TheSkopjeearthquakeoccurredfortyyearsagoat5inthemorningon26Julyin1963.Itwasa mediummagnitudeearthquake(M=6.1)ofthekindthatinasparselypopulatedregionmighthave caused much less concern. Unfortunately, it occurred in a densely populated area and it had appalling consequences.Itkilledabout1,200peopleandcausedatotallossof40percentofthevalueofthe built environment of the city. Destruction was very localised which is typical feature of a very shallow shock that happens to occur on an urban centre not designed to resist earthquakes. Whatfollowsisachronologicalaccountoftheeventsfollowingtheearthquaketakenfrommy reporttotheUNResidentRepresentativeinBelgrade,datedOctober1965.Fortheperiodbefore August the Gradsko Sobranje of Skopje provided information; from August onwards information was taken from my own diaries and reports. Friday, 26th July, 1963.The earthquake began at 5 hours 17 minutes and 11 seconds local time, on Friday26thJuly1963.Inabout5secondsitwas all over.The city was left shattered, covered with clouds of dust, and everything was in a state of confusion. Inanumberofplacestransmissionlineswereshort-circuitedandtheautomaticswitchesofthe electricity plants fell, leaving the city without electricity. The telephone lines were also disrupted and thewirelessstationsweretemporarilyputoutofaction.At10oclock,however,contactwiththe outsideworldwasestablishedanddetailsofthedisasterreachedBelgrade.Pre-arrangedemergency plans were automatically put into action throughout the country. Immediately after the earthquake a number of committees took action to coordinate the activities of the various working parties in the city.Drinking of tap water was forbidden until all leaks had been repairedandthearmyundertooktosupplythecitywithover300,000litresofdrinkingwaterdaily.Strayanimalswerebeingroundedup, killed and buried to avoid rabies and other diseases spreading into the city.In the meantime, a small number of fires in the city were extinguished and rescue teams begantheirwork.Organisedteamsofmilitiawithcitizensandminersrescuedwithinthefirstday 325 people from the ruins, and the city was immediately cordoned off and all means of transportation wererequisitioned.Looterswerepunishedonthespot.Afieldhospitalwassetupfromwhatwas leftofthedestroyedhospitalsofthecity.Inthefirst day, over 200 operations were carried out and over1,600casesweretreated.Anair-bridgeestablishedlaterinthedaywithothercitiesin Jugoslaviawasusedtoevacuate180 seriously injured people and medical supplies were flown back intothecity.InBelgrade,thegovernmentappealedtocountriesabroadforhelp,andtheLeague of Red Cross Societies was informed the same day and sent an appeal to all its national organisations. Saturday,27thJuly.Aftershockscontinuedthroughoutthefirsttwodaysandfromtimetotime ruinscollapsed.Throughoutthenightrescueteams,whichnowconsistedofover9,000people, continued a more organised search of the ruins, recovering another 300 bodies.Early in the morning, farmers brought food supplies, mostly vegetables and fruit, into the city from surrounding settlements.Theauthoritieswerenowconcernedwiththeoutbreakofdiseaseandinspiteofthestringent measurestheyhadtaken,theydecidedtoevacuateallunabletobeofhelp.Peoplewerebeing The 1963 Skopje earthquake revisited N. Ambraseys Department of Civil Engineering, Imperial College London SW7 2BU vaccinated with the vaccines salvaged from the ruins.By mid-Saturday the evacuation of women with children began.These were followed by groups of children evacuated mostly to different parts of the country, where they stayed with families or in hostels. TheJugoslavairforceswerenowmobilisedandsuppliesbyairbegantoarriveinthecity.Not morethan36hours after the earthquake, planes with blood plasma, antibiotics, medical instruments, tents and blankets began to arrive from Bulgaria, Czechoslovakia, Denmark, East and West Germany, Italy, Norway, Poland, Sweden and the U.S.A. Anumberofspecialgroupswereorganisingurgentrepairstotheelectricitylinesandthewater supply,andwerealsoparticularlyconcernedwiththeevaluationofthesituationcreatedbythe earthquake. The