Earthquakes And Housing

Prof. David AlexanderProf. David AlexanderCESPROCESPRO - University of Florence- University of FlorenceProf. David AlexanderProf. David Alexander

CESPROCESPRO - University of Florence- University of Florence

Earthquakes and HousingEarthquakes and HousingHow to Develop a Survival StrategyHow to Develop a Survival Strategy

Earthquakes and HousingEarthquakes and HousingHow to Develop a Survival StrategyHow to Develop a Survival Strategy

Past Past eveneven

tsts

Past Past eveneven

tsts

AnalysisAnalysisAnalysisAnalysis

• registereregisteredd• archivedarchived• forgottenforgotten• ignoredignored

• registereregisteredd• archivedarchived• forgottenforgotten• ignoredignored

VulnerabilityVulnerabilitymaintainedmaintained..VulnerabilityVulnerabilitymaintainedmaintained..----

• utilisedutilised• adoptedadopted• learnedlearned

• utilisedutilised• adoptedadopted• learnedlearned

DisasterDisasterriskriskreducedreduced

DisasterDisasterriskriskreducedreduced

++++

LessonsLessonsLessonsLessons

• 3030 disasters (including seismic disasters (including seismic seawaves)seawaves)

• 3030 disasters (including seismic disasters (including seismic seawaves)seawaves)

• 47,35047,350 deaths (varies from year to deaths (varies from year to year by two orders of magnitude)year by two orders of magnitude)

• 47,35047,350 deaths (varies from year to deaths (varies from year to year by two orders of magnitude)year by two orders of magnitude)

• 8.58.5 million people affected million people affected• 8.58.5 million people affected million people affected

• $23$23 billion in damage billion in damage (second only to hurricanes)(second only to hurricanes)

• $23$23 billion in damage billion in damage (second only to hurricanes)(second only to hurricanes)

• 60%60% of disasters occurred in Asia of disasters occurred in Asia..• 60%60% of disasters occurred in Asia of disasters occurred in Asia..

Mean annual impact of earthquakes(1999-2008 data)

At the world scale, most injuriesAt the world scale, most injuriesoccur in nocturnal earthquakes:occur in nocturnal earthquakes:• a sleeping person is nota sleeping person is not able to react rapidlyable to react rapidly• vernacular housing is particularly at riskvernacular housing is particularly at risk• 50-90% of mortality is nocturnal50-90% of mortality is nocturnal..

VernacularVernacularhousing:housing:the mainthe mainsourcesourceof riskof risk

VernacularVernacularhousing:housing:the mainthe mainsourcesourceof riskof risk

A scale for damage and personal risk levelA scale for damage and personal risk level

Damage level: Damage level: [1] [1] minimum damageminimum damageto walls, fitments and furniture.to walls, fitments and furniture.

Personal risk level: Personal risk level: prudentprudentbehaviour will minimise risksbehaviour will minimise risks..

Damage level: Damage level: [1] [1] minimum damageminimum damageto walls, fitments and furniture.to walls, fitments and furniture.

Personal risk level: Personal risk level: prudentprudentbehaviour will minimise risksbehaviour will minimise risks..

Damage level: Damage level: [2][2] significant damageto structures, cladding and fitments.

Personal risk level: Personal risk level: significantrisk of injury but not of death..

Damage level: Damage level: [2][2] significant damageto structures, cladding and fitments.

Personal risk level: Personal risk level: significantrisk of injury but not of death..


Damage level: Damage level: [3][3] general damage andcollapse of architectural elements.

Personal risk level: Personal risk level: significant risk ofinjury but relatively low risk of death.

Damage level: Damage level: [3][3] general damage andcollapse of architectural elements.

Personal risk level: Personal risk level: significant risk ofinjury but relatively low risk of death.


Damage level: Damage level: [4][4] serious damageor partial collapse of building.

Personal risk level: Personal risk level: strong risk ofinjury and significant risk of death.

