the padang, sumatra - indonesia earthquake of 30

THE PADANG, SUMATRA - INDONESIA EARTHQUAKE OF 30 SEPTEMBER 2009

A FIELD REPORT BY EEFIT

ThePadang,Sumatra‐IndonesiaEarthquakeof30September2009

THE PADANG, SUMATRA - INDONESIA EARTHQUAKE OF 30

SEPTEMBER 2009

AFIELDREPORTBYEEFIT

SeanWilkinson(Editor)

JohnAlarcon

RiniMulyani

JessicaWhittle

DarrenSiauChenChian

EarthquakeEngineeringFieldInvestigationTeamInstitutionofStructuralEngineers

11UpperBelgraveStreetLondonSW1X8BHTel02072354535Fax02072354294

Email:[email protected]

ThePadang,Sumatra‐IndonesiaEarthquakeof30September2009

CONTENTS

1. ACKNOWLEDGEMENTS ........................................................................... 1

2. INTRODUCTION ...................................................................................... 2

THEMISSION ....................................................................................................... 2

3. REGIONALSEISMICITY............................................................................. 7

THE30THSEPTEMBEREVENT.................................................................................. 10

4. FIELDSURVEYRESULTS ......................................................................... 15

STRUCTURALPERFORMANCE ................................................................................. 15Structuraltypology, .................................................................................... 15ThePrincipalissues..................................................................................... 16Impactonoccupants .................................................................................. 17Residential .................................................................................................. 21Commercial................................................................................................. 26GovernmentBuildings ................................................................................ 35IndustrialBuildings ..................................................................................... 39Portfacilities............................................................................................... 42Schools........................................................................................................ 43Hospitals ..................................................................................................... 48

LIFELINES........................................................................................................ 53WaterSupply .............................................................................................. 53TransportNetworks.................................................................................... 55Telecommunication .................................................................................... 57

GEOTECHNICALASPECTS ............................................................................... 58FoundationFailures .................................................................................... 58Landslides ................................................................................................... 60Liquefaction ................................................................................................ 69

DISASTERMANAGEMENT .............................................................................. 72

5. CONCLUSIONSANDRECOMMENDATIONS ............................................ 79

6. REFERENCES.......................................................................................... 81

ThePadang,Sumatra‐IndonesiaEarthquakeof30September2009 Page1

1. ACKNOWLEDGEMENTS

The authorswould like to express their thanks to themany individuals andorganisationsthathaveassistedwiththeEEFITmissiontoSumatraandinthepreparationofthisreport.

WefirstlythankAIRWorldwideforenablingJohnAlarcontoattendthismission

WewouldparticularlyliketothanktheEngineeringandPhysicalSciencesResearchCouncilforprovidingfundingforSeanWilkinson,RiniMulyani,JessicaWhittleandDarrenChiantojointheteam.TheircontinuedsupportinenablingUKacademicstowitnesstheaftermathofearthquakesandtheeffectsonstructuresandthecommunities theyserve isgratefullyacknowledged.

We also thank other members of EEFIT who provided support in getting the mission toPadang and for providing supportwhile the teammemberswere there. In particularwewouldliketoacknowledgethesupportofBereniceChan,NavinPeiris,TizianaRossettoandMatthewFree.

FinallyweexpressourgratitudetoourcorporatesponsorswithoutwhosehelpEEFITcouldnot continue as a viable organisation: they are Arup, AIRWorldwide, Aon Benfield, BGS,CREAConsultants,RMSandSellafieldLtd.


2. INTRODUCTION

On the 30th September 2009, a Moment MagnitudeMw7.6 earthquake occurred off theisland of Sumatra, Indonesia, near the city of Padang. This earthquake had a devastatingeffect on many of the buildings and affected infrastructure and communities there. Theepicentre of the event occurred in the same region as the 2004 Sumatra‐AndamanearthquakethatgeneratedaTsunamiresulting in thedeathsofover200,000people.Theearthquakeepicentrewasabout54kilometreswestnorthwestofthelow‐lyingcoastalcityofPadang(populationaround900,000),thecapitalof Indonesia’sWestSumatraprovince,and the home to many large hotels, some of which were either severely damaged orcollapsed.Twohospitalsandalargeshoppingcentreweresignificantlyaffectedaswell.

Following the earthquake, theUK‐based Earthquake Engineering Field Investigation Team(EEFIT) mounted a reconnaissance mission to the Padang region in Sumatra. This reportpresentssomeofthepreliminaryfindingsoftheteam.AnumberofpicturestakenbytheEEFIT Team have been uploaded for free views on the Virtual Disaster Viewer(www.virtualdisasterviewer.com).

THEMISSIONOn16thOctobertheEEFITmanagementcommitteedecidedtolaunchamissiontoPadangand the area affected by the 30th September earthquake. With this purpose Dr SeanWilkinson was selected as team leader for the mission. The other team members wereselectedtocoverawiderangeofexpertises includingengineeringseismology,earthquakeengineering, structural engineering, seismic risk analysis, risk modelling, lifelines andgeotechnical earthquakeengineering. The teammembersare introduced in Figure1andTable1.


Figure1.SumatraEEFITmissionmembers.Fromleft:JohnE.Alarcon,SeanWilkinson,RiniMulyani,JessicaWhittleandSiauChen(Darren)Chian.

Table1.TheEEFITPadangteam.

Name MissionRole,Position Institution Expertise

SeanWilkinsonTeamLeader,SeniorLecturer

NewcastleUniversityStructuralengineering,Non‐lineardynamics

JohnAlarconDeputyTeamLeader,ResearchAssociate

AIRWorldwideSeismichazardassessment,Riskmodelling

RiniMulyani PhDStudentTheUniversityofSheffield

Seismicriskanalysis

SiauChenChian PhDStudent UniversityofCambridge

Geotechnicalearthquakeengineering

JessicaWhittle PhDStudent UniversityofOxfordStructuralearthquakeengineering

TheteamflewintoPadangAirportintheeveningofthe7thofNovemberandthenspent5dayssurveyingPadangCityandthesurroundingarea.AmapofthesurveysitescanbeseeninFigure2,Figure3andFigure4.Themissionfinishedonthe13thNovember;however,RiniMulyanistayedinIndonesiatocollectmoredata.


Figure2.MapofkeysurveysitesinPadang(labelsindicatedayandsequenceofvisit).

Figure3.MapofvisitedsitesinthecentralregionofPadangcity.

Details in Figure 3


Figure4.MapofkeysurveysitesinPariaman.

Themissionhadtwomainaims.ThefirstwastocarryoutafieldInvestigationtocollectdataonbuildingandinfrastructureperformanceandgeotechnicalfailures,whilethesecondaimwastocollectlandslidedatatohelpassessingthefeasibilityofusingsatellitedatatocollectlandslideinformation.ThespecificaimsandobjectiveswereI)FieldInvestigationandDataCollectionObjectives:

1. To carry out a detailed technical evaluation of the performance of structures,foundations, civil engineering works, industrial plants and natural geographicalfeatureswithintheaffectedregion.

2. Toassesstheeffectivenessofearthquakeprotectionmethods, includingrepairandretrofit,andtomakecomparisonsoftheactualperformanceofstructureswiththeexpectationsofdesigners.

3. To study disaster management and recovery procedures associated with thisearthquake,toseehoweffectivethesewerepost‐2004,andtodevelopindicatorsofresilience.

4. To train new researchers in the techniques of earthquake investigation and dataanalysis.

5. Toobserveandreviewlocalconstructionmaterialsandmethods.6. Toreportonthemissionfindings.


II)DevelopmentofDataAnalysisToolsandDataAnalysisObjectives:1. Toobserveandcollectdataonlandslidesanddeterminetheirdamagingeffectson

infrastructure.2. Toassessthefeasibilityofdevelopingasystemthatcanpredictthesusceptibilityof

natural slopes to earthquake induced landslidesusing satellite imagery andexpertinterpretation.

ThemissioncoveredmostofPadang,surveyingbuildingsinChinaTown(Pondok),Jati,UlakKarang,CityCentreandAirTawar.TheoutlyingdistrictofPariamanwasalsovisited.

Aspartofthemissionanumberofinterviewswereconductedwiththestafffromthemainhospital in Padang, engineers from the water supply company, engineers from the localuniversity,NGOrepresentativesandlocalresidents.


3. REGIONALSEISMICITY

The territory coveredby Indonesia lieswithin thePacificRingof Fire,where someof thelargestrecordedearthquakesintheworldhavetakenplace.Theseismicityintheregioniscontrolled by the subduction of the Australian plate beneath the Eurasian plate. ThesubductionbetweenthesetectonicplatesoccursalongthewesternsideofSumatraformingtheSundatrench(Figure5).Thedipangleofthesubducting intheuppermostpartofthecontactbetweentheplatesisofabout13°‐15°(Irsyametal.,2008).

Figure5.LocationofIndonesiawithinthePacificringoffire(blackrectangle).ThesubductionontheWesternsideofthecountrycorrespondstotheSundatrench.

The velocity of the relative motion between the Australian and Eurasian plates variesaccordingtotheareastudied;itiscalculatedatabout52mmperyearatthenorthernpartof Sumatra and at 62 mm per year at the southern part, as illustrated in Figure 6(Natawidjaja,2002).Atdepth,thesubductionalongSumatraextendsintotheBenioffzonetodepthsofupto200km.IntheBenioffzone,theAustralianplatesubductsatadipangleof about 40°‐45°. Considering the hypocentral location of the 30 September 2009earthquake,beingoff‐shorePadangPariaman(seedetailsbelow),theeventisestimatedtohaveoccurredintheBenioffzone.


Figure6.TectonicsettingofSumatra(Natawidjaja,2002).

Thesubductionzone inSumatra isknown forproducingmega‐thrustearthquakessuchasthe moment magnitude Mw 8.8‐9.2 in 1833, the Mw 8.3‐8.5 in 1861, the Mw 9.0‐9.3 inDecember2004,theMw8.7inMarch2005andtheMw8.4inSeptember2007(Irsyametal.,2008).Basedontherecentseismicactivity,Aydanetal.(2007)identifiedasegmentofthesubductionzonefacingPadangCitythathasnotrupturedinthelast213years.Thisseismicgap has the potential to produce an earthquake with magnitude greater than 8.7. Theseismicgapis locatedinbetweenthe1833and1861faultruptures,andit isestimatedtohaveanapproximaterecurrenceintervalof230years(Zachariasen,1999).

AnotherimportantseismicfeatureintheregionistheSumatrafault(seeFigure6andFigure7),thataccommodatestheobliqueconvergencesoftheAustralianandtheEurasianplates.Natawidjaja(2002)mappedtheSumatranFaultandfoundthatitisatrench‐parallelstrike‐slipfaultsystem,1900kmlongextendingfromNorthtoSouthofSumatra.Thefaultishighlysegmented,withthemajorityofthesesegmentsbeingoflessthan100km.Asaresult,thepotentialearthquakerupturelengthintheSumatrafaultisnotlikelytoexceed100km,sothemaximummagnitudeexpectedfromsuchaneventisestimatedasMw7.5(Natawidjaja,2002;McCaffrey,2009).


Figure7.LargeeventsintheSundatrenchalongSumatraandtheirassociatedruptureareas(Chliehetal.,2008).Notearecentseismicgapbetweenthe1833and1861events,ontheregionwherethe1797eventoccurred.Thestarshowstheepicentrallocationoftheevent.

