L’Aquila Earthquake April 6th, 2009: the Damage Assessment Methodologies

1 INTRODUCTION

An earthquake of magnitude MW=6.3 (9 km shallow focal depth) struck the Abruzzo Region in Central Italy on the early morning (03:32 local time) of 6th April 2009. The epicenter was very close to the city of L'Aquila (sources: INGV, http://portale.ingv.it/; USGS, http://www.usgs.gov/). The starting point of the seismic sequence is considered to be the March 30th, with a MW=4.4 event, though several small shocks had been recorded before. The MW=6.3 main event has been followed by several aftershocks, the major of which occurred on April 7th (MW=5.6). The number of casualties was 306 and the injured people approximately 1500. The area affected by the earth-quake includes L'Aquila city center, the suburbs and some villages in the region, and many buildings were severely damaged or collapsed. Old buildings and more recent constructions, were unable to with-stand the intensive shaking that occurred close to the rupture fault. The earthquake caused many losses and damage (about 18000 unusable buildings) in the most affected area (Indirli, 2010).

An extensive damage survey of the whole historic centre of L’Aquila was conducted by the PLINIVS centre after the earthquake, with the contribution of M. Indirli (ENEA, Italy), R.P. Borg (University of Malta, Malta) and L.A. Kouris (University of Thes-saloniki, Greece), experts from COST Action C26,

Urban Habitat Constructions under Catastrophic Events (COST C26). The COST researchers, in ad-dition to an overall review of the consequences of the earthquake in L’Aquila and its surroundings, contributed to the aforementioned work, through a detailed investigation of various areas, including ar-eas of the historic city centre. Various methods were adopted during the surveys to assess the damage, in-cluding the following developed in the framework of the Italian Civil Protection Activities: AeDES & AeDES Modified (“Scheda di I livello di rile-vamento danno, pronto intervento e agibilità per edi-fici ordinari nell’emergenza post-sismica/First level form for safety assessment, damage investigation, prompt intervention for ordinary buildings in the post-earthquake emergency; Protezione Civile 2010a); MEDEA (“Manuale di Esercitazioni sul Danno Ed Agibilità/User’s manual on damage and safety for ordinary buildings”; MEDEA 2005).

The Earthquake Engineering and Field Investiga-tion Team (EEFIT) is a group of UK engineers and academics that organises field missions in the im-mediate aftermath of earthquakes in order to gather data on the performance of structures, foundations, services etc. EEFIT was formed in 1982 and has been carrying out regular investigations of earth-quake damage ever since. Following the Aquila earthquake a reconnaissance team sent by EEFIT and led by T. Rossetto visited the affected area

L’Aquila Earthquake April 6th, 2009: the Damage Assessment Methodologies

R. P. Borg Department of Building & Civil Engineering, University of Malta, Malta

M. Indirli ENEA, Italian National Agency for New Technologies, Energy and Sustainable Economic Development, Italy

T. Rossetto Department of Civil, Environmental & Geomatic Engineering, University College London, U.K.

L.A. Kouris Department of Civil Engineering, Aristotle University of Thessaloniki, Greece

ABSTRACT: Different Methodologies were adopted during the field investigations and the assessment of damage in structures following the Abruzzo (Italy) Earthquake of the 6th April 2009. The scope of the paper is to review the different methodologies adopted by the COST Action C26 Field Investigation Team, and the methodologies considered by the EEFIT Team in the field assignments conducted in the aftermath of the earthquake. The COST C26 team based the assignment on a number of methodologies: the AeDES (AeDES & AeDES Modified) and the MEDEA, used by the Italian Civil Protection for Masonry and Reinforced Con-crete structures; the EEFIT team methodology included the general observations, the rapid survey using EMS-98, and the detailed survey. The aim of the paper is to review the methods, assess the type and extent of data collected and the scale considered, and analyse each methodology with respect to the scope of the tasks undertaken. A critical assessment of the methods, is presented with respect to the varying parameters includ-ing the scale and detail of assessment, the structure type, and the evaluation criteria for risk and conformity.

(EEFIT 2009). The Methodology adopted included the general observations, rapid survey using EMS-98, and the detailed survey.