Damage level: Damage level: [4][4] serious damageor partial collapse of building.

Personal risk level: Personal risk level: strong risk ofinjury and significant risk of death.


Damage level: Damage level: [5][5] collapse ofmore than 50% of the structure.

Personal risk level: Personal risk level: limited and mainlyunpredictable probability of survival.

Damage level: Damage level: [5][5] collapse ofmore than 50% of the structure.

Personal risk level: Personal risk level: limited and mainlyunpredictable probability of survival.


Survival strategiescould be improvedfor levels 1-4but perhaps notfor level 5(total collapse)

Survival strategiescould be improvedfor levels 1-4but perhaps notfor level 5(total collapse)

Poor buildingPoor buildingqualityquality

(low seismic(low seismicresistance)resistance)

Poor buildingPoor buildingqualityquality

(low seismic(low seismicresistance)resistance)

ProximityProximityto epicentreto epicentre

and faultand faultrupturerupture

ProximityProximityto epicentreto epicentre

and faultand faultrupturerupture

TopographicTopographicamplificationamplificationTopographicTopographicamplificationamplification

SedimentarySedimentaryamplificationamplificationSedimentarySedimentaryamplificationamplification

QQQQ EEEE

TTTT SSSS

ConcentrationConcentrationof casualtiesof casualties

CC

ConcentrationConcentrationof casualtiesof casualties

CC

C = C = f f { E,Q,S,T }{ E,Q,S,T }C = C = f f { E,Q,S,T }{ E,Q,S,T }

Building quality and seismic resistance:Building quality and seismic resistance:Building quality and seismic resistance:Building quality and seismic resistance:

• site factorssite factors• site factorssite factors


• building type and materialsbuilding type and materials• building type and materialsbuilding type and materials

[Masonry] [Reinforced concrete][Masonry] [Reinforced concrete][Masonry] [Reinforced concrete][Masonry] [Reinforced concrete]

• plan and elevation of buildingplan and elevation of building• plan and elevation of buildingplan and elevation of building



• urban form factorsurban form factors• urban form factorsurban form factors

[battering[battering byby adjacentadjacent buildings]buildings]

[battering[battering byby adjacentadjacent buildings]buildings]


• mixed construction?mixed construction?• mixed construction?mixed construction?

[Stone and[Stone and concreteconcrete block]block]

[Stone and[Stone and concreteconcrete block]block]


• state of maintenancestate of maintenance• state of maintenancestate of maintenance


• occupancy factorsoccupancy factors• occupancy factorsoccupancy factors

An example:An example: the L'Aquila (Italy) the L'Aquila (Italy)earthquake of 6 April 2009earthquake of 6 April 2009

An example:An example: the L'Aquila (Italy) the L'Aquila (Italy)earthquake of 6 April 2009earthquake of 6 April 2009

L'Aquila:- L'Aquila:- • a university citya university city• population 72,800population 72,800• 14 outlying villages14 outlying villages

L'Aquila:- L'Aquila:- • a university citya university city• population 72,800population 72,800• 14 outlying villages14 outlying villages

96 municipalities reported damage96 municipalities reported damage96 municipalities reported damage96 municipalities reported damage

The earthquakeThe earthquakeThe earthquakeThe earthquake

03.32 hrs, Monday 6 April 200903.32 hrs, Monday 6 April 2009Magnitude MMagnitude Mww 6,3 6,3

Duration 25 secondsDuration 25 secondsAcceleration on hard rock 0,3gAcceleration on hard rock 0,3gAcceleration on sediments 0,7-Acceleration on sediments 0,7-

1,0g1,0gPart of an earthquake swarm Part of an earthquake swarm

fromfromOctober 2008 to July 2009October 2008 to July 2009..