The convergence between the Australian and Eurasian plates described above has alsocausedaslippartitioningprocessthathasformedasliverplate,calledasSundaforearc,asillustrated inFigure8.Thesliverplate isenclosedbytheSumatrasubductionzoneonthewestandtheSumatrafaultontheeast(McCaffrey,2009).


Figure8.(a).CrosssectionofSumatraPlateBoundary;(b).Geometryofsliverplate(McCaffrey,2009).

THE30THSEPTEMBEREVENTTheearthquakeoccurredat17hr16min09seclocaltime(10hr16minGMT)offthecoastofSumatra,intheBenioffzoneoftheSundatrenchpreviouslydescribed(seelocationinFigure7).A summaryof the location, depthandmagnitudes assigned to this earthquakeby thelocalandfourinternationalagenciesisshowninTable2.AfacttomentionfromthelattertableisthattheepicentrallocationassignedbythelocalIndonesianagency(BMKG)differsfrom the international agencies by about 22 km. The focal depth also shows a variationbetween the local seismological service and the other agencies,with the first assigning afocaldepthof71kmwhileotherestimatesplace the focaldepthataround80km.Smalldifferencesinthemagnitudeoftheeventarealsoappreciated,thoughthesedifferencesarenotsignificant.

(a).

(b).


Figure 9 presents the fault plane proposed by the French CEA (Commissariat a l’EnergieAtomique),andtheareaswheretheslipisconcentrated.Inthesamefigurethelocationandsizeofashallowearthquake(10km)withmagnitudeMw6.8isalsoshown.Thisaftershockoccurredon1stOctoberandhaditsepicentreabout180kmfromPadang.

Table2.Earthquakeparameters.

LocationAgency

Latitude(S) Longitude(E)

Focaldepth(km)

MagnitudeMw

BMKG(Local) 0.84 99.65 71 7.6EMSC 0.76 99.84 80 7.6GFZ(Germany) 0.78 99.87 80 7.7CEA(France) 0.79 99.82 80 7.6USGS(USA) 0.72 99.87 81 7.5Notes: BMKG – Badan Meteorologi Klimatologi dan Geofisika; EMSC – European‐MediterraneanSeismologicalCentre;GFZ–GermanResearchCentreforGeosciences;CEA–Commissariatal’EnergyAtomique;USGS–UnitedStatesGeologicalSurvey

Figure9.FaultplaneproposedbytheCEAforthe30thSeptemberMw7.6Padangearthquake.ThestarshowsthelocationofPadang.Notethecalculatedfaultplaneofthe1st

OctoberMw6.8earthquaketotheSoutheastofthelargestevent.


Duringtheearthquake,BMKGandUSGSrecordedamaximumpeakgroundaccelerationof0.3g,which lastedabout20seconds(Figure10). Consideringthattheaccelerationrecordwas taken from a locationwith relatively stiff soil, the earthquake ground shakingwouldhavebeenamplifiedatPadangcity.PadangCityliesonrelativelythickalluviumdepositsasshown in Figure 11 (ESDM 2009). As a result, it was estimated that the earthquakeproducedPGAsaround0.4g‐0.6gacrossPadangCity(EERI,2009).

Figure10.Groundaccelerationandresponsespectra(N‐Scomponent)anddesignearthquakespectra(EERI,2009).


Figure11.GeologicalMapofPadangCity(GeologicalAgency‐DepartmentofEnergyandMineralResourcesofRepublicofIndonesia,ESDM2009)

Figure12presents the results of two seismichazard analyses for Indonesia and Sumatra.ThefirstcorrespondstothehazardmapincludedintheIndonesiandesigncode,forwhichgroundmotionson rockwitha returnperiodof475years isof0.25g forPadang.On theotherhand,thehazardassessmentofPetersenetal.(2004)presentsaccelerationvaluesofup to 0.4g for the same return period, which represents a significant difference in thehazardresults.

AccelerographLocation


Figure12.SeismichazardmapsforIndonesiaandSumatra.Top:theIndonesiandesigncode(SNI‐1726‐2002).Bottom:Petersenetal.(2004).


4. FIELDSURVEYRESULTS

STRUCTURALPERFORMANCE

Structuraltypology,Thestructures inPadangareprimarilymadeofeitherunreinforcedmasonryorreinforcedconcreteframeswithmasonryinfill.Theconfinementtothemasonryisusuallyprovidedbythe structural framing of reinforced concrete buildings The planning regulations limitedbuildingheights to six storeysprior to the relocationof theairport in 2005;however thevast majority of structures are one or two storey residential or two storey commercial.There are virtually no steel buildings in the city; however one was observed. The buildquality was typical for a region at this stage of development with the majority of smallstructuresbeingverypoorlyconstructedwithpoorqualitybuildingmaterialsandlittleornoplanning permission. Of the larger engineered structures the quality of constructionwasoften reasonable, but poor build qualitywas also observed. Typical structural typologiescanbeseenInTable3.

Table3StructuralTypologies

StructuralTypologyTypical

Occupancy

NumberofStories

Example

TimberorBamboo Residential 1‐2

Stoneor

Stone&BrickResidential 1‐2


Unreinforced

Masonry

Residential/Schools/Commercial

1‐2

ReinforcedConcretewithBrickMasonry

Infill(typicallyunreinforced)

Residential/Schools/Commercial

1‐2

ReinforcedConcretewithBrickMasonry

Infill(typicallyunreinforced)

Commercial/Industrial/Hospitals

/Government2+

SteelCommercial/Industrial

2+

ThePrincipalissuesThe first issue is associated with the lack of a single design code for the entire countrybefore1983andthe latestcodedatingfrom2002. From2002,engineeredstructuresareobligedtomeettherequirementsofthenationalseismiccodeSNI‐1726‐2002,whichcanbedescribedasamoderncodesimilartoeitherAmericanorEuropeanequivalents;however,beforethisdate,engineeredstructureswereoftendesignedfollowinglocalbuildingdesignpractices. This isdue to Indonesiabeingadministrativelydividedasaunitary statewhereeachprovincehasitsownlegislature.Fromthe320municipalitiesinIndonesia,onlyabout210 (70%of the total) had local building regulations. From these 210municipalities, onlyabout 45 regulated the technical parameters of designwhile the rest only regulated thebuildingpermitprocessanditspermitfees(Budiono,2004).Thismayexplaintheseemingly


inadequatesupervisionofeitherthedesignsortheconstructionprocess. DuringthefieldEEFIT survey, very large spacingbetweenconfining links,particularlyat thebeam/columnunions,wascommonlyobservedincollapsedreinforcedconcretebuildings.Theuseofplainbarsforlinksandmainreinforcementinsteadofribbedbarswasanothercommonfeatureobservedincollapsedbuildings.Softstoreycollapsewasprobablythemajorcontributortothecollapseofmajorengineeredstructures.

ImpactonoccupantsThe impact of the earthquake on occupants can be roughly assessed by the number ofcasualties,thedamagetostructures,theimpactonthelivelihoodsandeffectoneducation,the loss of data and equipment, the current state of critical facilities, and finally, thepsychologicalresponseoftheresidents.

Asaresultof theWesternSumatraearthquaketherewereapproximately1,117fatalities,2,902injuries(1,214peoplewithmajorinjuriesand1,688slightlyinjured),and186peoplemissing,accordingtoNationalDisasterManagementAgency(BNPB,2009).

Figure13indicatesthedistributionoffatalitiesintheregion.SixtypercentofthefatalitiesoccurredinPadangPariamanCounty,whereatleast321deathsduetothelandslideswerereportedby thePariamangovernment. Three villageswere completely destroyedby thelandslides (please refer to the geotechnical section of this report for additional details).Twenty‐eight percent of the fatalities (313 deaths) occurred in Padang City and sevenpercent of the fatalities (80 deaths) occurred in Agam County (BNPB, 2009). Figure 76indicatesthelocationofthesecounties.

Figure13.DistributionofFatalities(total1117fatalities)(BNPB,2009).


There was also extensive damage to residential buildings, resulting in 135,000 severelydamaged buildings, 65,000 moderately damaged buildings, and 78,000 lightly damagedbuildings (BNPB,2009).Refer to theDisasterManagement section formoredetailsaboutthe post‐earthquake assessment of damaged buildings and identification of temporaryshelterneeds.BecauseoftheclosefamilynetworkinSumatra,itwouldbeverycommonfora family thathad lost theirhome in theearthquake tomove inwithother relatives. Thisfamily support systemand the lapse in timeafter theearthquakemayexplainwhy therewerefewtemporaryresidentialsheltersandnomajorrefugeeproblemsintheareawhentheteamvisited.InthevillageofCumanakinthePadangPariamancounty,therewerestillresidentsclearingthedebrisandcollectingtimberfromthelandsliderubbleforrebuildingof their homes (Figure 14). In the town of Siteba Perumdam, severe residential buildingdamage had been caused by the earthquake and resulting liquefaction. This had notnecessarily displacedmanyof the residents, but instead, rendered the damaged roomorpartofthehouseunusable(Figure15).

Figure14.ResidentsRemovingTimberfortheCumanakvillagelandslidearea.


Figure15.SitebaPerumdamVillageHomewithFoundationFailures,StillOccupied.

Withtheclosureofmanyhotelsandextensivedamagetonumerouscommercialbuildingsand shopping centres, the loss of livelihood was another detrimental impact of theearthquakeonSumatranresidents.However,withtheincreasedneedforlabourerstohelpwith demolition work and reconstruction, labour and construction jobs have increased(Figure16).Asisoftenthecasewithadisastersuchasthis,theneedforrebuildinginflatesmaterialand labourcosts intheregions. Academicsandengineers fromtheUniversityofBung Hatta confirmed that thiswas indeed the case for this eventwith inflation in bothmaterialsandlabour.Themostdramaticinflationhasbeeninthecostoflabourwhichwasquotedtohaveinflated300%.

Despite the high degree of government building damage, it is expected that thegovernment employees’ jobs will be only marginally affected. There has been aninconvenience to the employees of many businesses as they have had to move totemporaryfacilities.Insomecases,suchasmanysmallretailshopsinsomeareasofChinatown,therewaslittleornodamagetothebuildingsandtheimpactontheoccupantswasnogreaterthanconcernsoversmallhairlinescracks.


Figure16.LabourersRebuildingtheWallsoftheRamayanaShoppingCentre,Padang.

The educational system in Western Sumatra had a two‐week hiatus as a result of theearthquake.Volunteersfromalocalactivitycompany(GALAPAGOS)informedus,itwasthegovernment‘s initiative for the schools to reopen after two weeks. Replacement schoolbuildingswereerectedaroundWesternPadang,andthesebuildingswereseenincountiessurroundingPariamanandPadang. TheUniversityofBungHattahadafewbuildingswithnon‐structural damage, but had achieved quick recovery and relocation of educationalfacilitiesandclassroomsbythetimeofsurvey.

Loss of documents, essential data, and equipment failure was another impact on theresidentsonWesternSumatra. Businessesandcommercial establishments that reliedonpaperdocumentationweregreatlyaffectedaslostinformationhadtobecollectedfromthebuilding rubble. In addition, sensitive equipment was also damaged as a result of theearthquake;forexample,mechanicalequipmentatPtSemenPadang(cementfactory)wasinitiallydamagedbuthassincebeenrepaired.