U.S.A. Army flew in a field hospital with 120 beds and 200 doctors, nurses and orderlies, from Germany.Withtheseconddayaftertheearthquakeatitsend,610bodieshadbeenfound,andover 2,000 cases had been treated at the field hospitals.A special office was set up for the identification of the recovered bodies and for the issuing of death certificates. Sunday, 28th July.The rescue teams continued their search for trapped people in the ruins, assisted byFrenchrescuersequippedwithsound-detectingequipmentcapableofpickingupsoundatsome depth. Theevacuationofchildrenbetweentheagesof7and14continued,andconsiderablenumberof destitutefamiliesbegantomoveoutofSkopjeoncarts,trucks,oronfoot.Someofthemstayedin thesuburbsofSkopje,whichhadsufferedverylittledamage;otherscontinuedfurther,tosettle temporarily in villages or towns allotted to them.These outgoing convoys created traffic jams as they movedthroughin-comingtrafficofarmylorriesandheavybulldozers,andcausedconsiderable delays. Airplanesbeganthesprayingofthecitywithdisinfectants.MoreairplanesfromFranceand PolandcarryingsuppliesarrivedandRedCrosslorriesfromSwitzerlandandEastGermanyarrived with medical supplies and equipment. By the end of the day, parties of engineers had checked the leakage in the water supply system and thiswasrestoredlateonSunday.Othergroupsofengineersbeganthestudyofasystematic demolition programme for the wrecked buildings, which had no historical or cultural value.National treasures,archives,andimportanthistoricaldocumentswererescuedfromtheruins,cleanedand stored in safe places.Fortunately, none of the documents was lost. Monday,29thJuly.ByMonday,over100,000peoplehadbeenledoutofthecity,andthe traffic began to get out of hand. Late on Monday it was decided that the debris should be cleared away and those not already found shouldremainwheretheywereandburiedundertheruins.Thewreckagewassprayedwithstrong disinfectants and removal of the ruins began with explosives and bulldozers. Therewasnourgenthousingproblemsincetheweatherwasverygood,andoverhalfofthe inhabitantshaddeparted.Forthosewhostayed,temporaryshelterintentsandimprovisedbarracks was found for the moment.The public services were set up in the parks, sheltered under light roofs, andbegantofunctionbytheendofthemonth.Theworkwascarriedoutonacontinuousshift systemfor168hoursaweek,andtheworkofassessingthesituationcreatedbytheearthquakewas given first priority. Foreignaidinsuppliesandmoneykeptpouringintothecityandtheauthoritiesweretryingto make the best use of it.Tents, beds, blankets, kitchen utensils, clothing, food, machinery, bulldozers, and medical supplies were all unloaded in Skopje. August 1963.A special committee composed of civil engineers, architects, town planners and land surveyors began to examine all the structures within the epicentral area and to classify them according to damage.All houses were marked with heavy lines of paint showing their structural condition.One redlineindicatedthatthehousewasbeyondeconomicrepair(44.3%).Oneyellowlinemeant structuraldamagetothereinforcedconcreteskeletonofahouse(1.3%);twoyellowlinesindicated structural damage to a brick-wall bearing house (20.8%).One green line designated no damage to the skeleton of a house but some damage to its brick work (0.6%); two green lines meant slight damage to askeletonbuilding(1.4%)andthreegreenlinesindicatedslightdamagetoabrickbuilding(14%).Finally,11.4%ifthetotalnumberofbuildings,irrespectiveofsizecollapsedand6.1%werenot examined, being either slightly damaged or very small. ThisclassificationwasrepeatedinApril1964,usingmorerealisticcriteria,andaconsiderable number of yellow lines turned into green and some red into yellow.However, it is rather difficult to quote exact figures for the percentage of damage to various structures.In greater Skopje, it is safe tosaythatonethirdofthebuildingsweredestroyed,onethirddamaged,butwhichcanberepaired economicallybutnotstrengthened,andonethirdundamaged.Theremainingtenpercentofthe buildings are on the borderlines of the last two categories. Out of the 34,798 dwellings in Skopje, 9,217 survived the earthquake with