 Expected Ground Shaking in Christchurch from Earthqu

Local earthquakeFoothills earthquake on

Ashley, Springbank, Porters

Pass-Amberley Faults

Magnitude /

distanceM 5 to 5.5 closer than 20 km M 7 to 7.2 closer than 50 km

MM Intensity 7, possibly 8 8

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Earthquake Risk

Deaggregation plots showing the percentage contribution of diffe

to the ground shaking with different return periods in Christchurreport.

The deaggregation plots for peak ground accelerations (PGA) with

return periods (reproduced in Figure 6 and

Figure 7) and 1 second period spectral accelerations for these return

Figure 8 and Figure 9) show the significant contribution of th

(magnitude of about 7 to 7.3) and secondly the local earthquakes (m

peak ground accelerations.

The dominant contribution to higher spectral acceleration motio

from the distant Alpine Fault earthquake (magnitude 8 to 8.5) and t

(magnitude 7 to 7.3)

Figure 6 - Deaggregation Plot, PGA, for 475 year Recurrenc

(Institute of Geological & Nuclear Sciences, 2000)

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Earthquake Risk

Figure 8 - Deaggregation Plot, 1s SA, for 475 year Recurrenc

(Institute of Geological & Nuclear Sciences, 20

Figure 9 - Deaggregation Plot, 1 s SA, for 1000 year Recurrenc

(Institute of Geological & Nuclear Sciences, 20

Environment Canterbury Active Faults Database Manual (Environm

summarises how ECan has compiled and holds information on

Canterbury Region. The information includes the location, activi

intervals, rupture length and displacement and potential magnitudcould be caused by its rupture.

6.2.2 Liquefaction Hazard

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q

Zone 3 into two liquefaction zones, Zone A high susceptibility (san

depth), and Zone B moderate susceptibility (silts and sandy siltdepth or deeper). It appears the liquefaction susceptibility has be

based on soil types rather than the potential for liquefaction a

damage.

Soils & Foundations (1998) carried out a study to assess the potenti

the Kerrs Reach to Pleasant Point section of the Lower Avon Rive

that widespread liquefaction and lateral spreading was likely inFoundations (1999) also considered the impact of liquefaction

spread in the Lower Avon River banks on residential propert

potential liquefaction mitigation costs.

Soils & Foundations (1999b) also assessed the potential for liquefa

Special Planning Zone along the Heathcote River, and conclud

investigated, 5 had a medium to high probability of liquefaction an

moderate earthquake (450 year return period) and an additionaprobability of liquefaction in a large earthquake (1000 year return p

Cassassuce and Berrill (2000) carried out seismic cone tests a

Christchurch and assessed the liquefaction susceptibility at about 2

potential for liquefaction.

Carr (2001) considered different methods of estimation of liquefacand the impact of differential settlements on house designs. The au

7.5 Porters Fault earthquake could lead to liquefaction-induced set

70 mm to 185 mm.

Beca Carter Hollings & Ferner (2003) contacted various organisatio

on ground conditions in the Christchurch area, on behalf of Envir

summarise their findings.

Beca Carter Hollings & Ferner (2004) report on the outcome

Liquefaction Study for Environment Canterbury. Liquefaction ma

groundwater levels, and indicate high, moderate or low liquefacti

on whether liquefaction is likely in 0 12g 0 2g or 0 34g earthquake

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q

Natural Hazards in Canterbury (Canterbury Regional Council,

information on earthquake induced slope failures, and the Canterbury Region. There is limited information relating to Chri

that there is a significant rockfall hazard in the Port Hills, and ther

scale failure in the Port Hills loess.

Risks & Realities (Centre for Advanced Engineering, 1997) presents

hazards and presents slope hazard zones for hill areas, particularly

three hazards zones, 1 low risk, 2 moderate risk and 3 high risdamage could be triggered by a 1 in 100 year storm, or 1 in 100 or 1

occurring in later winter.