Temporaryfacilitieswereinitiallycrucialfortheoperationoftheessentialfacilities,andtheimpact of the earthquake on Western Sumatra’s essential facilities is still apparent.Extensivedetailsabouttheoperationandresponseof lifelineswillbediscussed in furtherdetail later in the report but a summary of how the response of critical facilities haveaffectedtheresidentsispresentedhere.

Thepoly‐clinic (outpatientgeneral clinic)of themainPadanghospital (Dr.M.Djamil)wasseverelydamagedby theearthquake, and immediatelyafter theearthquake, thehospitalemployeesmovedcurrentpatientsandredirectednewpatientstotemporaryfacilitiesset‐upinoutsidetents.Currently,duetotheseveredamagetothepoly‐clinic,thehospitalhas


redistributed theprospectivepoly‐clinicpatients to thecorrespondingdepartments in themainhospital,andthetemporaryclinicsarenolongernecessary.

Directly after the earthquake, residents went 10 days without electricity, one monthwithoutthecompleterestorationofthemainwatersupply(butwithwellaccess),andabout5dayswithoutmobilephonereception.Today,someofthetemporarywatertanksthatthewater companydistributedaroundWesternSumatraare still present (Figure17). Due tothedamagecausedtothewatercompany’smainbuilding, thewatercompanyhassetuptemporarymarqueesoutsidethemainbuildingasadministrativeoffices.Inaddition,smallphonetowerswithgeneratorswereset‐upthroughoutPadang(Figure17).

Figure17.WaterStorageTankataKuduGantingSchool(left)andTemporaryMobilePhoneTowerattheInnaMauraHotel(right).

Minimal information was gathered on the psychological impact and health of those notphysicallyinjuredbytheearthquake.TheGALAPAGOSvolunteersreportedthattherewasnooutbreakofdiseaseorillnessesinPadangasaresultofthelullinwatersupply;however,cases of diarrhoeawere common in residents in the counties near Pariaman. ThemainPadanghospital specificallynoted in their interviewthat theywerecounsellingpeople foranypsychological distresspromptedby theearthquake. Various conversationswith localresidentsconfirmedthatmostpeoplewouldnotbepersuadedtomovefromPadangasaresultoftherecentearthquake.

ResidentialResidentialbuildingsinthecitiesofPadangandPariamanmainlycorrespondtoone‐totwo‐storeyhighbuildingsconstructedofconfinedmasonry(Figure18).Duetothepredominant


hightemperatures in theregion,withayearlyaverageof27OC,housesusuallyhavehighceilingsforventilationpurposes;theroofsaretypicallycomposedofwoodframesontopofwhichcorrugatedgalvanisedironsheetsarefixed(Figure18,right).Inlow‐incomeareasorin small villages unreinforced masonry and wooden houses, or a mixed of masonry andwood,werealsoobserved(Figure19).Incontrast,wealthysectorsofPadangandPariamanhaveanumberofhousesconstructedofmoment resistant frameswith infillwalls (Figure19).

Figure18.Left:Typicalonestoreyhousemadeofconfinedmasonry(phototakeninPadang).Right:typicalconfigurationofresidentialroofs.

Figure19.Left:twostoreyhousemadeofmasonryandwood(Pariamancounty).Right:HouseinanaffluentareaofPadang.

In spite of the large number of residential buildings affected at different degrees (seeprevious section), severedamageor collapseof residentialhouseswasnotwidespread ineitherPadangorPariamancities.AdetailedsurveyofresidentialbuildingsintheregionwascarriedoutbyMapAction,anNGOspecialisedingatheringandmappinginformationaroundzoneshitbyanaturaldisaster.TheresultsofasurveyconductedbyMapActioninvariousareasofPadangCity(Figure20)showthatwidespreaddamage(i.e.where80%to100%of


householdsweredamaged,representedinthemapbydarkblueareas) isconcentratedinspecific parts of the city. However, even in these areas the proportion of houses heavilydamaged is ingeneralnotextensive;this fact isshownbythepiechartsateachsurveyedareawhereredcolourdenotesheavydamage.

AspuriouseffectofthemapinFigure20isthattheareasintheSouthernpartofthecity,identifiedwith40%to70%ofhouseholdsbeingdamaged(i.e.,areasinbluecolourtones),correspond to mountain areas not densely populated and where houses are mostlyconstructedalongtheshoreanduptotheskirtsofthehills.Thereforeeventhoughthemapproportionallyshowsasignificantpercentageofthecityhavingwidespreaddamage,mostoftheseareasintheSouthdonothavealargenumberofhouses.

The area of Padang city with higher concentration of households affected, as shown inFigure20,isalsoshownusingGoogleMapinFigure22.Asobservedinthelatterfigure,theareacorrespondstoaportionofthecitysurroundedbymountainswherepotential“basin”effectsmayhaveoccurred.Thishypothesisneedstobecorroboratedwithasoilmapofthecitythough.

Figure 21 shows the distribution of the intensity of the earthquake effects felt at thesurface, reported using theModifiedMercalli Intensity scale and data fromBMKG. BothPadangCityandPariamanCity(KotaPadangandKotaPariaman)reportedalevel7intensityor greater, describedas greater than “very strong intensity.” TheBMKG intensitymap iscomparabletointensityresultsproducedbyMapAction(basedondatafromtheIndonesianDepartmentofEnergyandMineralResources).ThecorrelationbetweenthedamagescalesofFigure20andFigure76andtheintensitiesinFigure21arenotexplicitlyexpressed,butcomparing the figures confirms the expected conclusion that a large percentage ofwhatMapactionandBNMPhasdescribedasseveredamagecorrespondstoVIIMMI.Similarly,verylittleseveredamagetohomesisseeninareascorrespondingtoVMMI.

SomeexamplesofdamageonresidentialbuildingsarepresentedinFigure23.


Figure20.HouseholddamagedistributioninareasofPadangCity(byMapAction,basedondatacollectedbefore21October).Theareawithextensivedamage,showninthemiddleof

themap,ispresentedinFigure22.


Figure21.Isoseismalmapforwestsumatraearthquake(BMKG,2009).

Figure22.GoogleEarth3DvisualoftheareamappedbyMapActionwith80%to100%ofhouseholdshavingadegreeofdamage.


Figure23.Damagetoresidentialbuildings.Top:householdsinPadang.Bottom:structuresinPariamancounty.

CommercialCommercial buildingsmainly consisted of one to two storey structures. Most businesseswereeithersmallorfamilybusinessesandledtothestructurebeingofmixedcommercialandresidentialuse(i.e.thegroundfloorwasusedforcommerce,whiletheupperfloorwasresidential).

Larger companies, head offices, and hotels ranged from 2‐6 storeys and were usuallyreinforcedconcreteframeswithmasonryinfill.

China Town. The region shaded in blue in Figure 24 is the China Town in Padang. Theconstruction in this region was particularly poor and many small buildings were badlydamaged. This is themainmarket forPadangand foodsuppliesweredisruptedduetoahigh proportion of the buildings failing. The building typology often consisted of


unreinforced masonry (without reinforced concrete frames). The major failure mode ofthese buildings was collapse of external walls. In the case of buildings that did havereinforced concrete frames, the columns were often 150mm x 150mm. These generallyfaredbetter;howeverthecolumnswereofteninsufficient.

Figure24.TheChinaTown(shadedinblue)andCentralRegion(shadedinyellow)inthecityofPadang.

Centralregion.Themajorityofbuildingsinthisregion(shadedinyellowinFigure24)weregreater than two storeys and were reinforced concrete frames with masonry infill. Theperformanceofthebuildingswasveryvariable,withdamagerangingfromminorcrackingofmasonry infill to total collapse. The majority of buildings suffered at least significantcracking in the masonry infill panels. Few structures had either no cracking or minorcracking. The masonry infill was often observed to have fallen out of the frame. Themajorityoffailuresinthestructuralsystemofthebuildingswerethedevelopmentofplastichinges inthetopsandbottomsofthecolumns(softstorey failure)asshowninFigure25.Minor crushingof concretewasoftenobserved in the topsof the columnsoftenwithoutsignsofdistressinthebottomofthecolumns.Strongbeam‐weakcolumndesignswerealsoobservedinvariouscommercialbuildings,aswellashospitals.AccordingtotheUniversityofBungHattaengineers,theprincipleofstrongcolumnandweakbeamhasyettobefullyadoptedbydesigners intheregion. Partialor totalcollapseofengineeredstructureswasevidentinmanylocations.Oftentheseweregovernmentbuildings.


Figure25.Plastichingingatcolumnendsofreinforcedstructure.

Hotels. Thereweremanymulti‐storyhotels in Padang,with ahigh variability of damageranging fromcompletestructural collapse toonly secondaryelementsdamaged. Mostofthe hotels were constructed within the last 30 years. Shear cracking and failure of themasonryinfillwasalsotypicalinthedamagedhotelbuildings,similartothedamagenotedin the smaller commercial buildings. Soft‐storey failureswere common, as seen inHotelHayamWuruk,asmallhotelincentralPadang,abeachhotel,andtheInnaMauraHotel,ahigh‐classhotel incentralPadang(Figure26andFigure27).ThefailureoftheInnaMaurahotelwasunique,asthemajorityof thehotelhadonlyminorstructuraldamage,butonewing suffered extreme damage. A lack of transverse reinforcement at the beam‐columnjointswasobserved(Figure28)


Figure26.ExamplesofSoft‐storeyHotelFailures.Top:HotelHayamWuruk.Bottom:BeachFrontHotel.


Figure27.Soft‐storeyfailureoftheInnaMauraHotel.

Figure28.Evidenceofsoft‐storeyfailure,light‐fixtureandchairatgroundlevel(left)andlackoftransversereinforcementinbeam‐columnconnection(right).

Damagetothehotelsdidnotseemtocorrelatetotheageofthebuildingorclientaffluence.Forexample,theAmbacanghotelandInnaMaurahotel,bothmulti‐story,expensivehotels,suffered major damage. The Ambacang hotel was the most severely damaged hotel


observedduringthesurvey (Figure29). TherewerealsoaccountsthatproperevacuationplansoftheAmbacanghotelwerenotavailablewhentheearthquakeoccurred,resultinginnumerous fatalities. TheAmbacanghotelwas unusual as itwas primarily a steel framedbuildingwiththeconcretefloorsbeingconstructedwithprofiledsteelsheeting(thiswastheonly significant steel framed building observed by the team). It appears that there wasfailureofthesteelbeamsandreinforcedconcretecolumns;however,acompletesurveyofthebuildingwasnotpermittedduetothenegativepublicitythehotelreceivedbecauseofitspoorperformanceduringtheearthquake.

Figure29.AmbacangHotelDamage.

In some cases, there was little to no structural damage of the multi‐storey hotels. TheBumiminanghotelexperiencedmasonrydamagebutnoobviousprimarystructuralfailure.False masonry “columns” (two adjacent masonry walls) were also damaged, but thereinforcedconcretecolumnsappearedundamaged(Figure30).TheextensionofthebeamspasttheexteriorofthecolumnsdepictedinFigure30islikelytobeaseismicratherthananarchitecturaldetailand indicates that thisbuilding is likely tohavebeenconstructedwithgoodseismicpracticeinmind.Thestronggroundshaking(evidencedbythefailedmasonryinfills)andthelackofobviousstructuraldamagesuggeststhatthisbuildingandtheseismicpractices employed have worked well. However, the teamwas informed that the hotelwouldbedemolishedandnotrepaired. It is likelythatthedecisiontonotrepair isduetodamage to architectural elements inside the building as well as the obvious externaldamage,butthiscouldnotbeconfirmedasaccesswasrestricted. TheBaskoGrandMall,recently constructed and owned by the Western hotel chain – Best Western, had noapparentstructuraldamagefromanexteriorsurvey.Theonsiteguardswouldnotpermit


aninteriorsurvey,butitwasconfirmedbyahotelassociatethatthehotelhadclosedduetodamagetoarchitecturalelements.

