ComparingthecurrentimpactoftheVanEarthquaketopastearthquakesinEasternTurkey
CEDIMForensicEarthquakeAnalysisGroupReport#4Status:WednesdayNovember2nd,2011,18:00CentralEuropeanTime
(Builtwithsupportofearthquakereport.com,SOSEarthquakes)
TABLEOFCONTENTS
1. IntroductionandSetting 1
2. TheImpactofthe2011VanEarthquake(Seismology,SocioeconomicLosses,AidandShelter) 3
3. ComparisonsoftheVanEarthquakewithrecenthistoricEastTurkishEarthquakes 18
4. SocialVulnerability,ReconstructionandLongtermimpactsforlivelihoodIssues 21
5. Conclusion 24
UpdateContributors
ProducingthisreporthavebeenJamesDaniell,BijanKhazai,TinaKunzPlapp,FriedemannWenzel,BernhardMuehr,MichaelMarkus (CEDIM,KIT) andArmandVervaeck (earthquakereport.com).WethankMustafaErdik(KOERI)forhisinsightandfruitfuldiscussions.WealsothanktheGeneralSirJohnMonashFoundation,Australia.
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1 IntroductionandSetting
TheVanearthquakein2011hitat10:41GMT(13:41Local)onSunday,October23rd,2011.ItwasaMw7.27.3event locatedatadepthofaround10kmwith theepicentre locateddirectlybetweenErcis(pop.75,000)andVan(pop.370,000).TheprovinceofVanhasaround1.035millionatthelastcensus.TheVanprovinceisoneofthepoorestinTurkeyandhasmuchinequalitybetweentheruraland urban centers with an average HDI (Human Development Index) around that of Bhutan orCongo.Theearthquakeisestimatedtohavecausedaround7001000casualties(601currentlyasof2ndNovember2011;mostlyduetofallingdebrisandhousecollapse),andaround1billionTRYto4billionTRY(approx.555millionUSD2.2billionUSD)intotaleconomiclosses.Thiswouldrepresentaround17to66%oftheprovincialGDPofVan.
From the CATDAT Damaging Earthquakes Database, major earthquakes such as this one haveoccurred intheyear1111causingmajordamageandhavingamagnitudearound6.57.Intheyear1646or1648,Vanwasagain struckbyaM6.7quakekillingaround2000people. In1881,aM6.3earthquakenearVan killed 95people.Again, in 1941, aM5.9 earthquake affected Ercis andVankilling between 190 and 430 people. 19451946 as well as 1972 brought again damaging andcasualtybearingearthquakestotheVanprovince.In1976,theVanMuradiyeearthquakestrucktheborderregionwithaM7,killingaround3840peopleandcausingaround51,000peopletobecomehomeless.
TheHDI(HumanDevelopmentIndex)intheaffectedregion(Van,Hakkari,Bitlis,Mus)isamongthelowest inTurkey.Pleasenote that this is the2009definitionofHDIandnot thecurrentUNDP2ndversion.HDI isacombinationof literacyrate, lifeexpectancyandGDP(percapita). IntheVanarea(0.630),theHDI isequivalenttoBhutan,IndiaorCongo,ascomparedtotheaverageHDIofTurkeywhichis0.810,equivalenttoBrazil,PeruorColombia.Thisreflectstheruralcharacteroftheregion,the fact thatcivilconflictprevailed fordecades,andpoints to reduced localcapacities fordisasterpreparednessincludinghospitalandothermedicalresources.
Figure1:HumanDevelopmentIndexofProvincesinTurkey,showingonemeasureofcopingcapacity
VanProvincehasanofficialpopulationof1.035million (asof31.12.2010,ABPRS)withavery lowpopulationdensitycorrespondingto54.3/km2.Comparedtootherprovinces,theaveragehousehold
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sizeisrelativehigh(between7and8persons).Ithas539,619residentslivingincities,andavillagepopulationof495,799.
The official population of Van City was 367,000 in 2010 as per the Address Based PopulationRegistrationSystem(ABPRS),butvaluesof500,000and600,000havebeenestimatedbygovernmentsources.TheErcispartoftheprovincehasErcisCity(approx.77,000)andmanyothersettlements.(Urban=78,397, Rural=66,832). Based on the available Census data 1985, 1990, and 2000 thepopulationofVanprovince increased substantiallyduring from1985 to2000,both cities at leastdoubledtheirnumberofinhabitantsduringthelast25years.
Table1:PopulationchangesfromcensusinformationforthecitiesofVanandErcisfrom19852010(DataSource:StateInstituteofStatistics,Turkey)
City
1985Census
1990Census
2000Census
20091231Registered
20101231Registered
Van 110,653 155,623 284,464 360,810 367,419
Erci 36,582 40,481 70,881 74,858 77,065
SeethesocialvulnerabilitysectionbelowforafurtherinsightintothedynamicsoftheVanprovinceintermsofreconstructionissues.
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2 TheImpactofthe2011VanEarthquake
2.1 GroundMotionandSeismologyThe Van earthquake in 2011 hit at 10:41 GMT (13:41 Local) on Sunday, October 23rd, 2011.Estimates of the hypocenter range fromMw7.1 toMw7.3 and from 5 to 20km from differentagencies. This corresponds to a seismicmoment release difference of 2 times. The earthquakereleased itsenergyby thrustmotiononanEW trending fault.Faultsofanearthquakeof this sizeextend typically for60 to100km length.Although theepicenter is located in theNorthAnatolianFault Seismotectonic Zone, the faultmotion suggests that the event belongs to the broadBitlisZagrosFaultZone,wherethrustmechanismsdominate.