6.2.4 Tsunami Hazards

Tsunamis are a series of very long waves caused by a sudden dis

undersea earthquake fault rupture, landslide or volcanic eruption

sea). Earthquake induced tsunamis can be caused by an undconsequent landslide. Tsunamis can be locally generated by s

generated at a distance and travel many hundreds or thousands

coastal areas. The tsunami magnitude could be amplified by the lo

Most tsunami reports for New Zealand have been associated w

tsunamis, and these can reach the Christchurch coastline.

Natural Hazards in Canterbury (Canterbury Regional Council, 1994

on the tsunami hazards in Canterbury and mainly focuses on

originating from the South American coast.

Risks & Realities (Centre for Advanced Engineering, 1997) presents

hazards that could affect Christchurch.

The risk of a near field tsunami from active faults off the Christcunderstood.

Tsunamis can cause catastrophic damage to coastal areas as eviden

Tsunami of 26 December 2004, which caused severe and widespr

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6.3 Discussion of Hazard Information

The probabilistic seismic hazard study for Canterbury (Institute o

Sciences, 1999) and for New Zealand (Institute of Geological &

provide a basis for the risk assessment for Christchurch. There are

results for the two studies in the probabilistic hazards, and this may

discussion with the Institute of Geological & Nuclear Sciences.

However, a scenario approach may be more appropriate for the C

(see discussion in Section 7), in which case the differences would n

study. The Institute of Geological & Nuclear Sciences was asked

further recent developments that would make the Canterbu

Geological & Nuclear Sciences, 1999) out-of-date. It is understoo

comm.) that there are no significant changes to the seismicity an

Hazard Assessment since that time. However, it is understood tha

Poisson distribution for the occurrence of earthquakes, and does n

elapsed time since the last earthquake, which may be significant iFault, where a significant time has elapsed since the last earthq

assessed recurrence interval for that fault. However, this is not lik

difference (


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Ground Shaking

There is good information on the seismicity of the Christchurch a

be useful to develop a ground class map so that changes to the gro

and soil conditions can be assessed. The ground class map can

ground information collated for ECan as part of the liquefaction haz

Liquefaction Hazard

Comprehensive liquefaction hazard maps have been compileEnvironment Canterbury, and would provide the basis for assessi

consequent damage to infrastructure. The liquefaction map

extrapolated for other earthquake scenarios to be considered in the

Earthquake induced Slope Failure

There is limited information on the earthquake induced slop

Christchurch. Given the terrain in Christchurch, the slope failure

confined to local areas, such as Port Hills. It would be prudent to c

map the earthquake induced slope failure hazards in the Port H

earthquake risk assessment study. This can be based on topogra

and reports supplemented by site reconnaissance.

Tsunami

It would be prudent to review the tsunami hazard information com

Civil Defence Emergency Management, and consider what tsun

necessary to assess the risks from tsunami. It is suggested that

study to the proposed earthquake risk study.

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7 Development of Risk Assessment Methodology for Christch

7.1 Objectives

Environment Canterbury needs to know the likely impact and c

earthquake on Christchurch. This will allow it to fulfil its

emergency management functions. The primary purpose of

therefore to provide information on the impact and consequen

Christchurch.

7.2 Risk Assessment Context

The Australian / New Zealand Standard, AS/NZS 4360 : 2

(Standards New Zealand, 2004), defines risk as the chance of som

will have an impact on objectives. The risk is often measured in t

of the consequences of an event and their likelihood. The risk ma

out in the standard and is reproduced in Figure 10.

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In the earthquake risk study context, risk is the damage and oth

built environment, natural environment and on the society inearthquakes. The risk information is required to enable Environm

its hazard mitigation and emergency management functions.

For the earthquake risk study, the consequences are the:

Damage losses (repair or replacement cost)

Consequential direct losses (e.g. traffic disruption)

Indirect social and economic costs

This risk study focuses mainly on the damage losses and some con

The indirect consequences such as economic losses and social dis

difficult to quantify and are not considered in this study. The

considered separately as a follow-on study based on the results o

ongoing research initiatives to develop methodologies to ass

consequences of earthquakes and their impact on the built envir

Section 3.3.

