(Italy) Earthquake of 24 November 2004: A Field Report

EUROPEAN COMMISSIONJOINT RESEARCH CENTREInstitute for the Protection and Security of the CitizenEuropean Laboratory for Structural Assessment (ELSA)I-21020 Ispra (VA), ItalyThe Garda Area (Italy) Earthquake of 24 November 2004:A Field ReportS. Dimova, E. Mola, P. Negro, A.V. PintoA. Colombo (University of Trento)GAVARDO STATION GROUND ACCELERATION RECORD: W-ECOMPONENT403020Acceleration [cm/s2]1000 2 4 6 8 10 12-10-20-30-4014-50Time [s]2004 EUR 21513 EN

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportCONTENTSContents................................................................................................................................ iList of figures .....................................................................................................................iiiList of tables ....................................................................................................................... ivAknowledgements ............................................................................................................... vAbstract..............................................................................................................................vii1 Introduction ................................................................................................................. 12 Seismology and geological aspects ............................................................................. 32.1 Geology and tectonics ......................................................................................... 32.2 Historic seismicity ............................................................................................... 42.3 Description of the earthquake of 24 November 2004.......................................... 52.4 Strong motion records ......................................................................................... 92.5 References.......................................................................................................... 123 Damage distribution: observed microseismic intensity............................................. 133.1 Vulnerability class according to the European Macroseismic Scale................ 133.2 Vobarno ............................................................................................................. 133.3 Collio (fraction of Vobarno).............................................................................. 143.4 Pompegnino (fraction of Vobarno) ................................................................... 153.5 Pavone (fraction of Sàbbio Chiese)................................................................... 163.6 Clibbio (fraction of Sàbbio Chiese)................................................................... 173.7 References.......................................................................................................... 194 Performance of building structures ........................................................................... 214.1 Non-engineered masonry houses....................................................................... 214.2 Engineered structures........................................................................................ 254.2.1 Masonry structures with reinforced concrete slabs ................................... 254.2.2 Reinforced concrete structures .................................................................. 254.3 Conclusion......................................................................................................... 275 Socio-economic effects and management of the disaster.......................................... 29i

The Garda Lake (Italy) earthquake of 24 November 2004: A field report5.1 General ..............................................................................................................295.2 Statistics .............................................................................................................305.2.1 Emergency operations................................................................................305.2.2 Damage and economic losses ....................................................................315.3 References..........................................................................................................336 Conclusions................................................................................................................35ANNEX A..........................................................................................................................37ANNEX B……………………………………………………………………………… 41ii

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportLIST OF FIGURESFigure 2.1. Map of events with M ≤ 4 for the Mediterranean area .......................................Figure 2.2. Map of the events with M>4 for the Mediterranean area ...................................Figure 2.3. Historical earthquakes, 2002 events and tectonic configuration of the area.......Figure 2.4. Epicentre of the earthquake FigureFigure 2.5. Map of the epicentral area (from the C.O.M. in Salò) ........................................Figure 2.6 Seismic Classification Map for Lombardia (from [6]) ........................................Figure 2.7 Moment tensor solution for the main shock.........................................................Figure 2.8. Tectonics of the Lake Garda area........................................................................Figure 2.9. Historical earthquakes, 2002 events and tectonic configuration of the area.......Figure 2.10. Location of the accelerometric stations in the epicentral area (from [8]) .........Figure 2.11. The Gavardo station records of the main shock (NS, WE and verticalcomponents) ..................................................................................................................Figure 2.12. Elastic spectrum for the Gavardo station record of the main shock .................Figure 2.13. Inelastic spectra for the main component (N-S) of the Gavardo station recordof the main shock...........................................................................................................Figure 3.1. A church in Vobarno...........................................................................................Figure 3.2. Slight non-structural damage ..............................................................................Figure 3.3. Damage of a concrete flower pot in Vobarno .....................................................Figure 3.4. Fall of loose bricks in Collio...............................................................................Figure 3.5. Cracks in the masonry walls ...............................................................................Figure 3.6. Failure of masonry wall ......................................................................................Figure 3.7. Separation joint in RC building ..........................................................................Figure 3.8. Collapsed masonry wall ......................................................................................Figure 3.9. Deplanation and cracking of a masonry wall......................................................Figure 3.10. Lack of separation joint.....................................................................................Figure 3.11. Failure of the masonry under the roof...............................................................Figure 3.12. Failure of masonry with poor quality................................................................Figure 3.13. Shear failure of masonry column ......................................................................Figure 3.14. Failure of untied slender masonry wall.............................................................Figure 3.15. Failure of the masonry under the roof...............................................................Figure 3.16. Pounding of adjacent buildings.........................................................................Figure 3.17. Fallen ‘coppi’ tiles.............................................................................................Figure 3.18. Damages of the church......................................................................................Figure 3.19. Partial separation of the façade walls................................................................Figure 3.20. Rock-fall near Clibbio.......................................................................................Figure 4.1. House in Clibbio with a large opening in the bearing wall.................................Figure 4.2. Separation of infills in Collio..............................................................................Figure 4.3. Failure of the unconfined masonry under the roof in Pompegnino ....................Figure 4.4. Failure of the masonry support and of the roof in Clibbio..................................Figure 4.5. Separation of masonry walls in Pavone ..............................................................Figure 4.6. Irregular structure in Clibbio...............................................................................Figure 4.7. Failure of masonry in Pavone .............................................................................Figure 4.8. Sliding of ‘coppi’ tiles in Pompegnino ...............................................................Figure 4.9. Renovated house in Pavone ................................................................................Figure 4.10. Renovated house in Pavone ..............................................................................Figure 4.11. The bell-tower in Clibbio..................................................................................Figure 4.12.The bell-tower in Pompegnino...........................................................................iii

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportFigure 4.13. The church in Clibbio........................................................................................Figure 4.14. The church in Pompegnino................................................................................Figure 4.15. Cracks in the vault of the church in Clibbio......................................................Figure 4.16. The church in Pavone ........................................................................................Figure 4.17. Irregular structure in Pavone .............................................................................Figure 4.18. Pounding of adjacent buildings in Collio ..........................................................Figure 4.19. Failed thin masonry wall in Collio ....................................................................Figure 4.20. Cracked masonry wall in Pompegnino..............................................................Figure 4.21. Hollow bricks used in Pompegnino...................................................................Figure 4.22. Irregular building in Collio................................................................................Figure 4.23. Separation of masonry walls .............................................................................Figure 4.24. Pounding of adjacent structures in Pompegnino ...............................................Figure 5.1. The Salò C.O.M...................................................................................................Figure 5.2. Map of the requested and performed structural safety assessment interventionsat the Salò C.O.M...........................................................................................................Figure 5.3. The Pompegnino C.O.A. .....................................................................................Figure 5.4. The Pompegnino camp kitchen and canteen .......................................................Figure 5.5. Safety intervention on a stone masonry wall.......................................................Figure 5.6. Vigili del Fuoco intervening on the roof of a damaged building inPompegnino ...................................................................................................................Figure 5.7. Safety intervention on a masonry house in Pompegnino ....................................Figure 5.8. Vigili del Fuoco working on the roof of the heavily damage church in ClibbioFigure 5.9. Intervention on the severely damaged Primary School of Pompegnino .............Figure 5.10. Safety intervention in Pavone............................................................................LIST OF TABLESTable 2.1. Minor aftershocks (from the INGV website)........................................................Table 2.2. Recorded data from RAN and temporary accelerometric stations (from [6]) ......Table 5.1. Assisted population in the most damaged villages ...............................................iv