03.32 hrs, Monday 6 April 200903.32 hrs, Monday 6 April 2009Magnitude MMagnitude Mww 6,3 6,3

Duration 25 secondsDuration 25 secondsAcceleration on hard rock 0,3gAcceleration on hard rock 0,3gAcceleration on sediments 0,7-Acceleration on sediments 0,7-

1,0g1,0gPart of an earthquake swarm Part of an earthquake swarm

fromfromOctober 2008 to July 2009October 2008 to July 2009..

Significance of the L'Aquila disaster:Significance of the L'Aquila disaster:Significance of the L'Aquila disaster:Significance of the L'Aquila disaster:

• It was a relatively It was a relatively small eventsmall event with with a disproportionately a disproportionately large impactlarge impact

• It was a relatively It was a relatively small eventsmall event with with a disproportionately a disproportionately large impactlarge impact

• Medium-size earthquake disastersMedium-size earthquake disasters are more common than large onesare more common than large ones and deserve to be and deserve to be studied morestudied more..

• Medium-size earthquake disastersMedium-size earthquake disasters are more common than large onesare more common than large ones and deserve to be and deserve to be studied morestudied more..

24 km24 km

11 k

m11 k

m

Distribution of deaths in theL'Aquila earthquake of 6/4/09Distribution of deaths in theL'Aquila earthquake of 6/4/09

L'AquilaL'AquilaL'AquilaL'Aquila

OnnaOnnaOnnaOnna

6-25 deaths 3-5 deaths 1-2 deaths

No deathsNo deathsNo deathsNo deaths

One or two individualsOne or two individualsOne or two individualsOne or two individuals

ClustersClustersof multipleof multiple

deathsdeaths

ClustersClustersof multipleof multiple

deathsdeaths

n=202

L'Aquila city

No deaths:No deaths:housing stock washousing stock wasin relatively goodin relatively good

condition andcondition anddamage was limiteddamage was limited

No deaths:No deaths:housing stock washousing stock wasin relatively goodin relatively good

condition andcondition anddamage was limiteddamage was limited

Damage/riskDamage/riskscale: 1-2scale: 1-2


One or two individuals:One or two individuals:people rushed outsidepeople rushed outside

and were killed byand were killed byfalling masonryfalling masonry

One or two individuals:One or two individuals:people rushed outsidepeople rushed outside

and were killed byand were killed byfalling masonryfalling masonry



Clusters of Clusters of multiple deaths:multiple deaths:

spectacular collapsesspectacular collapsesof multi-occupancyof multi-occupancybuildings with upbuildings with up

to 25 deaths each:to 25 deaths each:topographictopographic

amplification was anamplification was anadditional factoradditional factor..

Clusters of Clusters of multiple deaths:multiple deaths:

spectacular collapsesspectacular collapsesof multi-occupancyof multi-occupancybuildings with upbuildings with up

to 25 deaths each:to 25 deaths each:topographictopographic

amplification was anamplification was anadditional factoradditional factor..

Damage/riskDamage/riskscale: 5scale: 5

Damage/riskDamage/riskscale: 5scale: 5

Mid-floor damage to multi-occupancy bldg:Mid-floor damage to multi-occupancy bldg:

Intertia effectIntertia effectIntertia effectIntertia effect

Basal accelerationBasal accelerationBasal accelerationBasal acceleration

Interaction = damageInteraction = damageInteraction = damageInteraction = damage

Lack of stiffness in frameLack of stiffness in frameLack of stiffness in frameLack of stiffness in frame

Incipient collapse of intermediate floorsIncipient collapse of intermediate floorscaused by lack of stiffness in structure.caused by lack of stiffness in structure.

Incipient collapse of intermediate floorsIncipient collapse of intermediate floorscaused by lack of stiffness in structure.caused by lack of stiffness in structure.

Column breakageColumn breakageColumn breakageColumn breakage

Typical forms of damage in RCTypical forms of damage in RCTypical forms of damage in RCTypical forms of damage in RC

Collapse of intermediate floor causedCollapse of intermediate floor causedby battering by adjacent retaining wall.by battering by adjacent retaining wall.Collapse of intermediate floor causedCollapse of intermediate floor caused

by battering by adjacent retaining wall.by battering by adjacent retaining wall.