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Figure2:HypocentersasdeterminedfromvariousagenciesascomparedtothelargepopulationareasofVanandErcis(basepicturecourtesyofKOERI)
Groundmotion estimates have been published by KandilliObservatory and Earthquake ResearchInstitute (KOERI, http://www.koeri.boun.edu.tr/) aswell as Earthquake Engineering and ResearchCenterMiddleEastTechnicalUniversity(EERCMETU,www.eerc.metu.edu.tr).KOERIshowsthattheseismichazardbefore the event,mimicked the locationof the earthquake to cause large groundmotions.Intheepicentralareatheyreachvaluesof60%ofgravitationalacceleration(0.6g)andpeakground velocities of 5060 cm/s. This would be beyond standard code levels. The different
EMSCMw7.3,10km
GeoAzurMw7.2,1623km
USGS2Mw7.3,16km
GCMTMw7.1,15.4km
http://www.koeri.boun.edu.tr/http://www.eerc.metu.edu.tr/
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BoththeVanandErciscitiesarebuiltontheshoresonVanlakewhichsuggestssoftsoilconditions
EMS intensities are estimated as above VIII within an area with 25 km diameter as per KOERI.
Muradiye(No.6503,hypocentraldistance49.1km)PGA=179cm/s
Malazgirt(No.4902hypocentraldistance94.5km)PGA=56cm/s
BitlisMerkez(No.1302hypocentraldistance112.8km)PGA=102cm/s2
AgriMerkez(No.0401hypocentraldistance122.8km)PGA=18.3cm/s
TherelativelyhighvalueatBitlis,wherealsomuchdamagehasbeenreportedmaybecausedbythe
KOERIshowsestimatesofPGAvaluesmodelledwithELER, includingsoileffects,butusingapoint
ThegroundmotionatMuradiyeandBitliswasbelow theTurkishDesignSpectraeven forsoftsoil
hypocenters from various agencies are shown on the following diagram. The KOERI hypocenterappearstocorrelatebesttothedamageseen.
forthecities,possiblysoil liquefactionalongtheshoreofthe lakecausinggreatergroundmotionsandthisaggravatingfactorsforbuildingcollapseandgroundfailure.
However,thesevaluesarecomputed,notmeasuredandmuststillbevalidatedbyfieldobservationsof theTurkish strongmotionnetworks. Strongmotionmeasurementsandmacroseismic intensityobservationsof theepicentralareaarestillnotavailable.TheStrongMotionDataBaseofTurkey:(http://kyh.deprem.gov.tr/ftpt.htm)providesdatafrom22stationsmostofthemat largedistancesbeyond100km.ThestrongmotiondataisinitiallyreportedbyEERCMETU.Thecloseststationsare:
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2
2
EWextensionoftherupturedfault.
sourceinsteadofanEWelongatedrupture.EpicentralPGAsareestimatedas550cm/s2;thisshouldbeessentiallythevalueforVanandErcis.TheKOERImodeliscompatiblewithrecordsoftheStrongMotionDataBaseofTurkeybetween50kmand120km.
conditions(KOERIreport31.10.2011). IntheepicentralareabetweenVanandErcisPGAvaluesareestimatedas550cm/s2, three timeshigher thanatMuradiye.Theusedgroundmotionpredictionequationincludesa35%chancethatthevaluesexceed750cm/s2.Itisthusconceivablethatgroundmotion,atleastlocally,exceededcodelevel.
http://kyh.deprem.gov.tr/ftpt.htm
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Figure3:CourtesyofKOERI(http://www.koeri.boun.edu.tr/)Intensities(EMS)(Left);PGA(%g)(Right)
For those interested in readingabout thedynamicsof theactive tectonic featuresof theEasternMediterranean region and the Eastern Anatolia fault systems at play, we recommend readingSeismotectonicsof theVanRegion andother seismichazarddata createdbyKOERI atBogaziciUniversity.Linkprovidedattheend.
AftershockSequenceAsof31stOctober2011,theaffectedarea isstillhitwithcontinuousaftershocks.Therehavebeenover1792aftershocksgreaterthanmagnitude2.Over7ofthesehavebeengreaterthanmagnitude5, includingaM5.6andM5.9soonafter thequake,aM6.0,10hoursafter theearthquake,andaM5.7whichcausedmuchadditionaldamageincludingcollapsedhouses.Thissequenceofeventshaskeptpeopleonthestreetswithreportsofmanymorepeople leavingtheirhomes.Ascanbeseenbelow, felt aftershocks have been distributed over a large area,meaning thatmost of the VanProvincepopulationhasbeensignificantlyaffected.
Inmany historical earthquakes, aftershocks are themain reason for people staying out of theirhomes, combined with the fear of buildings collapsing until proper assessment is done. In thisearthquake,likethe2011Japaneseearthquake,theaftershocksequencehasproducedalargerthannormalnumberofpeople to leave theirhomeswhodonothave severelydamagedordestroyedhousing.Peoplearestayingoutsideoftheirhomeswarmingupintheheatofacampfireandcoveredwithsheets.
Th