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportABSTRACTOn November 24 2004 an earthquake hit the area of Garda Lake, part of the Lombardiaregion in Italy. The magnitude of the event was estimated in 5.2 on the Richter scale and,at a local level, its effects were remarkable, especially in some municipalities where anintensity of VII-VIII on the MCS scale was reached.The importance of the event, the vicinity of the area, the need to investigate theperformance of buildings and structures to the earthquake called for a field mission by theELSA Earthquake Engineering Staff. The mission consisted of a full-day trip to the area,on December 1 2004, one week after the event, when the effects of the earthquake and itsconsequences on the environment and the people were still evident.This report presents the evidence collected in the trip by means of a completephotographic documentation. Moreover, an introduction regarding the historicalseismicity of the region and an estimation of the main features of the earthquake isprovided. Finally, the behaviour of different categories of buildings, from masonry onesto reinforced concrete, to historical ones, is analysed and discussed and an overview ofthe procedures used to deal with the emergency is carried out.vii

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportviii

The Garda Lake (Italy) earthquake of 24 November 2004: A field report1 INTRODUCTIONOn November 24 2004 an earthquake hit the area of the Brescia province around LakeGarda in Lombardia, Italy. Though the magnitude of the event was 5.2 on the Richterscale, the effects it caused on some of the building stock of the area were remarkable,given the many historical private and public buildings present in the area and the verylarge majority of stone and brick masonry structures in the private housing building stock.The relevance of the event, the vicinity of the area and the need to investigate theperformance of buildings and structures to the earthquake called for a field mission by theELSA Laboratory Earthquake Engineering Staff. The mission consisted of one full-daytrip around the epicentral area and took place on December 1 2004, one week after theevent, when the effects of the earthquake and its consequences on the environment andthe people were still evident.The aim of the present field report is to carry out a thorough overview of the mostsignificant aspects of the event, referring to the evidence collected during the field trip, tothe documentation collected in preparation for the mission and to the informationgathered through exchanges with experts and locals met on the field.In Chapter 2 the seismological framework of the event is traced, referring to the historicalseismicity of the area and to its tectonic configuration; a description of the event is thencarried out. In Chapter 3 a description of the damage distribution, with the observedmicroseismic intensities, is given. In Chapter 4, a detailed description of the damagereported by the different categories of structures present in the area is performed;masonry buildings, reinforced concrete buildings, historical churches are considered; aphotographic documentation gives a vivid representation of the effects of the earthquake.Chapter 5 is devoted to the procedures for dealing with the emergency situation caused bythe earthquakes, in particular data on the homeless, the inspected structures and the otherrelevant statistics that could be collected at the time of the visit. Finally, in Chapter 6, theconclusions drawn from the field trip and the survey performed about the event arepresented.1

The Garda Lake (Italy) earthquake of 24 November 2004: A field report2

The Garda Lake (Italy) earthquake of 24 November 2004: A field report2 SEISMOLOGY AND GEOLOGICAL ASPECTS2.1 Geology and tectonicsThe Mediterranean basin area has a quite complex tectonic configuration. In thisrelatively small area, in fact, different kinds of seismogenetic zones can be found. Someof them are characterized by compressive tectonic movements leading to subduction (theAlps or the Hellenic Arch), some others are characterized by elongation and sliding ([1],[2]).The seismic activity in the Italian Peninsula is mainly caused by the convergingmovements of the African and the Eurasiatic plates. This causes high seismicity in Italy,both from the frequency and from the intensity point of view. The events taking place inItaly are possibly correlated with those happening on the Eastern coasts of the AdriaticSea.The Apennine area shows a mostly diverging tectonic activity, with some areascharacterized by compressive stresses, on the eastern side. This shows a complex activitythat is possibly due to the rotation of the Atlantic micro-plate, added to markeddisomogeneity at crustal level. For this reason, the seismicity in Italy is quite high, as canbe observed in Figure 2.1, where a map of the events with M ≤ 4 in the Mediterraneanarea is represented. In Italy such events are present everywhere.Figure 2.1. Map of events with M ≤ 4 for the Mediterranean areaFrom Figure 2.2, showing a map of events with M > 4, it can be seen that also strongerearthquakes are quite common, especially in certain areas (in the map the squaresrepresent events with 5 ≤ M ≤ 6 and the circles represent events with M 5, reaching 6 for the Irpinia earthquake of1980.3

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportFigure 2.2. Map of the events with M>4 for the Mediterranean area2.2 Historic seismicityThe historic seismicity of the area of Garda Lake is well known. The most relevant eventthat took place in the area was the earthquake of 30 October 1901. On that day a verystrong earthquake hit a number of municipalities in the province of Brescia, part of theLombardia region in Italy.Figure 2.3. Map from the “Parametric Catalogue of Italian Earthquakes”, from [3]In Salò, a small town on the Garda Lake, and one of the areas damaged by the recentearthquake, the intensity of that event reached VIII on the Mercalli Scale. On thatoccasion, diffused cracking to the housing building stock was observed, together with a4