Two deathsTwo deathsTwo deathsTwo deaths

Collapse of 'soft storey' groundCollapse of 'soft storey' groundfloor which had insufficient stiffness.floor which had insufficient stiffness.Collapse of 'soft storey' groundCollapse of 'soft storey' groundfloor which had insufficient stiffness.floor which had insufficient stiffness.


TotalTotalcompressioncompressionof floorof floor

TotalTotalcompressioncompressionof floorof floor


Detachment, fragmentationDetachment, fragmentationand expulsion of infill walls.and expulsion of infill walls.Detachment, fragmentationDetachment, fragmentationand expulsion of infill walls.and expulsion of infill walls.

Rackingfailure

Typical forms of damage in URMBTypical forms of damage in URMBTypical forms of damage in URMBTypical forms of damage in URMB

Load-bearing walls disintegrate at Load-bearing walls disintegrate at angles.angles.

Load-bearing walls disintegrate at Load-bearing walls disintegrate at angles.angles.

Typical forms of damage in masonryTypical forms of damage in masonryTypical forms of damage in masonryTypical forms of damage in masonry

Excessively heavy roof in RC: subsides.Excessively heavy roof in RC: subsides.Excessively heavy roof in RC: subsides.Excessively heavy roof in RC: subsides.

Typical forms of damage in masonryTypical forms of damage in masonryTypical forms of damage in masonryTypical forms of damage in masonry

Detachment of facade elementsDetachment of facade elementsand fall of roof tiles.and fall of roof tiles.

Detachment of facade elementsDetachment of facade elementsand fall of roof tiles.and fall of roof tiles.

People are killed or injuredPeople are killed or injuredbecause they because they lack:lack:• experience experience of earthquakesof earthquakes• perceptionperception of seismic risk of seismic risk• adaptabilityadaptability to the risks to the risks• social discussionsocial discussion of the of the seismic risk problemseismic risk problem• wealth accumulation andwealth accumulation and investmentinvestment in protection in protection• training and training and practicepractice in dealing in dealing with earthquake hazardswith earthquake hazards• social social supportsupport networks networks..

Unexpected earthquakeUnexpected earthquakeUnexpected earthquakeUnexpected earthquake

MildMildimpactimpactMildMildimpactimpact

SevereSevereimpactimpactSevereSevereimpactimpact

CatastrophicCatastrophicimpactimpact

CatastrophicCatastrophicimpactimpact

VeryVerylimitedlimiteddamagedamage

VeryVerylimitedlimiteddamagedamage

Fall ofFall ofheavyheavy

objectsobjects

Fall ofFall ofheavyheavy

objectsobjects

PartialPartialcollapsecollapsePartialPartial

collapsecollapseTotalTotal

collapsecollapseTotalTotal

collapsecollapse

Absolute immobilityAbsolute immobilityAbsolute immobilityAbsolute immobility Frantic egressFrantic egressFrantic egressFrantic egress

UninjuredUninjuredUninjuredUninjured LightlyLightlyinjuredinjuredLightlyLightlyinjuredinjured

SeriouslySeriouslyinjuredinjured

SeriouslySeriouslyinjuredinjured KilledKilledKilledKilled

Models of Models of typical typical

vernacular vernacular housinghousing

building typesbuilding typesAnalysis ofAnalysis ofcharacteristcharacterist

icicfailure failure modesmodes

DeterminatioDeterminationnof of

appropriateappropriatecrisis crisis

behaviourbehaviour Education Education andand

training oftraining ofhouseholdshouseholds

Culture ofCulture ofprotectionprotection

and and resilienceresilience

Kang, NW Irana mountain villagein a seismic area

Kang, NW Irana mountain villagein a seismic area

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Earthquakes And Housing

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