Figure30.BumiminangHotel,shearcrackinganddamagetofalsemasonrycolumns.

Seismicdetail


ShoppingCentres.Similarly,thesamevariabilityofdamagewasnotedinshoppingcentres,which were also reinforced concrete frames with masonry infill. Two large shoppingcentres,theRamayanaShoppingCentreandtheBaskoGrandShoppingCentre(adjacenttothehotel),andahandfulofsmallershoppingcentresweresurveyed.Soft‐storeyfailurewasobserved inoneof thesmaller shoppingcentres, theNelayanRestandCaféCentre. Thisstructure was adjacent to the Samudera Jaya shopping centre, which had little to nodamage(Figure31).

Figure31.SmallShoppingCentres;Left:soft‐storeyfailure,Right:Minimaldamage.

TheBaskoGrandShoppingCentrehadnonoticeablestructuraldamagefromtheexterior,and it is alsoa very recent construction (Figure32).However, similar to theBaskoGrandHotelnextdoor,theshoppingcentrewasclosedimmediatelyaftertheearthquake.

The Ramayana shopping centrewas a large four‐storey structure. Damage caused by firewasnoticeablealongasectionneartheroof,andconstructionworkerswerebeginningthereconstruction of the masonry walls. It appeared that the masonry infill walls hadcompletely failed, although the primary reinforced concrete columns were robust andsuffered no obvious damage. Narrow columns supporting the roof cantilever failed.


Different construction techniques were being implemented for the reconstruction of themasonry infill. The concrete confining columnswere placedmore frequently, likely in anattempttoprovideadditionalsupportforthemasonrywalls.SeeFigure33andFigure34.

Figure32.Shoppingcentrewithlittletonostructuraldamage.

Figure33.RamayanaShoppingCentre(left)androofcolumnfailures(right).


Figure34.RamayanaShoppingCentre:firedamage(left)andnewmasonryconstruction(right).

Theextensivedamage tohotels and shopping centres,whichwereusually insured, is thelikelyexplanationfortherelativelylargeratiobetweeninsuredandtotal(ground‐up)lossesforthisevent.Thisisparticularlytrueconsideringthattheearthquakewasnotdevastatingfortheresidentialbuildingsorsmallercommercialbuildings(usuallyuninsuredbuildings).

GovernmentBuildingsAccordingtoseniormembersoftheBungHattaUniversity,about80%ofallgovernmentalbuildings in Padang were severely damaged or collapsed. One of the reasons for thisbehaviourwasexplainedastheageofmostgovernmentalbuildings,meanttheyhadbeendesignedandconstructedtotheolddesigncode.Inthelattercode,thegroundmotionsfordesigncorrespondto200yearsreturnperiod,incontrasttothegroundmotionsfordesignfromthenewdesigncode(SNI‐1726‐2002)thataresetatareturnperiodof475years.

ThenumberofbuildingsinWestSumatrathatweredesignedaccordingtothe2002ortheformerearthquakestandardcouldnotbeclearlyidentified.Thereasonsforthisisthateventhoughthelatestcodewasinitiallyreleasedin2002,ittookafewyearsbeforethecodewasadoptedbythelocalengineers.Asaresult,thereisnoguaranteethatthestructuresbuiltafter2002weredesignedaccording to thenewearthquake code. Secondly, lackof codeenforcement by either the Indonesian government or relevant building authorities hascontributed to the inappropriate application of the seismic and building standards inconstructionpractices.

The observed Governmental buildings in Padang are constructed of reinforced concretewith moment resistant frames and infill walls. Most of the damage observed in thesebuildings was caused by soft storey failures. A typical example is presented in Figure 35wherethedifferencesinrigiditybetweenthegroundfloorandthefloorsabovearesevere.OtherexamplesofstructuralfailuresofgovernmentalbuildingsareshowninFigure36.The


roofs of the buildings in the latter figure reproduce the shape of typical constructions inWestSumatra;initiallythoughttobeveryheavyroofsandthusacontributingfactortothedamageobserved, they are actually less heavy than the concrete slabsobserved inotherbuildings.

Even though the construction of governmental buildings requires the supervision of thecorrect implementation of the design specifications, some quality faults (such as lack ofenough reinforcement and the use of plain reinforcement bars contrary to ribbed bars)wereobservedduringthesurvey.

Theuseof inappropriatedesigncodesandpoorqualityofconstructionmaybethemajorcauses of damage to governmental buildings in Padang. A governmental building inPariaman(closertothefaultrupture)thathadaverygoodstructuralbehaviourispresentedinFigure37.


Figure35.SoftstoreyfailureofagovernmentalbuildinginPadang,withthebottomphotographshowingthefailureofthecolumnintheareaindicatedintheupper

photograph.

PostEarthquakeFieldInvestigationoftheM7.6PadangEarthquakeof30thSeptember2009 Page38

Figure36.ExamplesofsoftstoreyfailuresingovernmentalbuildingsinPadang.


Figure37.GovernmentalbuildinginPariamancity.Inspiteoftheirregulargeometryofthebuilding,theobserveddamagewaslimitedtothetwoinfillwalls.

IndustrialBuildingsIndustrialfacilitiesinPadangareprimarilyconcentratedintheSouth‐easternpartofthecityandtheareaclosetothePort,intheSouthofPadang.

TheEEFIT teamvisited the local cementplant (Figure38) that, according to itsmanagingdirector,provides90%ofthecementtotheprovinceofWesternSumatraandabout50%toallofSumatra.TheyalsoexportcementtoMalaysiaandSingapore.Itistheoldestcementfactory in Indonesia (founded in 1910) and directly employs about 2,000 people plus asignificantnumberofpeopleindirectly.

Fromthestructuralpointofview, theonlyproblem in the factorywasaveryminor issuewitha reinforcedconcretecolumn that lostpartof theexterior concrete (Figure39).Themostseverestructuraldamageinthecomplexoccurredtoaonestoreyhighbuildingmadeofconfinedmasonrythatwasusedforadministrativepurposes.Thisbuildingsufferedthecollapseofacoupleofinfillwalls,thoughmostofthebuildingonlysustainedslightdamage.

In spite of the practically nonexistent level of structural damage in the factory, theproduction of cement stopped completely for seven days. The principal reason for thiscorresponds to the lackofelectrical supply fromthemainnetwork; theplanthas itsownpowergenerator,thoughitwasnotfullyfunctionalatthetime(personalcommunication).Additionally, some equipment had to be stopped for reparation since some mechanicalproblemsoccurred.Theplantpersonnelwerebacktoworkfourdaysaftertheearthquake,andproductionwasresumedatnormallevelsamonthaftertheevent.


Figure38.Twoareasoftheproductionlineofthecementfactory(fromatotaloffivelinesofproduction).Nostructuralproblemswereobservedduringthevisit.

Figure39.AminorproblemwithaRCcolumninthecementfactorywherepartofthefaceconcretewasdamagedandthenrepaired.Thisdidnotrepresentastructuralproblem.


ThecementproducedinthefactoryisdistributedandexportedthroughPadangport.Sinceoneofthecranesdedicatedtouploadthecementcollapsed(therewereexclusivecranesattheportforloadingthecement),thedistributionofcementwasfurtherreduced.Anotherfactorthatreducedtheproductioncorrespondstomachineryinthemines(locatedatabouttwo kilometres southward from the plant) having some degree of mechanical damagecausedbytheearthquake.

Allinall,itcanbestatedthatthecementfactorystoppedproductioncompletelyandthenhad a reduced capacity not because of structural damage resulting from the earthquakeground motions but because of the interruption of the electrical supply and machineryproblems.

A second industry visited during the surveywas a rubber plant that exportsmaterials tosome neighbouring countries and the United Arab Emirates (Figure 40). The plant wasconstructedaround1982andisareinforcedconcreteandsteelstructure.Theplanthaltedproductionfor tendaysbecauseofdamagetothereservoir that filtersoutthepoisonousby‐productofrubberproduction(Figure41).Afterthetankwasrepaired,theyresumedtherubberproduction.

Otherinstallationsthatwereaffectedduringtheeventwerethewarehouse,thelaboratory,thestaffhousingandtheelectricalgenerator,allofthemhavinglighttomoderatedamage.Machineryintheplanthadtoberecalibratedbutwasnotdamagedduringtheevent.

Figure40.RubberplantinPadang.


Figure41.Damagetothereservoirwherepoisonousmaterialsareremovedbeforedisposalofresidualwaters(photosprovidedbytheplantmanager).

EventhoughtheEEFITteamvisitedalimitednumberofindustriesinPadang,itseemsthatnoneof the industrial facilities suffered significant structuraldamage.However, industrialactivitiesinthecitywereseverelydisruptedduringthefirst7to10daysduetofailuresinthe electrical power supply, and then afterward due to repairs and recalibration ofmachinery.

PortfacilitiesPadang has an international port which is the most important in the West Sumatranprovince. Access to the port was restricted and security was under the control of theIndonesiannavy.Accesswasfinallygrantedandanassessmentofthefacilitiesconducted.

Nostructuralproblemswereobservedinanyoftheportelements(Figure42), includingalight steel structure and the warehouse made of reinforced concrete moment resistingframeswithinfillwalls.Theexceptionwasthecollapseofacranewhoseprincipalfunctionwastheuploadingofcementfromtheplant(allelementshavebeenremovedatthetimeofthevisit,thusnopicturesweretaken),andthesettlementofabout60mmoftheaccesstothedockstructure(Figure43).

Figure42.Nostructuraldamagewasobservedinanyoftheportfacilities.Left:lightsteelstructure.Right:warehouseofRCmomentresistantframeswithinfillwalls.


Figure43.Settlementoftheaccesstothedock.Maximummeasuredsettlementswere60mm.

SchoolsSchools were among the most affected facilities after the West Sumatra Earthquake.AccordingtoNationalDisasterMitigationAgencyRepublicofIndonesia(BNPB2009),thereare2,164schoolsseverelydamaged,1,447moderatelydamagedand1,137lightlydamagedinWestSumatra,concentrated inPadangCity,PadangPariamanandAgamCounty (Table4).

Table4.SummaryofDamagedSchoolsAfter30September2009Earthquake(BNPB2009).