minor damage, and late in August it was revealed that a better situation existed than had been thought. The Jugoslav Corps of Engineers together with 450 military engineers from the USSR with heavy equipmentcontinuedtoclearupruins.ElementsoftheJugoslavYouthBrigadearrivedinSkopje earlyinAugust.Demolitionworkoflightstructures,salvageofusablematerialsandclearingof rubbleweretheirtasks.Someholdthatintheiryouthfulenthusiasmtheyhinderedasmuchasthey helped. The problem of providing shelter for at least 17,000 families before the winter created an extremely difficult situation. Most of the factories in greater in Skopje were not damaged, and from the factories in the Skopje area only 10% were out of action.Although by the end of the month Skopje received a total of six million pounds in money, materials and equipment from over 40 countries, its deficit was still colossal.For the economy of the republic not to collapse, men had to be asked to return to work, provided they could be housed with their families. EarlyinAugust,missionsofexpertsbegantoarriveinSkopje,sometohelptheauthoritieswith theircurrentproblemsandotherstostudythescientificsideofthedisaster.Atthesametimethe Jugoslav authorities set up a commission for the scientific study of the earthquake and the work was divided amongst the six major Universities of the country.Each University undertook the study of a particular part of the city.The Geological and Seismological Institutes of the country began the study oftheearthquake.TheTownPlanningInstituteofMacedoniaundertookthestudyofthe redevelopmentofthecity.InalltheseactivitiesU.N.andU.N.E.S.C.O.contributedbysending experts to help the planners with their problems. September 1963.The question of building the new city in a safer place arose early in the previous month. This was a complicatedscientific,economic,socialandpoliticalproblem,thesolutionofwhichoccupiedour Yugoslav/UNconsultativeteamforalongtime.Ourfinalrecommendation,whichIpresentedin Belgrade, was that our study revealed that on the basis of the data available, there was no good reason formovingthecitytoasafersite.AllsitesintheVardarvalleyhavethesameprobabilityof occurrenceofstrongearthquakes.Moreover,Skopjewasfarfrombeingtotallydestroyed,andits damage had originally been exaggerated to some extent.Bytheendofthemonth,afterthedecisiontorebuildthecityonitspresentsite,therepairof damagedblockofflatswasunderwayandover30,000workersarrivedinSkopjetorepair10,000 flats for the winter.Prefabricated house units also arrived from the northern parts of the country and from abroad. The clearing up of the city continued. Ruins and buildings of no historical value, damaged beyond repair, were blown up and cleared away, much to the disappointment of those who arrived too late to studytheirengineeringdefects.Buildingsofsmallvalue,hinderingtheredevelopmentofSkopje, were also pulled down. Duringthemonth,moreexpertsarrivedinSkopje,andmoreproblemsarose.Themainproblem now was how and where to accommodate the returning inhabitants of Skopje. A legal authorisation of the State deferred payment of credits granted before the earthquake for people who lost their property, andtheyalsoreceivednewcredits.Anationalloanwithaninterestrateforsavingdepositswas establishedandeverybodywasaskedtocontributewithafairproportionofhisincometofacilitate the economy of Skopje. Thepeoplebegantoreturnhomeslowly.Thepopulationofthecitybegantoincreaseand workersreturnedtotheirjobs.Reconstructionandrepairworkwereintensifiedandthetown-planners and engineers, assisted by UN/UNESCO experts, laid down the plans for new Skopje. It was about the time I gave up my Nissen hut and moved in with a family. October 1963.Early in October the evacuated families started to return in larger numbers; there were now some 150,000 people in Skopje, as more than 80% of the industrial enterprises of the city hadrecommendedtheiractivities.Atthe same time labourers from the surrounding country, mostly unskilled, poured into the city to find jobs in the repair of the damaged buildings.Business flourished