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportnumber of failures; landslides and movements were also reported. In Fig. 2.3 therepresentation of that earthquake in the Italian Catalogue of Seismic Events is reported(from [3]). In [4], the peculiarity of the seismic area of Lake Garda is described as beingthe conjunction ring between the Lombardia and Veneto areas, delimited on one side bythe river Adige and on the other by the river Chiese. A description of the historicseismicity of the area is also given: municipalities such as Salò, Malcesine and Cassoneare reported to have suffered many a strong and localized earthquakes. Among the mostrelevant events, the earthquake of 5 January 1892 is cited: it was reportedly most intensein Salò and Vobarno, two of the municipalities that were also involved in the latest event.The region being delimited by two seismic epicentral areas located on the two oppositesides of the Garda Lake, it has historically resented of the activity of both: when, on theVeneto side (in the province of Verona), periods of intense seismicity came along, on theopposite side (in the province of Brescia) events were often registered at the same timestoo.2.3 Description of the earthquake of 24 November 2004On 24 November 2004, at 23:59 local time (22:59 GMT), a seismic event of magnitude5.2 on the Ricther scale hit the area of the province of Brescia (Lombardia, Italy) aroundLake Garda. The main event was followed by a series of minor quakes, of very smallmagnitude, ranging between 1.7 and 2.1, not felt by the population but recorded by theItalian accelerogram net and reported on the National Institute of Geophisics andVulcanology (INGV) website [5].TIME DATE MAGNITUDE00:48 25/11/2004 Magnitude: 1.700:49 25/11/2004 Magnitude: less than 1.700:53 25/11/2004 Magnitude: 1.700:55 25/11/2004 Magnitude: 1.702:25 25/11/2004 Magnitude: 2.105:22 25/11/2004 Magnitude: 2.0Table 2.1. Minor aftershocks (from the INGV website, [5])The location of the epicentre of the main event can be observed in Fig. 2.4. Acording tothe preliminary report by INGV, the main municipalities located at less than 3 km fromthe epicentre are: Vobarno and Gardone Riviera; in a 6 km radius area from the epicentreare the towns of Salò, Sabbio Chiese and Toscolano Maderno. In Fig. 2.5, a more detailedmap of the area is represented; the relative positions of the small villages of Vobarno,Gardone Riviera and Toscolano Maderno can be observed. This map was located in theC.O.M. (Centro Operativo Misto) of Salò, the emergency management unit set upimmediately after the event and still operative at the time of the field mission (for furtherinformation and a more detailed description of the emergency management proceduressee Chapter 5).According to the new Seismic Classification of Italy, referred to the Nuova OrdinanzaPCM of 20 March 2003 [6], the epicentral area is in seismic category 2: as can be seen inthe map represented in Fig. 2.6, from [7], this means that the horizontal groundacceleration value with a probability of exceedance of 10% in ten years is in the range0.15-0.25g. For the same category, the 0-period horizontal acceleration given is 0.25g.5

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportThe estimated depth of the event was of about 8 km: due to the superficial location of theepicentre, the earthquake was felt over a very large area of Italy, from region Lombardiato Veneto, Piemonte (located in North-East and North-West Italy, respectively), toToscana and Emilia-Romagna (located in the centre of the Italian peninsula), toSwitzerland, Austria and Slovenia.Preliminary moment-tensor solutions for this earthquake carried out by the United StatesGeological Survey, [8], imply that the shock occurred as the result of movement on aninverted fault, as represented in Fig. 2.7. In the picture, the ‘beach ball’ representation ofthe source mechanism for the earthquake is given, together with the slip, dip and strikedata that locate and describe it exactly. This solution was performed by INGV-HarvardEuropean-Mediterranean Regional Centroid-Moment Tensors Project.The tectonics of the area is represented in Fig. 2.8: the main active tectonic structures arereported, together with the epicentres of some historic earthquakes. The event under studywas part of the activity of the Giudicarie fault system.Figure 2.4. Epicentre of the earthquakeIn Fig. 2.9, the epicentre of the 24 November earthquake and its focal mechanism arecompared to the cinematic sources of the seismogenetic system which caused the 1901earthquake (the source is the new version, yet to be published, of the Database ofpotential Sources for Earthquakes larger than M 5.5 in Italy, 2001). It can be seen thatthe recent earthquake is well framed in the activity of the Giudicarie System: both thetype of mechanism (inverted fault) and its direction (strike) are in good agreement withthis conclusion.6

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportFigure 2.5. Map of the epicentral area (from the C.O.M. in Salò)Fig. 2.6 Seismic Classification Map for Lombardia (from [7])7

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportFigure 2.7 Moment tensor solution for the main shockFigure 2.8. Tectonics of the Lake Garda area8

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportFigure 2.9. Historical earthquakes, 2002 events and tectonic configuration of the area2.4 Strong motion recordsAs reported in [9], following the main event of 24 November the Italian RAN Network(National Accelerometric Network) station of Gavardo, located at less than 10 km fromthe epicentre, was activated.Fig. 2.10. Location of the accelerometric stations in the epicentral area (from [9])9

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportThe recorded peak ground acceleration (PGA) was around 0.077g (about 76 cm/s 2 ) on thelongitudinal component (NS direction). Gavardo is an analogic measurement station; nodigital stations are located near the epicentral area. In the following the digitalized signalsobtained from the analogic measurements are reported. The only digital station thatrecorded a signal is located in the Gran Sasso area, in the Abruzzo region, at more than500 km from the epicentre. In the latter station the recorded PGA was of 0.023 cm/s 2 .Starting from the afternoon of 25 November, three temporary digital stations were set upin the area: one of them was located at the Salò C.O.M. (Centro Operativo Misto,described in detail in Chapter 5); the other two stations were located in ToscolanoMaderno, one of them on rock soil, the other on soft soil to point out any possible siteeffects. Of the three aftershocks with magnitude ≥ 2.5 reported by INGV, two were alsorecorded by the temporary digital stations.In Fig. 2.10 the map with the location of the temporary station is represented. Tab. 2.2gives the PGA values and the magnitudes of the main event, as registered in the two RANstations of Gavardo and Gran Sasso stations.Tab. 2.2. Recorded data from RAN and temporary accelerometric stations (from [9])Station A/D Place Time Direct. PGA(cm/s 2 ) MagnitudeGVD A Gavardo 24/11/04 Long. 158.76 5.2(Gazzino) 22:59GVD A Gavardo 24/11/04 Vert. 91.14 5.2(Gazzino) 22:59GVD A Gavardo 24/11/04 Trasv. 99.96 5.2(Gazzino) 22:59GSG D Gran 24/11/04 XTE -0.021 5.2Sasso 22:59GSG D Gran 24/11/04 YLN. 0.023 5.2Sasso 22:59GSG D Gran 24/11/04 ZUP -0.022 5.2Sasso 22:59SAS D Salò 26/11/04 XTE 1.618 2.7(SAL)C.O.M. 05:39SAS D Salò 26/11/04 YLN. 1.943 2.7(SAL)C.O.M. 05:39SAS D Salò 26/11/04 ZUP -6.277 2.7(SAL)C.O.M. 05:39GAI D Gaino 27/11/04 XTE 2.751 2.5(bunker) 08:45GAI D Gaino 27/11/04 YLN. -2.507 2.5(bunker) 08:45GAI D Gaino(bunker)27/11/0408:45ZUP 2.018 2.5In Fig. 2.11 the digitalized ground acceleration recorded by the analogic instrumentationin the Gavardo station (provided courtesy of the Protezione Civile) is reported. The twohorizontal and the vertical component are represented.10

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportGAVARDO STATION GROUND ACCELERATION RECORD: N-SCOMPONENTGAVARDO STATION GROUND ACCELERATION RECORD: W-ECOMPONENT804060304020Acceleration [cm/s2]2000 2 4 6 8 10 12 14-20-40Acceleration [cm/s2]1000 2 4 6 8 10 12 14-10-20-30-60-40-80-50Time [s]Time [s]GAVARDO STATION GROUND ACCELERATION RECORD: D-UCOMPONENT403020Acceleration [cm/s2]1000 2 4 6 8 10 12-10-20-30-4014-50Time [s]Fig.2.11 The Gavardo station records of the main shock (NS, WE and verticalcomponents)In Fig. 2.12, the elastic spectrum computed for the main shock recorded signal inGavardo is represented. The peak value of the spectral acceleration is rather small andthe spectrum exhibits a band concentration of high values for high frequenciesGAVARDO STATION RECORD: ELASTIC SPECTRUM FOR W-ECOMPONENTGAVARDO STATION RECORD: ELASTIC SPECTRUM FOR N-SCOMPONENTSa [cm/s2]1601401201008060402000.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50Period [s]Sa [cm/s2]3002502001501005000.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50Period [s]GAVARDO STATION RECORD: ELASTIC SPECTRUM FOR D-UCOMPONENTSa [cm/s2]1601401201008060402000.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50Period [s]Fig.2.12 Elastic spectrum for the Gavardo station record of the main shock11