DamagedLevelNo. REGION

Severe Moderate Light

1 PadangCity 1,606 1,038 903

2 PariamanCity 92 101 22

3 PadangPariamanCounty 257 87 31

4 AgamCounty 114 77 65

5 PadangPanjangCity 23 41 26

6 SolokCounty 3 36 28

7 PasamanCounty 1 ‐ 13

8 PasamanBaratCounty 27 16 1

9 PesisirSelatanCounty 29 43 34

10 BukitTinggiCity ‐ 6 8

11 SolokCity 3 ‐ 2

12 TanahDatarCounty 5 ‐ 4

13 MentawaiIslandCounty 4 2 ‐

TOTAL 2,164 1,447 1,137

TheEEFITteamsurveyedvariousschoolsinPadangandinthedistrictofPariaman.Mostofthe schools surveyed were government schools, which typically imply less funding for


construction. The primary mode of failure of these buildings was poor constructiondetailing.Rooffailureswerecommonduetoinadequateconnectiondetails.Insomecases,thecollapseortiltingoftheentirewallswasobserved.Theconstructiontypologyofmostof the schoolswas improperly confinedmasonrywith timber framingand roofs. Mostofthe schools were comprised of numerous, rectangular‐plan, single‐storey buildings withconcrete slab foundations. Some of the school buildings had very narrow concretecolumns,whileothershadnot. Ineithercase,it isexpectedthatinsufficientsupportwasprovidedforthemasonry.TheIndonesiancoderequiresreinforcedconcretecolumnsat3mspacing to confine masonry walls (maximum area of each sequence of masonry wallsuggested 12 m2). This level of confinement was rarely noted in the school buildings.EngineersattheBungHattaUniversity inPadangattributedtheschoolbuildingfailurestothelackofconstructionsupervision.

AccordingtothevolunteercoordinatoratGALAPAGOS,numerousschoolsinPadangweredamaged, and seventy‐percent of the schools in the Pariaman district were destroyed.Pariamanisonly31kmfromtheearthquakeepicentre.TheIndonesiangovernmenthadaninitiativeforschoolstoreopentwoweeksaftertheearthquake,andthiswassuccessfullyimplemented. Temporaryschoolbuildingswereconstructedoutsidewithtimber framingand a steel corrugated room, and these temporary school buildings are currently beingused.

Of the two school buildings comprising the SDN 24 Ujung Gurun elementary school inPadang, one building completely collapsed and the other suffered shear‐cracking. SeeFigure 44 and Figure 45, respectively. The structural typology was masonry with verynarrow reinforced concrete columns at the wall joints. The roof was timber withcorrugated sheet metal. The collapse of the building may be attributed to a lack ofmasonry confinement in the walls, poor or no connection between adjacent walls, anextremely shallow footing, and insufficient concrete reinforcement. It seemed that thecollapsed building had a long segment ofwall thatwas not supported by the crosswall(only500mmhigh)orthetimberrooftrusses.Asaresult,theouterwallhadnosupportandthereforetheinertiaforcefromthewallcausedoutofitsplanetoppling(i.e.itsweakdirection). Themasonrywallsareconstructedas separatepanelsbutnotproperly tiedtogetheratthewalljoints,makingthewallssusceptibletotiltingandcollapse(Figure46).


Figure44.SDN24UjungGurunElementarySchoolinPadang–collapsedbuilding.

Figure45.SDN24UjungGurunElementarySchoolinPadang–less‐damagedbuilding.

It is unclearwhyonly oneof the SDN24UjungGurun school buildings collapsed, as themodeofconstructionandageofthebuildingsappearedidentical.However,manyfactorsmayhavecontributedtothesurvivalofthe lonebuilding, including increasedsupportforthe cantilevered roof as provided by the timber columns (not present in the collapsedbuilding)ormoreattentiongiventoconstructiondetails.

The Yayasan Payoga SD Agnes elementary school, a private school in Padang, was alsosurveyed. IncontrasttotheSDN24UjungGurunelementaryschool,themasonrywalls inthisbuildingwerewellconfinedandthewallssufferedonlyshearcracking.Theschooldidsufferaroofcollapsehowever,possiblycausedbytheheavyrooftiles(Figure47).

DirectionofEarthquakeShaking


AdditionalschoolsweresurveyedinthedistrictofPariaman,includingaschoolinthesmallvillageofKuduGanting, twoschools inPariaman,andtheremainsofaschool foundationwere found in the landslide rubble of Kapolo Koto. Refer to the geotechnical section formoredetailsabouttheKapoloKotoSchool.

Figure46.Locationofwalltowalljoint–noconnectionbetweenorthogonalwalls.

Figure47.HeavyclayrooftilesfromtheYayasanPayogaSDAgnesschool.


TheSDN01LimaKotaTimurelementary school,agovernment school inPariaman,hadasimilar structural typology to the Padang schools, without reinforced concrete cornercolumns.Theunconfinedmasonrywallsseemedinsufficientlyjoined,anditappearedthattheroofandwallscollapsed.Therewasnoanchoragefoundattheconnectionbetweenthebearing wall and the roof truss structure, indicating that the roof construction was notappropriatelysupportedinthehorizontaldirection(Figure48).Asaresultthelateralforceoftheearthquakelikelycausedtheroofconstructiontodisplaceandfail.

Reconstructiononthisschoolbuildinghadalreadybegun,andthereplacementbrickswereeitherbricks salvaged fromtheearthquake,ornewbricksof thesameexceptionallypoorquality(thebrickscouldbeeasilycrumbledbyhand).Thelocalresidentsshowedtheteamthetemporary,timberschoolbuildingfurtherdowntheroad(

Figure 49). Other schools in Pariaman had initiated demolition of the severely damagedbuildingsandstartedonreconstruction. Itmaybemoredifficulttodifferentiatebetweentheearthquake‐inducedschooldamageandthebuildingdemolitionduetothetimeelapsedsincetheearthquake(1month).

Figure48.SDN01LimaKotoTimur,anelementaryschoolinPadangPariamanCounty.

AB

DetailB


Figure49.SDN01LimaKotoTimurtemporaryschoolbuildings.

HospitalsThe team surveyed three hospitals. The first was The Bunda Medical Centre a privatehospital in the centre of Padang, The Dr.M. Djamil General Hospital, which is themainhospitalinPadangandthereforethemainhospitalinWesternSumatra,andthethirdwasthe localhospital forPariaman. All threehospitalswere concrete framed structureswithmasonryinfill.

TheBundaMedical Centre had suffered serious damage,withmajor structural failures inmanycolumns(Figure50)aswellasextensivedamagetomasonryinfillpanelsandwindows(Figure51).Thefailedcolumnswereconstructedofroundsmoothbars,with8mm*smoothconfiningreinforcementatapproximately150centres (*lackofaccesspreventedaccurateassessment).Atthetimeofthesurveythehospitalwasoutofactionandrepairhadstarted.


Figure50.BundaMedicalCentre.

Figure51.BundaMedicalCentreshowingextensivecrackingofnon‐structuralmasonry.


TheDr.M.DjamilGeneralHospital isareasonablymodernfacilitydealingwithallmedicalcomplaints. It has an 800 bed capacity and an outpatient unit that can deal with 1200patientsperday.Thestructureofthehospitalconsistsofmanymedicalunitshousedinanumber of buildings. These structures are typically reinforced concrete frames withmasonryinfill. Ofthesebuildingsonlyone,thePolyclinic(outpatientward)collapsed(seeFigure 52). Of theother buildings, none sufferedmajor structural failure; however therewas somenon‐structural damageandwidespread failureof themechanical andelectricalservices.Someoftheseserviceswereterminatedbecauseofexternalinfluences(e.g.waterandelectricitysupplytothehospitalwascut)whileotherservicesfailedduetodamagetothemechanicalandelectricalcomponentsofthesystem.

a) Polyclinic b)failedConnectiondetailinPolyclinic

Figure52.Dr.M.DjamilGeneralHospitalPolyclinic

The team interviewed representatives of the hospital consisting of public relations staff,administrationstaffandmedicalstaff.

At the time of the earthquake the hospital had 430 patients, which was well below theaveragebedoccupancyof600beds.Manypatientspanickedinresponsetotheearthquakeand tried to leave. Thehospital hasevacuationprocedures andanevacuation routeandpatientswereevacuatedusingtheseroutes.Criticalpatientswerealsoevacuatedwiththeassistanceofhospitalstaff.


Onehour after theearthquake, 14 tentswith a capacityof 25people/tent and2 surgerytentswereerectedusingthehelpofthestaffofthehospital,theDepartmentofHealth,RedCrossPadang,theSocialDepartmentandtheArmedforces

Onthefirstday70peoplewithinjuriesrangingfromminortosevereweretreatedinthesetents;40patientswithminorinjurieswereuntreatedduetolackofcapacity.Somepatientswithminorailmentsalreadybeingtreatedatthehospitalweresenthomeearly. Thevastmajorityofinjurieswereheadinjuries,crushinginjuriesandfractures.

Althoughtherewassomedamagetothehospital,thehospitalcouldstilltreat800patients(theusualcapacityofthehospital).Theonlymajorstructuralfailureinthehospitalwastheoutpatientbuildingwhichhadcompletely collapsed. Thisbuildinghadacapacityof1200patients/day.Thepatientsthatwereusuallytreatedbythisunitwereeithertreatedinthetents or in the appropriate inpatient unit of the hospital. At the time of survey, thepolyclinicwasstilloutofactionandsooutpatientsweretreatedbytherelevant inpatientunits.

Mostof thededicatedhospitalmechanical serviceswerebroken. For example thepipedoxygenwasbrokenandsomobileoxygenunitswereused. Theseprovedtobeadequateforthedemand.

Thehospitalwaswithoutpowerfor3days,andthereforereliedondieselgenerators.Thetotal capacity of the generators is 25 MW. The usual requirement for the hospital isapproximately 100 MW. The diesel generated electricity proved adequate to supplyelectricityforcriticalservices.

Theearthquakeleftthehospitalwithnomainssuppliedwater.Thisresultedininsufficientwater for thepatientsand forcriticalhospitalprocedures. Theonsite reserves thatwereavailablewerecarriedtothepatientsinthetentsandrationed.

Aftertheseconddaywaterarrivedbytruckandthiswaspumpedtowhereitwasneeded.Thishelpedtorelievethewatershortage,butwatersupplywasstillcritical.

About20%ofthestaffweredirectlyaffectedbytheearthquake(eitherlosstheirhomesorinjuries torelatives)butnoneof thestaffwereactually injured. Themaindirectorof thehospitaldirectedexistingstafftostayatthehospitaltotreatpatients. Thehospitalhasastaff of 200 doctors and 800 supporting staff and all made themselves available. Thisresultedinnoissuesduetostaffshortages.

The deceased that were brought to the hospital were treated using Disaster VictimInvestigation (DVI). This is a basically an identification and autopsy procedure. Once thisprocesswascompleted, familieswouldcollect thecadavers forburial.Thecapacityof themorgueis12x3bodies.36bodieswereprocessedonthefirstdaywithatotalof135being


identified. Body identificationwas conducted by the DVI team, the police and the NorthSumatraProvincialGovernment.

Several other hospitals were severely affected by the earthquake, some of which wereeitherbadlydamaged,didnothavethecapacitytocopeorthespecialistunitstodealwiththecasualties. Allhospitalscoordinatedandpatientswerestabilisedandthentransferredfromoutlyinghospitalstothishospital.

Thetotalnumberofcasualtiestreatedinthetemporaryhospitalwas366,with200oftheserequiring surgery and 1983 casualties were treated as outpatients. Patients were alsoofferedpsychologicaltreatmentstohelpdealwiththetraumaoftheevent

Outsideaidstartedtoarriveonthesecondday.Initiallyaidfromotherpartsoftheprovincearrivedonthesecondday,withthefirstNGOsandotheroverseasaidorganisationsarrivingonday4andthemajorityhavingarrivedbyday5.

Hospitalstaffreportedthatallaidwasveryhelpfulandrelievedalotoftheextrapressurethathadbeenputon thehospital, but ithadmainly relieved thepressureandallowedabetterofstandardofcaretononcriticalandcriticalpatients,ratherthanbeingessentialforcriticalpatients.