againandlifewaseased.Schoolsreopenedandlessonsweregivenintentsorintheopenair.Fortunately the weather was still fine.In the meantime, repair and strengthening work continued to damaged building but without a definitebuildingcontrol.However,notallofthepasterrorsinbuildingmaterialsandmethodsof constructionwere repeated, although in some cases building methods were still, and they will be for some time, far from adequate. By the end of the month the weather changed and heavy rains caused the Vardar River to rise rapidly.Skopje was for a few hours in danger of being flooded again as had happened in 1916, 1935, and1937andshortlybeforetheearthquakein1962.Theheavy rains inundated a number of camps and a few houses, damaged by the earthquake, collapsed. This event proved that there was no point in planninganewtownandprotectingitfromearthquakehazardswithoutplanningsimultaneouslyits protection from floods. Throughout the month the construction of satellite units of prefabricated houses continued withanever-increasingtempo,andmanyhundredsofrepaired,thoughmostdefinitelynot strengthened buildings were handed over for habitation. November1963.Theprojectre-housingschemeforthewinterhadbeencompleted.Small groups of temporary satellite settlements, with water mains, sewer or septic tanks and electricity lines, encircledthecity.Eachsettlementhadaname,asortofashoppingcentreandtransportfacilities. TheUniversityofSkopje,whichwasdamaged,resumednormal tuition late in November. The State undertooktheresponsibilityofschoolarrangementsfortheyoungpeoplewhohadleftSkopjeafter the evacuation and had not returned.For a few years to come the people of Skopje necessarily lived in satellite-settlements of prefabricated houses around the damaged city. Skopje had no definite building code and no regulations for the earthquake resistant design ofstructures.Also,buildingmaterialsandmethodsofconstructionwerefarfromadequate.The Jugoslavauthoritiesbegantostudytheproblemofstandardisingtheirmaterialsbeforethe reconstruction stage.Better bricks, mortar and better workmanship had to be obtained.Also building codesbasedonthelocalconditionswerestudiedandtherehabilitationofthehomelesspeoplein temporaryshelterswasplannedinconjunctionwiththedesignofpermanenthousingsothatthe availablefundscouldbeutilisedtotheirmaximumefficiency.Withinthefirstyear,Skopjebought 13,812prefabricatedunits,ofwhichonly2,549wereimported,therestbeingmanufacturedin Jugoslavia 1964-1965. The main events during the year following the earthquake were:the strengthening of damagedbuildings,thepreparationforanewmasterplanoftheSkopjeregion,urbanplanning, trainingoflocalpersonnelinbuildingtrades,andtheformationofaninternationalboardof consultants. AboardofconsultantswassetupbythegovernmentwiththeassistanceoftheUnited NationsandofitsspecialisedagenciestohelpintheplanningandreconstructionofSkopje.The boardincludedexpertsinurbanandcityplanning(Jugoslavia,USA,Holland,Hungary,Poland) seismology(Czechoslovakia,USSR.),engineeringseismology(USSR,UK),buildingmaterials (USSR.,USA.),sociologyandeconomics(Jugoslavia).Theboardmetforonetotwoweeksevery three months to consider the problems that arise as the plans advance. Engineers,architectsandotherscientistsfromSkopjeweresentabroadfortrainingin modernmethodsofconstructionandintheearthquakeresistantdesignofstructures.Latein1964, and international seminar on earthquake engineering took place in Skopje under auspices of UNESCO and of the Jugoslav government, to review the scientific and applied aspects of the 1963 earthquake. ATrainingandResearchInstituteforSeismologyandEarthquakeEngineering,the forerunnerofIZIIS,wasestablishedbytheUniversityofSkopje,euphemisticallyknownas MissengradorBarakagradwhich,withthehelpofUNESCOstartedtuitionearlyin1965.Jugoslavscientiststrainedabroadandinternationalexperts,togetherwiththestaffoftheUniversity composed the temporary staff of the Institute.