For risk mitigation and emergency management, it is important to k

the damage and losses, and not just the total losses, to facilita

reduction and response. A spatial approach to the risk assessmen

to be more beneficial.

7.3 Scenario and Probabilistic Approaches

Earthquake risk assessments are commonly carried out for selecte

(e.g. Alpine Fault event) or for selected probability levels (uniform

probability in 50 years).

The probabilistic or uniform hazard approach is useful for eco

impacts of earthquake risk and risk mitigation options.

A scenario approach is useful to assess the impact to a city or regio

that emergency response and recovery measures can be planned I

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The scenario approach would also be useful for lifeline asset own

impact to their assets from particular events and the consequentiprovided to the community or customers. This would also allow a

of service or performance criteria and assess whether these would

plausible earthquake scenarios.

However, a probabilistic approach based on a range of uniform e

(say 10% in 50 years) would be useful to assess the financial bene

particular level of performance or for assessing risk reduction mea

assessments carried out for Christchurch have been carried

probabilistic risk assessment approach (Soils & Foundations,

Geological Sciences, 2002), and while they could have been useful

they have not provided the information necessary for Environmen

emergency management functions.

Given that the primary purpose of this risk study is to provide

required for it to fulfil its emergency management and risk reductiapproach is considered to be the most appropriate. This will

owners such as Christchurch City Council, and could be lat

probabilistic risk assessment based on uniform hazard levels if con

separate study using tsunami scenarios should also be considered.

7.4 Spatial Assessment Approach

The asset information should be obtained in spatial format wherev

assessment results presented spatially. The hazard information

and or derived in spatial form. It would be prudent to carry out th

possible using GIS to facilitate risk assessment and presenta

information may be better assessed using a database or spreadshee

would facilitate the use of the results for emergency managem

planning.

It is therefore proposed that GIS be used as the basis for the risk ass

7.5 Modelling Uncertainty

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Given that the uncertainties are significant, it would be prudent

uncertainty through appropriate analysis. The uncertainties wouthrough :

Assigning a range of values for the parameters based on

suitable probability distribution.

Monte Carlo analysis using a program such as the @Risk modu

This would lead to outcomes that are probability distributions o

stated in terms of a mean and confidence intervals.

This would involve assessment using a combination of GIS an

module with Monte Carlo simulation capability such as @Risk.

7.6 Risk Assessment Model

7.6.1 General Description

A potential risk assessment model for the Christchurch Risk S

discussed below. The approach is consistent with that used in H

and other studies undertaken in New Zealand (Works Consulta

Brabhaharan, 2002).

The risk should be quantified by, for example, $ losses (cost of r

breaks and number of casualties. For lifelines (in particular watwould be prudent to quantify the consequential loss of service (l

users and traffic disruption). Indirect losses such as business and

included, and could be considered in a follow-on study as discussed

In general terms, loss (or numbers of breaks, etc) could be estimated

Loss = f (hazard, vulnerability, exposure), where:

o hazard is a condition that increases the chance of loss (e.g. pr

o vulnerability is the susceptibility to damage (e.g. earthquake

o exposure is the quantity exposed to earthquake (e.g. length o

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7.6.2 Infrastructure Inventory Modelling

General Approach

Obtaining reliable inventory data is the most difficult and ti

earthquake risk studies. It is therefore necessary to very carefu

model for each infrastructure type that will meet the requirements

while making use of data that are readily accessible. This requires

by engineers experienced in earthquake engineering.

Infrastructure inventory data would be collected from various sour

(a) Demography Statistics New Zealand

(b) Buildings (Residential, commercial and Industrial) from ECan

(c) Critical Facilities (Hospitals, Fire Stations, Police Station,

Centres)

(d) Roads CCC and Transit NZ

(e) Water Supply CCC

(f) Telecommunications Telecom, TelstraClear, Vodafone

(g) Electricity Orion, Transpower

The following assets should be covered in the study:

all residential, commercial and industrial buildings to e

casualties and numbers of homeless;

the water supply network to estimate the number and distribut

the main telecommunication, power and road networks to en

experienced from these networks and their impacts to be estim

A GIS theme would be formed for each type of infrastructure inven

include information supplied by the asset owners, CCC or E

classified according to their vulnerability to damage based on age

other infrastructure-specific characteristics.