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportFinally, in Fig. 2.13 a), the inelastic spectra computed for the main component of themain shock are reported. The corresponding ductility demand is almost negligible, exceptfor high frequencies.GAVARDO STATION ACCELERATION RECORDS: INELASTICSPECTRA FOR N-S COMPONENT1.61.41.2Ductility Demand10.80.60.40.2q=2.77q=4.9500.00 0.50 1.00 1.50 2.00 2.50 3.00Period [s]Fig.2.13 Inelastic spectra for the main component (N-S) of the Gavardo station record ofthe main shock2.5 References1 D. Molin, M. Stucchi & G. Valensise. Massime intensità macroseismiche osservatenei comuni italiani, http://emidius.mi.ingv.it/GNDT/IMAX/imax.html, Dipartimentodella Protezione Civile; 19962 D. Slejko, R. Camassi, I. Cecic, D. Herak, M. Herak, S. Kociu, V. Kouskouna, J.Lapajne, K. Makropoulos, C. Meletti, B. Muco, C. Papaioannou, L. Peruzza, A.Rebez, P. Scandone, E. Sulstarova, N. Voulgaris, M. Zivcic & P. Zupancic. GSHAPseismic hazard assessment for the Adria region, http://seismo.ethz.ch/gshap/adria/,Global Seismic Hazard Assessment Program; 19993 INGV: Istituto Nazionale di geofisica e Vulcanologia, http://www.ingv.it4 M. Baratta, I Terremoti d’Italia, Arnaldo Forni Editore; 19005 INGV: http://www.ingv.it/terremoti/bresciano2004/bresciano.html6 Ordinanza PCM del 20 Marzo 2003, N.32747 http://zonesismiche.mi.ingv.it/mappa_ps_apr04/italia.html8 USGS: http://earthquake.usgs.gov/recenteqs/, Earthquake Hazards Programme,United States Geological Survey; 2002.9 Protezione Civile: http://www.protezionecivile.it/cms/attach/rapporto_garda.pdf12

The Garda Lake (Italy) earthquake of 24 November 2004: A field report3 DAMAGE DISTRIBUTION: OBSERVED MICROSEISMIC INTENSITY3.1 Vulnerability class according to the European macroseismic scaleThe observation of the affected area has shown that the structural damage is concentratedin the historical centers of the villages. There, the prevailing part of the building stockconsisted of two (rarely three) storey non-engineered masonry houses. Having in mindthat a considerable part of these structures during its 200-300 years long exploitation hasbeen subjected to many non-engineered interventions and the observed during the surveycases of structural deficiencies (considered in detail in Chapter 4), vulnerability class A isassigned to these buildings. Vulnerability class B is assigned to the well-constructedmasonry buildings and to the masonry buildings with reinforced concrete (RC) floorswith construction deficiencies. Vulnerability class C is assigned to the well-constructedmasonry buildings with reinforced concrete (RC) floors.The European macroseismic scale (EMS), [1], distinguishes groups of RC structureswithout earthquake resistant design (ERD), with moderate level of ERD and with highlevel of ERD. In the affected area ERD for second category of seismicity has beenrequired since 1974. The buildings were designed for peak ground acceleration of 0.07 g,[2]. According to the recent seismic macrozonation map, [3], an effective groundacceleration of 0.15 g is assigned to the affected area. Having in mind the relatively lowmagnitude of effective ground acceleration of 0.07 g, vulnerability class C is assigned toall RC structures. The quality of construction is not considered when attributing thevulnerability class of the RC buildings, since only one of them had slight non-structuraldamage and no special survey was performed.Since the statistical data about the damage of the buildings were not completed at the timeof the preparation of this report, the evaluation of the amount of the damaged buildings isbased on expert estimation. 710 calls for survey of damaged buildings were received inVobarno (including the associated fractions) and 426 in Sabbio Chiese (including theassociated fractions) as of 1 of December 2004.The European macroseismic scale and the Modified Mercalli scale are reported for thesake of convenience in Annex B.3.2 VobarnoThe few negligibly damaged buildings were concentrated on the deposits along the riverChiese.Very slight non-structural damage was observed in isolated buildings of class A and classB: hair-line cracks in plaster of the walls, as shown in Figures 3.1 and 3.2. A verticalcrack in the masonry wall and fall of plaster was observed in one building, as illustratedin Figure 3.3. Having in mind the above observations EMS intensity of V and ModifiedMercalli intensity of 5 are assigned to the part of Vobarno located along the river.13

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportFigure 3.1. Cracks in the plaster in a churchin VobarnoFigure 3.2. Cracks in the plaster of aBuilding in VobarnoFigure 3.3. Vertical crack in the masonry wall and fall of plaster in Vobarno3.3 Collio (fraction of Vobarno)In Collio many of the masonry buildings of class A and few of class B suffered slightnon-structural damage: hairline cracks in the walls, fall of small pieces of plaster, fall ofloose bricks from the upper parts of the buildings (Figure 3.4). Few of the masonrybuildings of class A suffered cracks in several walls (Figure 3.5) and in isolated casescracking of walls of the structures of class B was observed (Figure 3.6). A failure of awall of structure of class C, provoked by a non-engineered intervention was observed(Figure 4.17). In the RC buildings of class C the separation joints acted, as shown inFigure 3.7. On the basis of the above observations EMS intensity of V/VI and ModifiedMercalli intensity of 6 are assigned to Collio.14

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportFigure 3.4. Fall of loose bricks in CollioFigure 3.5. Cracks in the masonry wallsFigure 3.6. Failure of masonry wallFigure 3.7. Separation joint in RCbuilding3.4 Pompegnino (fraction of Vobarno)Considerable damage of the masonry structures was observed in Pompegnino: failure ofmasonry walls of poor quality (Figure 3.8), out-of-plane deformation and cracking ofmasonry walls (Figure 3.9), failure of masonry due to the lack of separation jointsbetween buildings with different levels of the horizontal elements (Figure 3.10),separation of masonry walls from the RC slab, disintegration and failure of theunconfined masonry under the roof structures (Figure 3.11), cracking of windows piers.The upper part of the church bell tower suffered shear failure, it was cracked considerablydue to pounding with an adjacent building, and the façade walls of the church wereconsiderably cracked in the upper part.15