TheideatoestablishaEuropeanAssociationforEarthquakeEngineeringwasconceived38 years ago. In the spring of 1964, following the earthquake in Skopje a year earlier, three members of theUNConsultativeBoardfortheReconstructionoftheCityofSkopje,namelyProf.Sergej Medvedev(USSR),SergejBubnov(Jugoslavia)andNicholasAmbraseys(UK),metinBled,in Slovenia,andsignedanagreement,sponsoredbyUNESCO,fortheestablishmentofaEuropean Commission for Earthquake Engineering.The first symposium of the newly formed commission was held in Skopje on 1 October 1964, and it was followed by a second symposium in September 1969 in Madrid. In the ten years that followed, the Commission, lead by the triumvirate of its founders, known atthattimeastheSvetaTroyka,developedintowhatistodaytheEuropeanAssociationfor Earthquake Engineering. TheEuropeanAssociationforEarthquakeEngineeringtoday,andtheInstituteof EarthquakeEngineeringinSkopjeIZIISowetheirexistencetothesuccessfulwayinwhichSkopje was rebuilt. As a result of the earthquake 40 years ago engineers in Makedonia acquired an expertise in earthquake engineering to the extent that some of them served as UN experts in other parts of the world, and engineering seismology became an invisible export. Makedonia was one of the first in Europe to install a strong motion accelerograph and record an earthquake in Debar in 1967. LessonslearntWhatfollows is a summary my Aide Memoire to the UNDP office in Belgrade latein1967,andoneofmy contractual obligations at the end of my 1967 secondment to UNESCO. TheyearsthatfollowedtheearthquakeSkopjewasagreatschoolforbothlocalandforeign seismologists and engineers who worked together for quite a few years and wanted to learn from it. In the process of planning the new Skopje, a number of important points emerged, brought out from the experience gained in dealing intimately with the problems created by the earthquake. ItwasherethatIrealisedthatasourknowledgeofthecomplexityofearthquakeshas increased,webecomemoreandmoreawareofthelimitationswhichnaturehasimposedinour capacitytopredict,onpurelytheoreticalbases,groundmotions,theperformanceofengineering structures, of the ground itself or of a community. I always felt that the field study of an earthquake offers a unique opportunity to develop an intimate knowledge of the actual situation created by an earthquake and above all an understanding of therealascomparedwiththetheoreticalproblemsthatneedimmediatesolution.Suchan understanding,Ithink,cannotbegainedtodaysimplyfromlectures,readingreportsorby"surfing" the Internet.Spending a long time at a site destroyed by an earthquake allows the interaction of ideas and thetestingoftheoriesinsitubetweencolleaguesofdifferentdisciplines.Itprovidesthelocal authoritiesconcernedwithafirst-hand assessment of the situation created by the disaster, as well as withvaluableandimpartialadviceabouttheimmediateorlong-termmeasurestobetakenforthe restoration of normal conditions in the affected area. The assessment of earthquake risk cannot be achieved by relying only on what one reads in scientificjournals.Riskinvolvesunderstandingalsothevulnerabilityofman-madestructuresof differentkindsandoftheirfoundations.Fieldstudies,therefore,notonlycontributetothe informationavailablebutalso,incombinationwithinstrumentaldataimproveourknowledgeabout thelocalhazardandvulnerabilityofengineeredandnon-engineeredstructures.Itisonlythrough properly-runfieldworkexistingbuildingcodesandbuildingregulations,aswellastheefficacyof their enforcement and implementation, can be tested. It is by an efficient field study that the economic and social repercussions of an earthquake disaster can be identified, thus helping to avoid undesirable effects of future events. TheearthquakeinSkopjeprovedoncemorethatgroundaccelerationsduringstrong earthquakescouldbeveryhigh.By1966theanalysisfromdisplacedobjectsanddeformationsin buildings I had found that the ground motion was a single pulse, of short period and large acceleration withresultinggroundvelocitiesofmorethan0.5m/sec.Baseshearcoefficientsforshortperiod structures(0.2-0.3secs)werefoundtobewellover48%droppingofftoverylowvalues(8%)for structures of longer period (0.8-1.2 secs). It took sometime for these large accelerations to be accepted by the profession in Skopje. Thereweretwootherinterestingpointsthatemergefromthestudyofthedistributionof