People were returned from the temporary hospital setup (tents) in the grounds of thehospital after thirdday. By the fourthdayallpatientshad returned to themainhospitalbuildings.

ThehospitalinPariaman,althoughmuchclosertothefault,sustainedvirtuallynodamage.Theonly visibledamagewasminor cracking tonon‐structuralmasonry. Thehospital andcrackingonthemasonrywallscanbeseeninFigure53

Figure53PariamanHospital


LIFELINES

WaterSupplyPadang is serviced by only one water company called Perusahaan Daerah Air Minum(PDAM) which supplies 64,000 customers in the city. The Team visited the local waterCompanyandinterviewedtheengineersandthetechnicaldirectorofPDAMPadang.

The PDAM has three main reservoirs and associated trunk mains and a number ofboreholes.ThethreereservoirsareLubukMinturun,supplyingtheNorthzonewith290l/scapacity;UluGadut,supplyingtheSouthzonewith220l/scapacity;andGunungPangilun,supplyingthecentralzone,whichhasacapacityof500l/s.Thecapacityoftheboreholesisapproximately90l/s.Alltrunkmainswere600mmindiameter.

Immediatelyafter theevent, themaintrunk for thecentralPadangregionwassevered intwoplaces,resultingintotallossofits500l/ssupply.Thedistributionnetworkofthewaterwasalsodisruptedduetothepipedamages.Asthepumpsfortheboreholeswerepoweredbyelectricity,thissupplywasalsoterminated.Thiscausedthelossof85%oftheboreholeservice and effectively left the central regionwith nowater. The damages to thewaterfacilitiesimmediatelyaftertheearthquakearesummarizedInTable5:

Table5.Damagetowatersupplyfacilities.

No. DamagedFacilities DamagedDetails DirectImpact1. Ground settlement (20‐30cm)

at water treatment facility inGunungPangilun

‐ Tilted2unitofaccelerator‐ Brokeeffluentacceleratorpipesandeffluentfiltrationunit

‐ WaterTreatmentFacilitywasshutdown

2. SupportingFacilities/

Buildings‐ PowerHouse‐ Chemicalandwatercontrolbuilding

‐ HeadOfficeandTheNorthBranchOffice

‐ Noback‐uppower/electricityforpumpingthewater

‐ Unsettlingadministrationsystem

3. LeakofPipes

‐ TransmittingPipes(DN500mm)‐ PrimaryDistributionPipes(DN400mmand600mm)

‐ Secondary,tertiaryandservicePipes

‐ Watersupplyhadbeendisrupted30%,butnotaffectedthewaterproductivity

4. WaterIntakeinSikayanandUluGadut

‐ Lossof220l/swatersupply ‐ Failedtoserve±20,000customers

Chronologyofthesituationaftermathwasdescribedasfollows:

Day1:Thefirstdayaftertheearthquake,waterfromtheothertworeservoirswasdivertedto the central region and in particular the hospital; however network failuremeant littlewatergotthrough.Thewatercompanyhadtwo,4m3watertruckswhichwereimmediatelymobilised to supply water to theM. Djamil Hospital (themain hospital in Padang). Re‐establishingmainswatertothehospitalwassetasthehighestpriority.


Day 2: On the second day after the earthquake, the water company had started theemergency response program. It obtained another three, 5m3 water trucks from TheDepartmentofCivilWorksofWestSumatra.Inadditiontotheextrawatertrucks,108unitsof 2m3 water storage tanks were provided which allowed distribution to other areas ofcentralPadang(seeFigure17).

Day3:Day3sawthearrivalofanother9trucks(5m3)fromneighbouringregionssuchasJambi,Solokandothers.Otherwitnessreportsstatedthatthehospitalwasseverelyshortofwateruntilthisday.

Day4and5:OSandNGO’sarrivedonthesedaysbringingafurther49trucks.Thesetrucksweresuppliedbyshipandbyair,theAustralianarmyalsoprovided2reverseosmosisunits,forthedesalinationofseawater.

Day5and6:Localresidentsrioted,attackingthemainheadquartersofthewatercompanyandthedepartingwatertrucks. Thiswas inresponsetohavingnowaterfor5days. Theintervieweestatedthatprogresswashamperedbymanystaffhavingtohelptheirfamiliesintheaftermathoftheearthquake.

Day 10: The repair of the trunk main occurred on this day. This coincided with theresumptionoftheelectricalsupplyandthereforethepumpingstationcouldoperate. Thewater company had two diesel generators; however these had insufficient capacity,therefore if the trunk main had been repaired earlier it would not have resulted in asignificant increase in supply. Theother reservoirsweregravity fedand therefore lossofelectricityhadnotresultedinlossofsupply.

Tomitigatethewaterproblems,thecompanysuggestedthefollowingactions:• Carryoutinventoryofdamagedassets/facilities.• Buildtemporarysheltersonparkingareaattheheadofficetoaccommodate

administrationactivitiessincethemainofficebuildingshadbeenseverelydamaged.• EstablishWaterSuppliesEmergencyPostincollaborationwiththelocalgovernment

tosupplywatertothepublicbyusingtrucksandhydrants.TheallocationofwatertrucksandhydrantswasbasedonpriorityinconjunctionwiththeDepartmentofCivilWork(PUCiptaKarya)andUNICEF.

• LaunchEmergencyResponseTeamtodealwiththerepairofwaterdistributionnetworkandasset/infrastructures.Thenumberofrepairteamsbeforetheearthquakewas4andhadbeenincreasedinto14afterwards.Additionalexternalsupportingteamscontributedbynationalandlocalcontractorswerealsoinvolvedtospeeduptherecoveryprocess.

• Giveassistancetothecommunityincludinggettingfeedbackfromthecustomersandcollectinginformationtobetterdistributewaterusingthewatertrucks.


By November 8, 2009, thewater company had repaired 2300 broken connections in thedistribution network, but still had not returned supply to everyone. The distributionnetworkconsistsofductile cast iron,asbestoscementandPVC. Itwas reported that thevastmajorityofthefailureswereintheconnections.Thetechnicaldirectorsuggestedthatmorefirehydrantswouldhavebeenuseful,asitwouldhaveimprovedpostdisastersupply.Resuming serviceswas being hamperedby difficulty in finding leaks. Leak detectionwasconducted by flushing pipes with water, which was difficult to justify in an alreadyoverstretchedwatersupplysystem.

Allreservoirshadbeenundamaged;howeverthewatertreatmentworkssuffereddamageduetosettlementresultinginanintermittentabilitytotreatthewaterthatwasstillanissueatthetimeofsurvey.

TransportNetworksIn Padang city, transportation networks received little damage from the earthquake. Novehicular bridges were reported as unfit for passage and few roads were closed. Nosignificantsignsofdamagetobridgedecks,displacementofspansatthejoints,norspallingof concretewere observed. Failurewas however observed at aminor road by the coast.Figure 54 shows the settlement of road due to the loose soil condition at the subgradeundertheearthquake’scyclicloading.ThetensioncracksparalleltothecoastlineinFigure55maysuggest thepossibilityof lateral spreadingarising fromtheeffectsof liquefaction.Thesecrackswereparticularlyfoundattheedgesandmidwayoftheasphaltpavement.Theformerwaslikelyduetothechangeinstiffnessduetothediscontinuityofmaterial,whilethelattermayhavebeencausedbythepresenceofconstructionsequenceofthewearingcourse. The settlementsmeasuredwereup tohalf ametredeepand the crackwidthsof150mmwidestretchingformorethan10metreslong.

Figure54.Settlementandcracksonroadparalleltothecoastline.

Severesettlementofroad


Figure55.Tensioncrackspropagatingparalleltothelongitudinalaxisoftheroad.

SeverefailurewasalsoobservedatthecrestofaslopingroadasshowninFigure56.Thismayhavebeenduetosettlementofloosesoilbeneaththeroad.Heavingwasnotobservedatthetoewhichruledoutthelikelihoodofaslipfailure.

Cracksparallel to theplaneof fault rupturewerealso sighted inanopencarparknearastadiumasshowninFigure57.

Figure56.Severefailureofroadatthecrestoftheembankment.


Figure57.Roadcracksparalleltotheplaneoffaultrupture.

InthedistrictofPariaman,landsidesandslopefailuresdidcausedisruptiontoroadsandapedestrian bridge, with a number of roads becoming impassable. Although these roadscouldbeconsideredtobeminor intermsoftheirconstruction, inanumberofcasestheyweretheonlyvehicularaccesstovillagesandthiscauseddifficultiesinprovidingaidtolocalpeople(seeLandslideandDisastermanagementsectionforfurtherdetails).

TelecommunicationTherewasonlyminor lossof service in landlines;however themajorityofmobilephoneswereout for10days.Thiswasdueto80%ofmobilephoneprovisionbeingmadebyonetelecomscompany.Thiscompanyhadno(orasmallamount)ofgeneratorsfortheirmobilephone masts. Connection was re‐established using transportable masts with their owndieselgeneratedpowersupply.


GEOTECHNICALASPECTS

FoundationFailuresFoundationfailureswereminimalinPadang.Thefoundationsofbuildingsaremostlyintactwithsomeminorsettlement.Oneof theuniversitybuildings inUniversitasNegeriPadangfoundedonpileshadsufferedslightdifferentialsettlements.This ledtosubstantialcracksandsettlementsinoneoftheadjoiningclassroomsasshowninFigure58.

Figure58.Crackonfloortilesofclassroomduetodifferentialsettlement.

Thefoundations,however,mayhavebeenlocatedonstiffersoil,whichthereforeresultedinminimalstructuraldamage.Figure59illustratesthesettlementofthesurroundingsoilofapproximately100mmrelativetothepilefoundation.CoarsesanddepositswerefoundinthisareaasshowninFigure60.

Figure59.Settlementofsoilaroundacolumnofauniversitybuilding.


Figure60.Coarsesandgrainsfoundwithintheproximityoftheuniversitybuilding.

Elsewhere,anelementaryschoolhadsufferedatotalcollapseofasegmentofitsone‐storeyclassroom building. One of the factors leading to the collapse was the insufficientembedmentofthewallintothestripfoundationasillustratedinFigure61.

Figure61.Wallcollapseduetoinsufficientembedmentofstripfoundation.


LandslidesTheteamvisitedthedistrictofPariaman,about50kmnorthofPadang,toinvestigatethenumerouslandslidesthatwerereportedinPariaman’ssurroundingvillages.Table6showsthe fatalities due to landslides which occurred as a direct result of the September 30earthquake.

Table6.LandslideFatalitiesinPariaman(Source:GovernmentofPariaman).