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportFigure 3.8. Collapsed masonry wall Figure 3.9. Out of planedeformation and cracking of amasonry wallFigure 3.10. Lack of separation jointFigure 3.11. Failure of the masonry underthe roofIsolated buildings of class A suffered damage of grade 3 (see Annex B), many buildingsof class A and few buildings of class B and C suffered damage of grade 2, many buildingsof class B suffered damage of grade 1, isolated buildings of class C (see figure 3.10) alsoexhibited damage of grade 2. As a result of the observations EMS intensity of VI/VIIand Modified Mercalli intensity of 7 are assigned to Pompegnino.3.5 Pavone (fraction of Sàbbio Chiese)The historical centre of Pavone as well as some relatively new buildings sufferedconsiderable damage. There, diagonal cracks in the masonry walls were observed,together with failure of walls with poor quality (Figure 3.12), shear failure of masonrycolumns (Figure 3.13), out-of-plane deformation and cracking of slender masonry walls(Figure 3.14), disintegration and failure of the unconfined masonry under the roof16

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportstructures (Figure 3.15). The external observation of the Pavone church has shown aslight structural damage.Figure 3.12. Failure of masonry with poorqualityFigure 3.13. Shear failure of masonryFigure 3.14. Failure of untied slendermasonry wallFigure 3.15. Failure of the masonry underthe roofMany masonry buildings of class A and few buildings of class B suffered damage ofgrade 2, most buildings of class A and many buildings of class B suffered damage of17

The Garda Lake (Italy) earthquake of 24 November 2004: A field report(Figure 3.17). The church was considerably damaged: the upper part of the bell towersuffered shear failure (Figure 3.18), the masonry was considerably cracked in manyplaces due to interaction with adjacent structures (Figure 3.18), shear effects and out-ofplanebending. Partial separation of the façade walls was observed (Figure 3.19). NearClibbio a rock-fall caused damages of the road (Figure 3.20).The observation has shown that many masonry buildings of class A and few buildings ofclass B suffered damage of grade 2, most buildings of class A and many buildings ofclass B suffered damage of grade 1. Isolated buildings of class C suffered damage ofgrade 2. On this basis EMS intensity of VI/VII and Modified Mercalli intensity of 7/8are assigned to Clibbio.Figure 3.20. Rock-fall near Clibbio3.7 References1. Conseil de l’Europe. European macroseismic scale 1998 (EMS-98). Cahier duCentre Européen de Géodynamique et de Séismologie, G. Gruenthal, editor.Luxemburg; 15, 1998.2. D.M. Min. LLPP 16 Gennaio 1996, “Norme Tecniche per le Costruzioni in ZoneSismiche” (in Italian)3. Norme tecniche per il progetto, la valutazione e l’adeguamento sismico degli edifici.Rome, 2003. (in Italian)19

The Garda Lake (Italy) earthquake of 24 November 2004: A field report20

The Garda Lake (Italy) earthquake of 24 November 2004: A field report4 PERFORMANCE OF BUILDING STRUCTURES4.1 Non-engineered masonry housesThe prevailing part of the residential building stock in the observed affected area consistsof two or three story masonry houses, built before the last World War. The most severelydamaged parts of the villages were the historical centers where the houses are 200-300years old. During their long exploitation they were subjected to many reconstructions,which, together with the building techniques from the past and deterioration of thematerials contributed their seismic vulnerability. As shown in Figure 4.1, the execution ofa large opening in the massive contra-force wall contributed its failure. The infills of thelarger openings separated and cracked, as shown in Figure 4.2. The new-built untiedslender masonry wall in Pavone suffered out-of-plane-deformation and cracked, as shownin Figure 3.14.Figure 4.1. House in Clibbio with a largeopening in the bearing wallFigure 4.2. Separation of infills in CollioThe weak connection of the roof structures with the unconfined masonry caused failure ofthe masonry (Figure 4.3) and, in some cases failure in the roof structure (Figure 4.4) dueto the damaged supports.Figure 4.3. Failure of the unconfinedmasonry under the roof in PompegninoFigure 4.4. Failure of the masonry support andof the roof in Clibbio21

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportThe weak connection of the floor and roof structures with the masonry as well as theinsufficient in-plane stiffness of the floors and roofs did not allow the redistribution of theseismic forces between the individual walls. The walls separated along their joints andsuffered out-of-plane deformation, as shown in Figure 4.5.Figure 4.5. Separation of masonry walls in PavoneFigure 4.6. Irregular structure inClibbioAnother source of failure was the lack of separation joints between the houses. Adjacentstructures with different height of the floors “bumped” against each other causing failureof the masonry in the neighbouring parts, as shown in Figure 4.16 for Collio. Theirregular distribution of the stiffnesses and masses in-plan and along the height provokedfailures in a house in Clibbio, as shown in Figure 4.6. The use of different materials forconstruction of the masonry walls caused their cracking and disintegration. In Figure 4.7the failure of a masonry wall containing bricks and stones with different size is presented.The horizontal seismic loading caused sliding and failure of the ‘coppi’ tiles in manyroofs in Clibbio and Pompegnino, as shown in Figure 3.17 and Figure 4.8.Figure 4.7. Failure of masonry inPavoneFigure 4.8. Sliding of ‘coppi’ tiles in PompegninoIn Pavone, it was observed that old buildings that had even been retrofitted or partiallyrehabilitated shortly before the event suffered structural damage (Fig. 4.9-4.10). This22

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportdamage can be explained by the fact that the rehabilitation interventions had mainly beentargeted to non-structural members and had been designed without taking into properaccount the seismic hazard.Figure 4.9. Renovated house in PavoneFigure 4.10. Renovated house in PavoneThe most heavily damaged parts of the churches in Pompegnino and Clibbio were the belltowers. In the two cases the masonry columns framing the upper part at the level of thebells are heavily sheared, as shown in Figure 4.11 for Clibbio and Figure 4.12 forPompegnino. These heavy damages are caused by the improperly weak cross-sections ofthe masonry columns in comparison with the earthquake-induced inertial forces to theheavy bells, as well as by a torsional unbalance connected with the positioning of thebells with different masses.Figure 4.11. The bell-tower in ClibbioFigure 4.12.The bell-tower in PompegninoThe slender façade walls of the two churches were cracked considerably in many placesdue to shear effects and out-of-plane bending (Figure 4.13 and Figure 4.14). The observed23

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportpartial separation of the façade walls (Figure 3.19 and Figure 4.12) was most probablyprovoked by a weak connection between the walls and the roof.Figure 4.13. The church in ClibbioFigure 4.14. The church in PompegninoThe vault of the church in Clibbio was cracked, as shown in Figure 4.15. The externalobservation of the church in Pavone has shown slight structural damage (Figure 4.16).Figure 4.15. Cracks in the vault of thechurch in ClibbioFigure 4.16. The church in Pavone24