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However, unlike in residential areas, in the central business d

generally very little uniformity between adjacent buildings. commercial buildings in the CBD, it maybe useful to obtain data f

considered to be significant.

The CBD buildings would be run through the earthquake ris

individual property level and then aggregated to mesh block

presentation of the results.

Additional information on the distribution of building classes wwould be obtained by drive-through surveys of representative s

supplement the information available from QV and other sources.

CCC has a register of earthquake risk buildings. The data is stored

used to prepare LIM reports. The council could supply a spreadsh

identifier. This information could be incorporated into a GIS mode

commercial buildings that are more likely to suffer extensive damag

The following buildings classes are proposed:

Occupancy:

Residential

Commercial

Industrial

Structural Class:

Timber frame

Light steel frame

Tilt-up concrete

Steel moment frame

Steel braced frame

Concrete moment frame

Concrete shear wall

Unreinforced masonry

Reinforced masonry

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Population

Population data will be obtained from Statistics New Zealand cen

census. This will provide night-time population data. Th

supplemented by information on employment in the CBD, o

population and transportation information from the Council

population data. This will enable estimation of casualties dep

earthquake happens at night or during the day.

Road Assets

Road asset information will need to be sourced from the Christc

Transit New Zealand, in GIS format as discussed in Section 5.3. In

obtained on the bridges and retaining structures on the priority ro

reports on the assessment of the earthquake performance of the brid

The road network would be prioritised using a range of factodeveloped by Brabhaharan et al (2001), and the risk assessment w

for the higher priority roads, rather than every road in the network

the consequences of failure of minor residential streets is small a

low. This will enable greater focus to be placed on the priority road

The roads will be characterised in terms of their vulnerability to fa

closure of the road. This would be dependent on the geology, heand liquefaction or slope failure potential. Retaining structures w

of the type, age and height. The characterisation of roads would be

reconnaissance by appropriate specialists, consistent with the a

Brabhaharan et al (2001).

Bridges on priority roads would be characterised by a bridge

through screening the bridges for earthquake vulnerability. Theviewing of bridge drawings where available and brief site reconna

the approach of HAZUS, but modified to reflect the bridge stock in

aspects of the state highway-screening programme developed

Consultants (1998) for Transit

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Telecommunications Assets

Telecommunication asset and location information would nee

Telecom, Telstra Clear and Vodafone. The exact extent of informa

discussed and agreed given the commercial sensitivity of th

telecommunication companies.

The asset information collated would include the type and age o

building data) and any recent seismic upgrades. Also the locatio

main fibre-optic land cable links should be obtained.

Electricity Assets

Information on the electricity assets would be obtained from Tran

would be GIS information on the location of assets as well as infor

and generic design of the assets (similar to buildings). Also the l

main electricity feeder lines should be obtained.

7.6.3 Hazard Modelling

Earthquake Scenarios

A scenario approach to the earthquake risk assessment is proposed

7.3 of this report.

Four earthquake scenarios are proposed, as summarised in Table 6.

The first three scenarios are discussed in Section 6.2.1.

The fourth scenario is a possible large earthquake on a hidden earth

10 km to 20 km) to Christchurch, perhaps an extension of the Nort

the Canterbury Plains. This is a conjectured source and would indi

from a large, say magnitude 7, earthquake in the Canterbury Plainsources are poorly understood, and could provide a possible e

scenario would require further consideration, and reviewed

knowledge before it is adopted as a scenario for the risk study.