damage in Skopje.First, the area of the most severe damage correlated surprisingly well with the part ofthecitythatwasfloodedinNovember1962,justninemonthsbeforetheearthquake,andwhere intensive pumping from basements of buildings resulted in producing a weakening of the foundations.As a matter of fact, after the flood, but before the earthquake, minor damage to structures in this area was noticeable mainly due to differential settlement of their foundations.Second, the central part of thecityissituatedonthethinnestlayerofalluvium,whichdipssharplytogreatthicknesseastand west of the city. Undoubtedly, the way in which the rescue, rehabilitation and the reconstruction of Skopje were handled is worthy of praise; particularly since the country was in a stage of rapid but extremely difficult economical development. One may argue that the destruction in Skopje was localised within 10squaremilesonly,andthatthesituationwaseasiertohandle,orthattheforeignaidwas substantial.Thisistrue,butSkopjewasalsothenervecentreofMakedoniaandthiswas,forall practical purposes destroyed. Thereliefofacountrycrippledbyanaturaldisasterislargelybasedontheeffortsofits inhabitants.Inmostoftheeconomicallydevelopingcountriesthemajorityofthepopulationis ignorant about the dangers that natural forces have in store for them, and those who do know have no ideaoftheiraftereffects.Superstitions,misinterpretationsofwell-knownnaturalphenomena,and ignorance often lead to additional disasters. It is not so much what one can prescribe for those affected by an earthquake as what one can achieveintheunderstandingofparticularneedsandthe gaining of the cooperation of the inhabitant thatisimportant.Inaseismiccountry,thepopulationmustbetaughtaboutnaturalphenomenaand their effects, at an early stage of their lives.Courses in earthquake engineering should be included in TechnicalUniversitycurricula.Moreover,modernideasinearthquakeengineeringshouldbe included and current design studies be discussed. Postgraduate research in earthquake engineering in universities is absolutely essential.Apart from attracting those who wish to study the subject further, itgivesanimpetustoundergraduateeducation.Itresultsinproducinganucleusoffutureresearch workersandlecturersonearthquakeengineeringandinadvancingmodernideasaboutthesubject. These argument supported the creation of IZIIS. Inordertominimisethedamagethatmustberepairedafteranearthquake,someformof Code or Regulations for building in earthquake regions should exist, and also means of enforcing such aCode.Thiswillrequiresomeorganisationbeforeanearthquakeoccurs.Experiencetobegained fromhalf-measurestakenbyvariousgovernmentstominimisedamage,thoughvaluable,willbeof little use if applied without proper understanding of the local conditions by another government or in anothercountry.Simplerules,nomatterhowwelltheymayapplyinonepartoftheworld,may provecompletelyinsufficientorevendetrimentalinanother.Suchrulesshouldbeintendedasa startingpoint,theyshouldbestudied,andamendedasneedbeineachcountrybyacommitteeof professional men who are familiar with the problems involved.There is no way of producing rules-of-thumb which will be generally applicable, or effective, without adapting them to local conditions.Thispresupposesthateachlocalauthorityshouldputsomeeffortintoadjustingtherulestofitits particularrequirements.Toprovidestandardisedrulesforcountries,whichwillnotundertaketo adjustthemtotheirlocalconditions,isahalf-measure,whichcaninnowayreplacetheresultsifa determined interest by the various local authorities.

Thisworkhasgrownoveraperiodofalmostonedecade,andhasowedmuchtothe contributionof individual personalities at various stages. It would be impossible to mention here the namesofallthepeopleandinstitutionsthathavehelped.MichaelFournierdAlbeof UNESCO has done so much that he must be mentioned before any other. Milan Arsovski, Dragan Hadzijevski, Kole Jordanovski,TiberiasKirijas,TrifunPaskalov,JakinPetrovski,ApostolPoceski,BlagojePopov, Patska Sokolovska (my minder) and Velkov were among those whose help is greatly appreciated.