The Garda Lake (Italy) earthquake of 24 November 2004: A field report4.2 Engineered structures4.2.1 Masonry structures with reinforced concrete slabsMasonry structures with RC slabs suffered much less damage than non-engineeredmasonry structures.Figure 4.17. Irregular structure in PavoneThe RC slabs tied together the masonry walls and redistributed the horizontal loadingbetween them. The most common failures were cracking of the plaster and fall of smallpieces of it. Nevertheless, in isolated cases, masonry structures with RC slabs sufferedmore substantial damage. In a house in Pavone, the lack of separation joint between thehouse and the associated structure created an irregular ‘united’ structure and, as aconsequence the masonry in the second story of the house was damaged, as well as astone masonry column of the penthouse failed in shear (Figure 4.17). The lack ofseparation joint between adjacent buildings caused failure of the masonry around thefloors of the neighbouring building (Figure 4.18). Non-engineered interventions were alsothe cause of damage in the masonry structures with RC slabs. The failed thin masonrywall (Figure 4.19) observed in Collio most probably has been added to the structureduring the reconstruction of the former garage in a room.25

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportFigure 4.18. Pounding of adjacentbuildings in CollioFigure 4.19. Failed thin masonry wall inCollioThe quality of the masonry contributed substantially the damage of the walls. The poorquality of the workmanship caused the failure of the masonry wall shown in Figure 4.20.The hollow bricks with a small net cross-sectional area and insufficient thickness of thecross web and face shells used in some walls turned out to have much lower strength thanthe mortar (Figure 4.21).Figure 4.20. Cracked masonry wall inPompegnino4.2.2 Reinforced concrete structuresFigure 4.21. Hollow bricks used inPompegninoNo major damage was observed in RC structures. The separation joints acted in somebuildings, as shown in Figure 3.7. A slight non-structural damage was observed only inan irregular RC building in Collio, where masonry walls separated from the RC frame.The irregularity was created by the absence of masonry walls in a considerable part of thefirst story in connection with its exploitation as a workshop (Figure 4.22). The absence ofmasonry walls in this part affected torsional unbalance and to a certain extent a ’soft firststorey’. The resulted separations of the masonry walls in the second storey and in thefirst storey are shown in Figure 4.22 and Figure 4.23, respectively.26

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportFigure 4.22. Irregular building in CollioFigure 4.23. Separation of masonry wallsThe lack of separation joints between RC buildings and older structures created poundingeffects. The single-storey RC structure heavily damaged the adjacent masonry building inPompegnino, as shown in Figure 4.24.Figure 4.24. Pounding of adjacent structures in Pompegnino4.3 ConclusionThe observation has shown that structures of good quality that had been properlydesigned for non-seismic conditions did not suffer structural damage. On the other hand,the earthquake caused significant damage to non-engineered masonry residentialbuildings and churches. The most severely damaged parts of the villages were thehistorical centres where the houses are 200-300 years old. The weak connection of themasonry walls with the roof and floor structures, the poor quality of workmanship andbricks, the lack of separation joints, the irregularities of the structures and the improper27

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportreconstructions were the main sources of structural damage. The presence of ties in animportant part of the existing masonry buildings prevented their partial collapse.Finally, it was observed that even old buildings that had been retrofitted or partiallyrehabilitated shortly before the event suffered structural damage. This was due to the factthat the rehabilitation interventions had mainly been targeted to non-structural membersand had been designed without taking into proper account the seismic hazard.28

The Garda Lake (Italy) earthquake of 24 November 2004: A field report5 SOCIO-ECONOMIC EFFECTS AND EMERGENCY MANAGEMENT5.1 GeneralThe emergency situation in the Garda area was managed by a number of operatorsrepresenting different governative or non-governative agencies and institutions,coordinated by Protezione Civile (Emergency Management Unit of the ItalianGoverment), [1]. The centres where the field authority was concentrated wereimmediately established in some nevralgic small villages of the area. The main centre wasthe C.O.M. (the acronym for “Centro Operativo Misto”, translation of Multi-taskingOperational Centre) arranged in Salò. As the name says, this kind of centre has theauthority to operate in the emergency dealing with all possible kinds of problems. TheSalò C.O.M. became active in the first hours after the event and was still operational atthe time of the field mission (one week after the event). The main emergencies had allbeen dealt with, but no prevision on the date of dismantling of the Centre was anticipated.The C.O.M., retaining the decisional power and the majority of contacts with the externalinstitutions, was at first established in the Auditorium of the Secondary School of Salòand later moved to the Gymnasium of the same building, due to the need of more room toaccommodate the different operative units. Other operative centres were established in themost severely stricken villages: they were named C.O.As, acronym for (“CentroOperativo Avanzato, meaning they were right on the spot where most of the damage andemergency intervention requests were concentrated). The C.O.A. that was visited duringthe field mission was located in Pompegnino, fraction of Vobarno.The functions of the C.O.M.s and, subordinately, of the C.O.A.s are several:• Assistance to Local Authorities• Damage estimation• Administrative support• Transportation and road management• Public safety• Historical and cultural monuments preservation• Information and public relations• Urgent technical services and dangerous materials• Scientific research and planning• Public health• Evacuation and logistics• Volunteering coordination• Telecommunications• General secretariatDuring the field mission contacts were taken with the Mayor of Vobarno, who was sokind as to personally give the ELSA team a picture of the damage distribution in hisvillage and the relevant statistics for Vobarno, reported in the following. Moreover, hegranted our team access to the fraction of Pompegnino, which had suffered the mostsignificant damage, so that contact could be taken with Mr. Cadenelli from the localC.O.A., who led the team on a tour of the village to gather the photographicdocumentation reported above.29

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportFigure 5.1. The Salò C.O.M.Figure 5.2. Map of the requested and performedstructural safety assessment interventions at theSalò C.O.M.Figure 5.3. The Pompegnino C.O.A.Figure 5.4. The Pompegnino camp kitchenand canteenDuring the visit to the Salò C.O.M. contacts were taken with volunteers from RegioneLombardia, who were very helpful in providing us with the general statistics of the safetyassessment interventions for the area, as reported in the following.Moreover, contacts were taken with Professor Riva from the University of Brescia, whowas also visiting the area with the task of estimating the safety of the building stock.5.2 Statistics5.2.1 Emergency operationsThe emergency interventions in the area seemed appropriate, as for timing and efficiency.Starting from the very early hours after the event, Italian Protezione Civile took action:Vigili del Fuoco (Fire Brigade) and the Police were sent to the affected areas and damageemergency surveys were carried out. The C.O.M. was immediately set up in Salò.Regione Lombardia took charge of the management of the structural safety assessment30