No. District Village Dead

PulauAir 45(25Found,20NotFound)

Cumanak 75(34Found,41NotFound)

1 NagariTandikekatPatamuan

LubukLaweh 132(48Found,84NotFound)

PadangAlai 54(19Found,35NotFound)

2 KotoTimur

KuduGantinginTalao 9(7Found,2NotFound)

SungaiPuaTanjuangMutus 5(3Found,2NotFound)

3 PadangSago

BatangPiaman 1(0Found,1NotFound)

Total 321(58%notfound)

The majority of rural communities living in West Sumatra are situated in agriculturally‐intensive villages near the foot of volcanoes. The reason for locating villages in theseregions isduetothefertilityofthe land.Thecloseproximitytosteepslopesconsistingofweak, weathered pumice makes them particularly susceptible to landslides. ReliefWeb(2009) reported over 1000 landslides triggered by the earthquake. These landslideswereparticularly clustered in the Gunung Tigo highlands between the districts of PadangPariaman andAgamdistricts in the Pariaman region aswell as in Kota Padang and Solokdistricts in thePadang regionas indicated inFigure62.Despite the lowerpopulationandpopulationdensityinthesemountainousregionsascomparedtotheurbancityarea,therewasahighnumberof casualties (about1/3of the total fatalitiesdue to theearthquake).This high number of fatalities could be partly attributed to a large number of villagersattending a wedding ceremony in Cumanak Village (see location in Figure 62), where amajorlandslideoccurred,butmainlyduetotheverylethalnatureofthelandslides.


Figure62.Earthquakeintensityandlandslides.

Manyofthesurvivinglocalresidentslostmostoftheirfamilymembers.Figure63showsthethree landslide sites visited in theworst‐affected district ofNagari Tandikek in Pariaman.Twovillages,PulauAirandCumanakwerevirtuallydestroyedbytheselandslides.

CumanakVillage


Figure63.Relativelocationsandtopographyofthreelandslidesitesvisitedduringthesurvey,superimposedonGoogleEarthwithNUSCRISPSoverlay.

LandslideSite1

The first landslide was accessible via car. The height of the scarp and runoff distancemeasured were 65 m and 230 m respectively The characteristics of the landslide asmeasuredbyaGPSsurveyaregiveninTable7


Table7.CharacteristicsofLandslideSite1.

Characteristics EstimatedValues

Elevationoftopofscarp 247m

Elevationofbaseofscarp 182m

Landslidelength 230m

Landslidewidth(max) 120m

Landslidethickness(average) 5m

Maximumslopeangle 45o

Landslidevolume(assumeellipsoidalshape) 10,210m3

Landslidevelocity 49m/s

Theestimatedlandslidevelocitywas49m/sfollowingSlingerlandandVoight(1979).Asthelandslide resembles thequarterellipsoid‐shapedmasswith itsmaximumwidth coincidingwithitstoe,thelandslidevolumewasapproximatedtobe10,210m3basedontheformulabyCrudenandVarnes(1996). Figure64showsthephotosofthelandslidetakennearthesummitandtherunofftoe.

Figure64.ViewsofLandslideSite1nearthesummit(left)andtherunofftoe(right).

LandslideSite2

The 2nd landslide was once Kapalo Koto, a part of the Pulau Air village which has beenburied by the landslide. The concrete slab foundation and brick and timber debris of the

65m65m


destroyed Kapalo Koto elementary schoolwere the only remains in the site as shown inFigure 65. The soil collected from the surface of the landslide debriswasmainly coarseweatheredpumiceasillustratedinFigure66.Suchlightweightandporousmaterialtypicallyoriginates from volcanic rockswhich underwent rapid cooling and depressurizationwhentheywereviolentlyejectedfromavolcano.Theheightofscarpanddistanceofrunoffwereabout100mand750mrespectively.Theestimatedlandslidevelocitywas88m/sbasedonthe formula by Slingerland andVoight (1979). Table 8 indicates the characteristics of thelandslideasmeasuredbyaGPSsurvey.

Figure65.Slopefailure(left)andthefoundationofadestroyedschool(right)atLandslideSite2.

Figure66.Weatheredpumicecollectedfromthelandslidedebris.

100m100m


Table8.CharacteristicsofLandslideSite2.

Characteristics EstimatedValues

Elevationfrombottomtotopofscarp 100m

Landslidelength 750m

Landslidewidth(max) 180m

Maximumslopeangle 45o

Landslidevelocity 88m/s

LandslideSite3

Thethirdlandslidevisitedwasthelargestsitereportedwiththemostnumberofcausalities.TheEEFITteamtravelledtothesiteatCumanakVillagebyfoot.Figure67showselevatedviewsonasectionofthelandslidesitewherethevillagewassited.

a

c)

d)

b)HighPointSurvey


b c

d e

a)Viewlookingupthevalleywiththehighpointofthesurveyindicatedaswellaslocationsforphotos(c)and(d)

b)Highpointofthesurvey,lookingdownthevalleywiththelocationsforphoto(a)and(e)c)ViewlookingupthevalleyfromthehighpointofthesurveyasindicatedinFigure(a)dViewlookingupthevalleyfromthehighpointofthesurveyasindicatedinFigure(a)e)Viewlookingatlandslideadjacenttothesurveyedlandslide.Phototakenlooking

approximatelyasshowninFigure(b)

Figure67.VariousviewsofCumanakVillagelandslides.

Residents reported that a number of relatively large landslides had occurred since theearthquake.ResidentsindicatedthelocationofoneoftheselandslidesandthisisshowninFigure68.Atthetimeofthesurveythewetseasonwasinprogressandtherehadbeentheusual high rainfalls. Locals reported that there had not been a great deal of rain in theweeksprecedingtheearthquake,althoughtherehadbeenheavyrainthenightbeforeandduringthedayoftheearthquake.Rocksamplestakenfromthesite,werelateridentifiedas

e)a)


pumiceandrangedinsizefromgraveltofistsizerock,withthevastmajoritybeinglessthan10mminsize.

Figure68.Raininducedlandslide.

Thelocalswereactivelyremovingdebrisfromtheirhomesforreuseandrebuilding.Onlyahandfulofsmallhousessurvivedthelandslide.Twohouseswerepositionedjustoutsidethelandslide’spath,while a small timberhouse (shown in Figure69)directly in the landslidepathalsosurvived.Localresidentssaidthatthesoil“flewoverthetop”ofthehouse.Thehousedidnotmoveand its inhabitantsurvived the landslide.The treesbehind thehousemayhaveprotecteditfromthemajorityofthelandslideimpact.Apartfromthepedestriansuspensionbridgeandhandfulofhouses,noothersurvivingstructureswerevisible inthisarea. Local residents said that earthquakes have been particularly frequent in Cumanak,andtheynotedthatthevillagewas locatedbetweentwovolcanoes,Singgalang,anactivevolcanonorthwestofthevillage,andTandikek,adormantvolcanonortheastofthevillage.

Raininducedlandslide

Approximaterouteofsurvey


Figure69.Theextendofthelandslidetakenfromthehighpointofthesurvey(left),andshowingthelocationoneofthefewhouseswhichsurvivedthelandslide(right).

Thesitewasdifficulttoaccessandsearchandrescueeffortsaftertheearthquakemayhavebeen delayed by the narrow, winding roads and steep hills. After the earthquake,government aid andNGOs took approximately four days to arrive at the village.Mattersweremadeworstbythedamagedpedestrianbridgewhichwasthesolepassageleadingtothe site. Figure 70 shows the damaged bridge which was still frequently used by theresidentsaftertheoccurrenceofthelandslide.

Figure70.Damagedpedestrianbridgestillfrequentlyusedbyresidents.

The extend of the landslide was about 2 km long and 1.5 km wide measured from thesatelliteimagesfromGoogleEarthandNUSCRISP.


LiquefactionLiquefactionwasobservedatlocalisedareasinPadang.Thisisattributedtoalluvialdepositscomposingofloosesedimentswithhighsandcontent.Inaddition,Padangisonalowlyingcoastalstripwhereahighgroundwatertableispresent.

The tension cracks on the roadnear the coastline as described in the TransportNetworksectionofthisreportinFigure55suggestthepossibilityofliquefaction.ThisissupportedbythecracksarisingfromlateralspreadingnearthebeachasportrayedinFigure71.

Figure71.Tensioncracksarisingfromlateralspreading.

Landwards into the Padang city core, the Mere Amelie Church suffered effects ofliquefaction as well. Sand boils were observed in the school beside the church (YayasanPrayogaSDAgnesschool)asshowninFigure72.Thiscanbesubstantiatedgiventhatthesesand boils were predominantly silty sand which came from the soil depths beneath thetopsoil. Teaching staffs in Universitas Negeri Padang, a university near the coast andoccupantsofshophousesalsoreportedseeingfluidisedsandseepingthroughtheircrackedfloorslabs in theircompounds.However, thesesandboilswereclearedupsoonafter theearthquaketoresumelessonsandbusinessesrespectively.


Figure72.SandboilsinadjoiningbuildingofMereAmelieChurch.

In low land regions such as the Siteba andPerumdamVillages, clear signs of liquefactionwerealso sighted.Awell inSitebaVillagehadbeenchokedby the rising sanddue to thebuildupofporewaterpressureduringtheearthquake.Inordertocontinueprovidingwaterto the village, the sand in the well was excavated after the earthquake. The well andexcavated soil are as shown in Figure73. Theexcavated soilwas auniformly graded finesand,confirmingliquefaction.

Figure73.Thewell(left)thatwasblockedwithsand(right)duetoliquefaction.

InPerumdamVillage,twoadjacentsinglestoreyhousesneartheriverhavesufferedfromtheeffectsof liquefaction.Excessporewaterpressurehadbuiltupbelowthe floor slabs.ThisledtotheupheavalofthefloorslabsasportrayedinFigure74.Oncethecracksinthefloorslabshadopenedthewatercouldflowoutthusrelievingtheexcessporepressureandallowingthefloorslabstosettlebackdown.


Figure74.Upheavaloffloorslabsduetoliquefaction.


DISASTERMANAGEMENTPostdisasterreliefinIndonesiaisleadbytheNationalDisasterManagementAgency(BNPB)in coordination with the Local Disaster Management Agency (BPBD). This consists ofSATKORLAKPBPatprovincelevelandSATLAKPBPatmunicipality/regencylevel.TheSATLAKPBPisresponsibleforthedisasterfieldcoordinationunitthatissupportedbythegovernorof the region (SATKORLAK PBP). Both of these agencies work under the guidance andsupervisionofNationalDisasterManagementAgency(BNPB),whichreportsdirectlytothepresidentofIndonesia.

The Indonesian government divided the West Sumatra relief operation into 3 phases:emergency, rehabilitation and reconstruction. The emergency response originally wasimplementedfor2monthsfrom1October2009to31November2009.However,sincethelivelihoods in the affected region had already begun to return to normal, the emergencyphasewas implemented foronly1month (except forPariamanandAgamCounty,whichstillneededemergencyrelief).

In general medical services performed very well, with patients from damaged hospitalsbeing transferred to the Dr. M. Djamil General Hospital (main hospital in Padang). Thishospital had the capacity to dealwith allmedical emergencies (see Hospitals Section forfurtherdetails).

Watersupplywasamajorproblemimmediatelyaftertheearthquakeandcontinuedtobeaproblematthetimeofthesurvey;howevercriticalshortagesonlylastedapproximatelytendays.

Rehabilitationandreconstructionactivitiesstartedon1November2009(preparationstage)and it isplanned that the implementationof the rehabilitationand reconstructionphaseswill be performed from 2010 to 2011. The aim of the rehabilitation phase is to returnlivelihoods in the affected area to normal including repair, retrofitting or rebuilding ofdamage infrastructure. The priorities for the rehabilitation phase are housing, publicfacilitiesandinter‐sectoralfacilitiessuchasgovernmentalbuildings.Therehabilitationwillbe followed by a reconstruction phase to improve infrastructure at all levels and toacceleratetheeconomicgrowthintheaffectedregion. IndonesianNationalDevelopmentAgency(BAPPENAS,2009)hassaidthattherehabilitationandreconstructioncostforWestSumatrawillbeapproximatelyRp.6.4trillion(∼USD675million).