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Foothills earthquake on

Ashley, Springbank, PortersPass-Amberley Faults

M 7.2

closer than 50 km 8

Hidden Canterbury Plains

Earthquake

M 7

At 10 km to 20 km9

Source Data

Fault data (locations, magnitudes, rupture type, recurrence intervathe Environment Canterbury (2004) Active Faults Database and

Institute of Geological & Nuclear Sciences, 1999). Further in

earthquake sources in the Canterbury plains would need to be ob

and Nuclear Science.

Attenuation

International trends in earthquake hazard and risk modelling (e.motions (e.g. PGA, spectral accelerations) as the earthquake inte

than MM intensity. McVerrys attenuation model (McVerry

developed from New Zealand earthquake data and is therefore th

this study.

Ground shaking in the Christchurch area would be derived from th

McVerry Attenuation relationships and mapped in GIS.

Microzonation

Microzonation effects should be taken into consideration by derivin

(a) Ground Class map, from the ground information collated by E

study of Christchurch (Beca, 2003).

(b) Liquefaction ground damage maps, derived by extrapolat

ground damage map prepared for the Alpine Fault event, for E

(c) Slope failure hazard maps, prepared using the broad scale

Christchurch lifelines study (Centre for Advanced Engine

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7.6.4 Damage Modelling

General Approach

A damage model could be developed for each asset type, which re

earthquake to the expected level of damage defined as damage sta

Buildings

The building damage modelling would be based on the HAZUS snone, slight, moderate, extensive and complete. Damage descripti

for each building class in each damage state.

The models would be in the form of fragility curves similar to th

They could be derived from HAZUS, ATC-13, New Zealand data (D

well relevant other data (e.g. from Northridge).

Estimates would also be made of damage due to post-earthquake fi

Peak Ground Acceleration (g)

Probability[Ds>

ds|PG

A

]

0.0000

0.2500

0.5000

0.7500

1.0000

0.00 0.20 0.40 0.60 0.80 1.00

Slight/Minor Moderate Extensive

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The damage state to water pipelines along roads (bridges, emba

structures) would be modified to reflect the damage state of structure.

Reservoir fragilities would be based on HAZUS and any other

developed. Pumping station fragilities would be suitably modified

0

1.4

0PGV (mm/sec)

RepairRateperkm

16% (ALA) Median (ALA)

84% (ALA) Data Points (ALA)

Figure 12 - Typical Fragility Curve for Pipelines from AL

Outputs would be: numbers of pipe repairs, reservoir damage state

states.

Telecommunications

Telephone exchange fragility models could be suitably modified

Models could also be developed for cable fragilities (buried and pol

Power Supply

Substation fragility models could be suitably modified from bu

could also be developed for cable fragilities (buried and pole moun

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The fragility models for the roads could be based on the road char

7.6.2) and the approach developed by Brabhaharan et al (2001), developed for a current Transfund Research project (Brabhaharan

would provide damage states for the road.

7.6.5 Loss Modelling

Economic Loss

Economic loss estimates would be limited to cost of repairing blosses are calculated by assigning damage ratios (cost of repair/r

damage states.

While it is possible to estimate the cost of repairing other infrastru

power cables, etc, this would require the total inventory to be mod

main networks, which is not the intention of this study.

Loss of Function

The impact of the damage on the functioning of the lifelines could

be modelled as availability /outage states.

The consequence of damage to the pipelines, electricity and teleco

assessed as the loss of supply to properties, and the consequence of

traffic disruption.

Casualties

Deaths and injuries are principally attributable to the failure of m

facilities. Of these the largest proportion of casualties would be due

The casualties could be estimated for a day-time and night-time

population estimated as discussed in 7.6.2.

The model proposed is to generally follow the HAZUS approach.

7.7 Risk Assessment Outputs

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(d) Numbers of casualties.

(e) Damage state in terms of repairs per kilometre for main wat

example in Appendix B).

(f) Damage state of reservoirs and pump stations.

(g) Damage state of the core telecommunication network.

(h) Damage state of telephone exchanges.

(i) Damage state of core power supply network.

(j) Damage state of electricity subs

christchurch earthquake risk assessment stage1 report

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