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportinterventions, carried out by qualified experts from the Municipalities and from theLombardia Region together with Vigili del Fuoco. The Police (Forze dell’Ordine, whichin Italy are represented by different corps, Carabinieri, Polizia di Stato and Guardia diFinanza) and the Italian Army, represented by the Alpini Corp, also had key roles in theinitial phases of the emergency.Moreover, according to the information received at the Salò C.O.M., a total of 300volunteers were present, mainly from Lombardia, who provided useful and very effectivehelp in all the operational tasks. The Italian Red Cross provided volunteers too.As of the day of the visit, no official statistics were available regarding the emergencyinterventions and the damage survey and estimation. Anyhow, partial statistics wereprovided by the Salò C.O.M., about the intervention requests, performed safetyverifications and certified damage in the 62 Municipalities involved in the emergency.Table 5.1. Assisted population in the most damaged villagesEvacuatedPop.Village Pop. InterventionRequestsDamage to publicBuildingsVobarno (Total) 7600 720 170 Primary School (Partial),Churches in Pompegninoand Carpeneda (Severe)Sabbio Chiese 3172 426 125 Municipality (Partial)Primary School,Kindergarten (Severe)Salò 10056 1612 330 Primary and SecondarySchool, Kindergarten(Partial), some roadsclosedVillanuova sulClisi4776 345 29 Municipality (Severe),Primary SchoolToscolano 7004 214 25 Some roads interruptedMadernoRoe’ Volciano 4174 500 127 All the ChurchesTotal (62Municipalities)/ 6070 1187(Severe)In Tab. 5.1, the data for the most affected villages are reported; in the last row the totaldata for all the 62 Municipalities are given (the data on the population were taken from[2]).In Annex A the official document for the request of intervention, that had to be filled inby the inhabitants of the damaged buildings, can be found.5.2.2 Damage and economic lossesAt present, no economic estimation of the damage has been carried out yet. At the time ofthe visit, Regione Lombardia and the Italian Government had allocated 10 million Euroseach, for the emergency and urgent interventions. Further economic help to the affectedMunicipalities was foreseen as soon as reliable estimations of the needed interventionswill be available.31

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportA sample of the emergency safety interventions carried out on buildings at risk of partialfailure are reported in Fig. 5.5-5.10.Figure 5.5. Safety intervention on a stonemasonry wallFigure 5.6. Vigili del Fuoco intervening on theroof of a damaged building in PompegninoFigure 5.7. Vigili del Fuoco vehicles inPompegninoFigure 5.8. Vigili del Fuoco working on theroof of the heavily damaged church in ClibbioFigure 5.9. Intervention on a severely damagedbuilding in PompegninoFigure 5.10. Safety intervention in Collio32

The Garda Lake (Italy) earthquake of 24 November 2004: A field report5.3 References1. Protezione Civile, http://www.protezionecivile.it/2. Comuni Italiani, http://www.comuni-italiani.it33

The Garda Lake (Italy) earthquake of 24 November 2004: A field report34

The Garda Lake (Italy) earthquake of 24 November 2004: A field report6 CONCLUSIONSThe earthquake of 24 November 2004 was an event of average relevance, with no majorfeatures of intensity, damage caused or casualties.The impact of the event was thus mainly confined at a local level. Damage of a certainextent developed only in older masonry structures, without engineered lateral loadresistance and built with poor technology and bad quality workmanship.Old constructions, such as 200- or 300-year-old houses or churches, suffered significantdamage: this was probably the worst consequence of the earthquake, in terms of localheritage.The warning that must be once again derived from such an event is on the seismicinadequacies of a relatively vast number of housing buildings, even in otherwise welldevelopedareas of Italy. The effects of good workmanship and structural detailing (suchas the presence of ties) in avoiding major collapse even in relatively poor structures werealso made clear; on the contrary, poor structural detailing and careless repair and/orchange-of-use interventions turned out to be a major source of vulnerability, even forrelatively good structures. Moreover, it was observed that even old buildings that hadbeen retrofitted or partially rehabilitated shortly before the event suffered structuraldamage. This was due to the fact that the rehabilitation interventions had mainly beentargeted to non-structural members and had been designed without taking into properaccount the seismic hazard.As for the impact on population, though, even if no casualties were originated by theevent, the feeling of local authorities was that the importance of the consequences for asignificant part of the local people was underrated or thoroughly neglected by the mediawhich, to a certain extent, made it even more difficult for them to cope with the lossesand the troubles.This report is mainly intended to contributing towards a better understanding anddocumentation of the impact of the event from an engineering point of view, with theadditional hope that, through this, a more objective and comprehensive picture of thelocal situation will be drawn.35

The Garda Lake (Italy) earthquake of 24 November 2004: A field report36

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportANNEX APost-earthquake damage evaluation forms, as provided by Italian Protezione Civile.37

The Garda Lake (Italy) earthquake of 24 November 2004: A field report38

The Garda Lake (Italy) earthquake of 24 November 2004: A field report39

The Garda Lake (Italy) earthquake of 24 November 2004: A field report40

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportANNEX BEUROPEAN MACROSEISMIC INTENSITY SCALEClassifications used in the European Macroseismic Scale (EMS)Differentiation of structures (buildings) into vulnerability classes(Vulnerability Table)The masonry types of structures are to be read as, e.g., simple stone masonry, whereas thereinforced concrete (RC) structure types are to be read as, e.g., RC frame or RC wall.See section 2 of the Guidelines and Background Materials for more details, also withrespect to the use of structures with earthquake resistant design.Classification of damage41

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportNote: the way in which a building deforms under earthquake loading depends on thebuilding type. As a broad categorisation one can group together types of masonrybuildings as well as buildings of reinforced concrete.Classification of damage to masonry buildingsGrade 1: Negligible to slight damage(no structural damage,slight non-structural damage)Hair-line cracks in very few walls.Fall of small pieces of plaster only.Fall of loose stones from upper parts ofbuildings in very few cases.Grade 2: Moderate damage(slight structural damage, moderatenon-structural damage)Cracks in many walls.Fall of fairly large pieces of plaster.Partial collapse of chimneys.Grade 3: Substantial to heavy damage(moderate structural damage,heavy non-structural damage)Large and extensive cracks in most walls.Roof tiles detach. Chimneys fracture at the roofline; failure of individual non-structuralelements (partitions, gable walls).Grade 4: Very heavy damage(heavy structural damage,very heavy non-structural damage)Serious failure of walls; partial structuralfailure of roofs and floors.42

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportGrade 5: Destruction(very heavy structural damage)Total or near total collapse.Classification of damage to buildings of reinforced concreteGrade 1: Negligible to slight damage(no structural damage,slight non-structural damage)Fine cracks in plaster over frame members orin walls at the base.Fine cracks in partitions and infills.Grade 2: Moderate damage(slight structural damage,moderate non-structural damage)Cracks in columns and beams of frames and instructural walls.Cracks in partition and infill walls; fall ofbrittle cladding and plaster. Falling mortarfrom the joints of wall panels.Grade 3: Substantial to heavy damage(moderate structural damage,heavy non-structural damage)Cracks in columns and beam column joints offrames at the base and at joints of coupledwalls. Spalling of conrete cover, buckling ofreinforced rods.Large cracks in partition and infill walls,failure of individual infill panels.Grade 4: Very heavy damage(heavy structural damage,very heavy non-structural damage)Large cracks in structural elements with43