As the Indonesiangovernmentquicklyaffirmedaccess to internationalassistance,at least115internationalnon‐governmentalorganizationsjoinedthereliefprocessincollaborationwithgovernment,militaryandnationalvolunteers/organizations.Morethan21searchandrescue teams from 14 countries helped in the evacuation process. Five days after theearthquake (5October 2009), the government and search and rescue (SAR) decided thattherewas littlechanceof survivorsbeing foundand further rescueactivitywouldonlybecarried out by national SAR. International SAR teams were redirected to humanitarian


activity and to support survivors (OCHA, 2009). Itwas also reported that soon after theearthquake, evacuation was mainly focussed in Padang. This resulted in most of theaffectedremoteareasnotreceivinganyaidfordaysbecausetheirsituationhadnotbeenidentified,andseveralaffectedareascouldnotbereachedduetoblockedroadscausedbylandslidesandmajorroaddamage,seeFigure75.

Figure75.BlockedroadinVKotoTimurDistrict,PadangPariamanCounty‐WestSumatra.

Asmanyas288,389buildingsweredamaged inWestSumatraas illustratedbyFigure76.OCHA (2009) identifiedat least 70,000households inneedof temporary shelter.Mostofthepeoplewhohave lost theirhouseshadto live in tents, tarpaulinsandplasticsheetingadjacenttothedamagedhouses. Manyofthesedamagedhousesriskedthepossibilityoffuturecollapse.Toverifythedamagedbuildings,rapidassessmenthadbeencarriedoutbythegovernmentincollaborationwithengineersfromseveraluniversitiesinPadangsuchasAndalasUniversity,BungHattaUniversity,PadangStateUniversityandPadangInstituteofTechnology. Themainobjectiveofthebuildingverificationwastodeterminethedamagelevel of the buildings/houses for the rehabilitation and reconstruction purposes (severe,moderate and light) and also to categorize the safety of house occupancy (immediateoccupancy, life safety and collapse prevention). However, some people ignored therecommendationoftheengineersandstilloccupiedthedamagedhouses,seeFigure77.

Landslideattheupperhillhadblockedtheothersideoftheroad


Figure76.DistributionofDamagedBuildingsinWestSumatraProvince(map:Bakosurtanal,damageddata:BNPBDailyReport19October2009).

PASAMANBARATCOUNTYSevereDamage :3,322ModerateDamage :3,113LightDamage :2,906

PASAMANCOUNTYSevereDamage :180ModerateDamage :38LightDamage :969

AGAMCOUNTYSevereDamage :13,010ModerateDamage :3,838LightDamage :4,460

PARIAMANCITYSevereDamage :8,868ModerateDamage :1,828LightDamage :13,494

PADANGPARIAMANCOUNTYSevereDamage :71,809ModerateDamage :13,530LightDamage :4,741

PADANGCITYSevereDamage :39,535ModerateDamage :39,814LightDamage :41,502

PESISIRSELATANCOUNTYSevereDamage :2,286ModerateDamage :5,555LightDamage :

BUKITTINGGICITYSevereDamage :0ModerateDamage :14LightDamage :61

PADANGPANJANGCITYSevereDamage :47ModerateDamage :232LightDamage :459

TANAHDATARCOUNTYSevereDamage :47ModerateDamage :134LightDamage :117

SOLOKCOUNTYSevereDamage :171ModerateDamage :302LightDamage :432


Figure77.AsmallshopinVKotoTimurdistricthadlostmostofitswallcomponentandimmediatelyopenedafterclearingtherubblecausedbytheearthquake.

AfterbeinghitbytheGreatSumatranEarthquake in2004,awarenessofearthquakesandthe associated hazards such as tsunami and landslide in Indonesia has increasedsignificantly.Thegovernmenthastriedtogiveproperinformationonhowtodealwiththepotential disasters in the prone areas by using leaflets (Figure 78), electronicmedia (TV,radio, etc.) and have also conducted earthquake and tsunami evacuation drills. Disastereducation programmes have also been given to a great number of schools in vulnerableareas in West Sumatra by local NGOs such as KOGAMI – the Tsunami PreparednessCommunity(Dewi,2007).

a). b). c).

Figure78.Sampleofleafletstobuildawarenessforpotentialdisastertothesociety:a).Earthquake;b).Tsunami;c).Landslide(publishedbyBNPB).


Indonesia has developed a tsunami early warning system (Figure 79), but it still needsimprovement to avoid false alarms and to give people reliable information immediatelyafter the earthquake. The time for tsunami arrival is predicted using numerical analysis.There is a system run by (meteorological climatology and geophysical agency) fordeterminingwhethertheearthquakeislikelytobetsunamigenic(personalcommunicationwithUniversityofBungHattaengineers).

When the earthquake occurred, the people in Padang City felt the ground shaking andassumed a tsunami was imminent. This led to wide scale panic and people trying toevacuate to higher ground. There is one major road out of Padang City and to higherground and this, along with minor tsunami evacuation routes, (Figure 80) soon becamejammed with traffic. Meteorology, Climatology and Geophysics Agency of Indonesia(BMKG)madeanannouncedonnationaltelevisionthattheearthquakecausednopotentialtsunami. However, thepeople couldnot receive the informationbecause thepowerhadfailed during the earthquake. The government in Padang tried to reduce panic byannouncingthatnotsunamihadbegeneratedbytheearthquake;Thisannouncementwasmade through loudspeakers attached to cars driving through the main road in the city.Witnessesreportedthatthisdidlittletorelievetheevacuation.


Figure79.IndonesiaTsunamiEarlyWarningSystem(redrawnfromthepictureatBMKGPadangPanjang,2009).


Figure80.TsunamiEvacuationmapforPadangCityproducedbyPT.BinaLingkunganLestari&TsunamiPreparednessCommunity(KOGAMI).


5. CONCLUSIONSANDRECOMMENDATIONS

The conclusions made by the team based on their observations and correspondingrecommendationsare:

Thetimingoftheevent(17:16localtime)wasveryfortuitous.Allschoolswereemptyandmostbusinesseslocatedinmajorstructureshadnoorfewworkerswithin. Thishelpedtoreducethecasualtyfiguressignificantly.

The pattern of observed building collapse was very variable. Many poorer types ofconstructionsurvived,whileseeminglyengineeredstructurescollapsed.Thedistributionofthese failures was also very variable, with structures that had collapsed located next tootherswithlittledamage.Thissuggestseitherveryvariablesoilconditionsorveryvariableconstructionquality–oracombinationofboth.

Theconstructionofschoolshadpoorearthquakeresistanceandasaresult,schoolssufferedverybadly.Itisrecommendedthatriskassessmentsbemadetoallschoolsintheregion.

LargerengineeredbuildingsinPariaman,althoughmuchclosertotheepicentre,seemedtofarebetterthanthoseinPadang.Thiscouldbeduetoeitherthefocusoftheearthquakebeing very deep, the different soil conditions in the two areas or the quality of thesupervisionoftheconstructionbetweenthetworegions.

InPadang,extensivedamagewasobserved inmanyengineeredbuildings. Buildingsovertwostoreysseemedtobethemostaffected.Althoughthesetypesofbuildingswouldhavebeen engineered, they often performedworse than simple, poorly constructed buildings.Again, this could be due to the depth of the earthquake filtering out the high frequencycomponentsandresultinginalongerperiodspectralcontentinthegroundmotionsfurtherfrom the epicenter. This sort of ground motion would be more damaging to the tallerbuildingsinPadangwhilethegroundmotionsnearertheepicentermaynotaffectthetallerbuildingsthere. Anotherreasonforthefailurepatternofthesebuildingscouldbeduetodifferencesinthesupervisionoftheconstruction.

Softstoreycollapsewasbyfarthemajorfailuremodeobservedinengineeredbuildings.Itis recommended that a risk assessment be made of all existing major buildings andimplementationofstrongcolumn/weakbeamdesignphilosophyforallnewbuildings

Industrialandportfacilitiesperformedextremelywellandonlysufferedminormechanicaloroperationaldamage.

Therewereexamplesofbuildings thathad received strongground shaking (evidencedbythe major damage to masonry infill) that had suffered little structural damage. ThissuggeststhatthelatestIndonesianearthquakecode,itsdesignpracticesandconstruction,


is capable of providing the guidelines for designing and constructing buildings that areseismicallysufficientforanearthquakeofthisintensity(structurally,atleast).

Therewasextensivemajordamagetonon‐structuralmasonryinfill.Thisisamajorproblemwith West Sumatran (and possibly Indonesian) construction. It is recommended thatresearchintoalternativedetailsbeconducted

Itislikelythatbuildingsareeithernotbeingdesignedtothecode,orwhatisbeingdesignedis not being constructed (although this may only be true for older buildings). Buildingsupervisionandapprovalproceduresshouldberevised.

The response of lifelines was variable, with the major problems resulting from lack ofelectricityfor10days,damagetothemainwaterline,andlackofmobilephonecoverage.Temporary water tanks, water storage trucks, and transportable, diesel‐generate mobilephonemastswereusedasshort‐termsolutions.ThemainPadanghospital (Dr.M.Djamil)respondedwell and effectively gathered its resources to treat all incoming patients fromsurroundingareas.

Tsunami evacuationplans need to be revisited. Thewarning time for the tsunami is toolongtoeffectivelystoptheevacuationresponseduetonontsunamigenicearthquakes.

Building foundation failures were minimal in Padang which indicates proper foundationdesignforengineeredbuildingsingeneral.Settlementsweremostsignificantnearthecoastwithcontinuouscracksonfloorslabsofbuildingsandflexibleroadpavements.

Evidencesofsoilliquefactionintheformofsandboildepositionandupheavaloffloorslabshavebeenobserved.Awaterwell inaruralvillagewasalsoblockedwithsandduetotheincreaseinporewaterpressure.Lateralspreadingwasseenalongthecoastlineaswell.

Landslidesareamajorthreattothisregion.Thelandslidesvisitedbytheteamcanonlybedescribed as “enormous and lethal.” The greatest concentration of the deaths from thisearthquake was due to landslides and there was very little chance of survival for theresidentsofthehousesinthepathofoneoftheselandslides.Consideringthereislikelytobeanotherevent in thenot‐too‐distant future, there is anurgentneed toassess the riskposed by earthquake induced landslide inWestern Sumatra. The devastating effect thattheselandslideshadonthecommunitiesinPariamanisaverystrongargumenttoperformhazardassessmentinotherregionsoftheworld.


6. REFERENCES

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BAPPENAS (2009). ‘Rencana Aksi Rahabilitasi dan Rekonstruksi Wilayah Pasca BencanaGempa Bumi di Provinsi Sumatera Barat Tahun 2009‐2011’, Kementrian NegaraPerencanaanPembangunanNasional/BadanPerencanaanPembangunanNasional.

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Cruden, D.M. and Varnes, D.J. (1996). Landslide types and processes. In: Landslides:Investigations and Mitigation, Chapter 3. Turner, A.K. and Schuster, R.L. (eds),TransportationResearchBoard,SpecialReport247,pp36‐75.

Dewi, P.R. (2007). ‘School Education Program in Padang City’, US IOTWS TransitionWorkshop,Bangkok.

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the padang, sumatra - indonesia earthquake of 30

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