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportcompression failure of concrete and fracture ofrebars; bond failure of beam reinforced bars;tilting of columns. Collapse of a few columnsor of a single upper floor.Definitions of quantityGrade 5: Destruction(very heavy structural damage)Collapse of ground floor or parts (e. g. wings)of buildings.Definitions of intensity degreesArrangement of the scale:a) Effects on humansb) Effects on objects and on nature(effects on ground and ground failure are dealt with especially in Section 7)c) Damage to buildingsIntroductory remark:The single intensity degrees can include the effects of shaking of the respective lowerintensity degree(s) also, when these effects are not mentioned explicitly.I. Not felta) Not felt, even under the most favourable circumstances.b) No effect.c) No damage.44

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportII. Scarcely felta) The tremor is felt only at isolated instances (

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportc) Damage of grade 1 is sustained by many buildings of vulnerability class A and B; afew of class A and B suffer damage of grade 2; a few of class C suffer damage of grade 1.VII. Damaginga) Most people are frightened and try to run outdoors. Many find it difficult to stand,especially on upper floors.b) Furniture is shifted and top-heavy furniture may be overturned. Objects fall fromshelves in large numbers. Water splashes from containers, tanks and pools.c) Many buildings of vulnerability class A suffer damage of grade 3; a few of grade 4.Many buildings of vulnerability class B suffer damage of grade 2; a few of grade 3.A few buildings of vulnerability class C sustain damage of grade 2.A few buildings of vulnerability class D sustain damage of grade 1.VIII. Heavily damaginga) Many people find it difficult to stand, even outdoors.b) Furniture may be overturned. Objects like TV sets, typewriters etc. fall to the ground.Tombstones may occasionally be displaced, twisted or overturned. Waves may be seen onvery soft ground.c) Many buildings of vulnerability class A suffer damage of grade 4; a few of grade 5.Many buildings of vulnerability class B suffer damage of grade 3; a few of grade 4.Many buildings of vulnerability class C suffer damage of grade 2; a few of grade 3.A few buildings of vulnerability class D sustain damage of grade 2.IX. Destructivea) General panic. People may be forcibly thrown to the ground.b) Many monuments and columns fall or are twisted. Waves are seen on soft ground.c) Many buildings of vulnerability class A sustain damage of grade 5.Many buildings of vulnerability class B suffer damage of grade 4; a few of grade 5.Many buildings of vulnerability class C suffer damage of grade 3; a few of grade 4.Many buildings of vulnerability class D suffer damage of grade 2; a few of grade 3.A few buildings of vulnerability class E sustain damage of grade 2.X. Very destructive46

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportc) Most buildings of vulnerability class A sustain damage of grade 5.Many buildings of vulnerability class B sustain damage of grade 5.Many buildings of vulnerability class C suffer damage of grade 4; a few of grade 5.Many buildings of vulnerability class D suffer damage of grade 3; a few of grade 4.Many buildings of vulnerability class E suffer damage of grade 2; a few of grade 3.A few buildings of vulnerability class F sustain damage of grade 2.XI. Devastatingc) Most buildings of vulnerability class B sustain damage of grade 5.Most buildings of vulnerability class C suffer damage of grade 4; many of grade 5.Many buildings of vulnerability class D suffer damage of grade 4; a few of grade 5.Many buildings of vulnerability class E suffer damage of grade 3; a few of grade 4.Many buildings of vulnerability class F suffer damage of grade 2; a few of grade 3.XII. Completely devastatingc) All buildings of vulnerability class A, B and practically all of vulnerability class C aredestroyed. Most buildings of vulnerability class D, E and F are destroyed. The earthquakeeffects have reached the maximum conceivable effects.47

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportModified Mercalli ScaleAverage peakvelocity(centimetersper second)Intensity value and descriptionI. Not felt except by a very few under especiallyfavorable circumstances.(I Rossi-Forel scale)II. Felt only by a few persons at rest, especiallyon upper floors of buildings. Delicatelysuspended objects may swing.(I to II Rossi-Forel scale)III. Felt quite noticeably indoors, especially onupper floors of buildings, but many people do notrecognize it as an earthquake. Standingautomobiles may rock slightly. Vibration likepassing of truck. Duration estimated.(III Rossi-Forel scale)Average peakacceleration (g isgravity=9.80meters per secondsquared)1-2 IV. During the day felt indoors by many,outdoors by few. At night some awakened.Dishes, windows, doors disturbed; walls makecreaking sound. Sensation like heavy truckstriking building. Standing automobiles rockednoticeably.(IV to V Rossi-Forel scale)2-5 V. Felt by nearly everyone, many awakened.Some dishes, windows, and so on broken; crackedplaster in a few places; unstable objectsoverturned. Disturbances of trees, poles, and othertall objects sometimes noticed. Pendulum clocksmay stop.(V to VI Rossi-Forel scale)5-8 VI. Felt by all, many frightened and run outdoors.Some heavy furniture moved; a few instances offallen plaster and damaged chimneys. Damageslight.(VI to VII Rossi-Forel scale)8-12 VII. Everybody runs outdoors. Damagenegligible in buildings of good design andconstruction; slight to moderate in well-builtordinary structures; considerable in poorly builtor badly designed structures; some chimneys0.015g-0.02g0.03g-0.04g0.06g-0.07g0.10g-0.15g48

The Garda Lake (Italy) earthquake of 24 November 2004: A field reportbroken. Noticed by persons driving cars.(VIII Rossi-Forel scale)20-30 VIII. Damage slight in specially designedstructures; considerable in ordinary substantialbuildings with partial collapse; great in poorlybuilt structures. Panel walls thrown out of framestructures. Fall of chimneys, factory stack,columns, monuments, walls. Heavy furnitureoverturned. Sand and mud ejected in smallamounts. Changes in well water. Persons drivingcars disturbed.(VIII + to IX Rossi-Forel scale)45-55 IX. Damage considerable in specially designedstructures; well-designed frame structures thrownout of plumb; great in substantial buildings, withpartial collapse. Buildings shifted off foundations.Ground cracked conspicuously. Undergroundpipes broken.(IX + Rossi-Forel scale)More than 60X. Some well-built wooden structures destroyed;most masonry and frame structures destroyedwith foundations; ground badly cracked. Railsbent. Landslides considerable from river banksand steep slopes. Shifted sand and mud. Watersplashed, slopped over banks.(X Rossi-Forel scale)XI. Few, if any, (masonry) structures remainstanding. Bridges destroyed. Broad fissures inground. Underground pipelines completely out ofservice. Earth slumps and land slips in softground. Rails bent greatly.XII. Damage total. Waves seen on groundsurface. Lines of sight and level distorted. Objectsthrown into the air.0.25g-0.30g0.50g-0.55gMore than 0.60gBolt, Bruce A. Abridged Modified Mercalli Intensity Scale, Earthquakes - Newly Revisedand Expanded, Appendix C, W.H. Freeman and Co. 1993, 331 pp.49