2 DATA COLLECTION & MANAGEMENT

2.1 Classification of Data Collection Methods The data collection methods concerning structural damage can be classified in accordance to the scope of the survey, the discipline considered, the time of data collection, the accuracy of data collection, and the amount of the data collected. Many of the above are correlated; the damage assessment methods can be classified with respect to the scope, the discipline and the time of data collection (Goretti et al. 2002). The Scope: short term usability assessment; assess-ment of economic losses or required funds for re-construction; evaluation of individual contributions; social impact assessment; prevention and emergency management; scientific purposes. The Discipline: geosciences; structural engineering - buildings; structural engineering - other systems; so-cial sciences; economy and overall impact of the seismic event. The Time of data collection: pre-event; post event (preliminary macroseismic intensity assessment 2-3 days, reconnaissance survey 2-3 weeks); post event (usability & damage assessment Level I accuracy, 3-60 days); post event (Level III accuracy, 30 days - some years).

Pre-event data collection: Systematic typological, dimensional and functional data collection of build-ings can be conducted, and result in an inventory based on technical information on buildings on a re-gional or national level.

Post-event data collection methods, and usabil-ity/damage evaluation, are considered the major source of information in Italy, Turkey and Japan. (Goretti et al. 2002). In the evaluation of method-ologies used for data collection, a distinction is made between usability and damage survey. The post-seismic event usability assessment is intended to evaluate the possible short term use of the build-ing. During the assessment, the buildings that can be safely used are identified and emergency measures are implemented in order to reduce risk for people.

The post-earthquake damage evaluation is carried out for a variety of reasons. It is reported that in Ja-pan the aim of the damage assessment is to evaluate the long term use of the building, and the evaluation includes recommendations concerning repair and retrofit, or demolition. In Italy the assessment had a similar scope in the past. However, today the dam-age data collection survey is performed together with the usability survey, and the main purpose is to evaluate the usability, and the overall amount of di-rect economic loss. This is important to assess the financial contributions by the government for the re-

construction. The decision on long-term use of the building is addressed through an engineering evalua-tion in the reconstruction process. In Greece the fi-nancial contributions are based on the usability clas-sification, while in Turkey the damage classification is used to assign the financial contribution to each building (Goretti et al. 2002). The advantage of a joint damage and usability survey, as conducted in Italy, is considered to speed up the overall survey and the reconstruction process. While the comple-tion of the usability survey is slowed down, much of the data collected in the damaged survey is required to be taken into account also in the usability survey. In addition the slow down is compensated by the fact that the usability and damage survey is con-ducted in two steps, with a limited percentage of buildings requiring the second inspection.

The post earthquake damage/usability evaluation needs to take account of the following; the seismic event is not over, and the assessment is valid until a new shock occurs; both cumulative damage and soil motion are recorded for each shock;

a large number of inspections is required; there-fore, the inspection management should be effec-tive;

the inspections should be completed over a short period of time, in order to reduce the risk for the inhabitants (with respect to usability assessment) and to accelerate the reconstruction process (dam-age assessment).

2.2 Data Collection and Data Management As a result of the large amount of buildings to be quickly surveyed in a post-earthquake assessment, only level I information is collected (Goretti et al. 2002). The data cannot be used for an engineering assessment (level II and level III), but can be statis-tically processed and analysed, recording data useful for the usability assessment and the estimate of re-pairs (economic losses), in addition to social data. All this information should be required in detail: identification of the building; dimensional data (area, storey number, height); function (use of the building, number of dwellings and number of inhabitants);

building type (materials, structural systems, age of construction, maintenance);

soil and geomorphology; building damage (levels of damage and extent in different components, overall measure of the damage);

social data (homeless and people evacuated); quality of the inspection, whether complete, par-tial, exterior only;

usability assessment; remarks and observations. In order to obtain reliable data, it is necessary to

reduce subjectivity; therefore, clear methods, unam-

biguous data collection forms (detailed and easy to compile), and well trained inspectors are required. In the data collection, the assessment of component performance is preferred to the component descrip-tion. The accuracy of the data is related to the accu-racy of the inspection, and it is recommended that buildings should not be inspected only from the ex-terior. The processing should allow for checks on the data collected. The management of the data is an important consideration, and includes the data proc-essing, the validation of the data input and mainte-nance. In this regard, the use of GIS systems and pre-event databases help accelerate the data process-ing and validation. Dissemination and easy access to the data are important considerations, and depend on the users including researchers, the purpose of use of the data, and the type of data required.

3 STRUCTURAL DAMAGE ASSESSMENT

The structural damage assessment after a seismic event provides important data for understanding the building’s response. Other indispensable post-earthquake information is the construction’s usabil-ity, in order to identify prompt interventions. The AeDES (Protezione Civile 2010a) and the MEDEA (MEDEA 2005) survey methodologies, specifically developed in Italy to this purpose, were utilised to-gether in L’Aquila immediately after the earthquake, with other assessment tools, during the COST C26 post-event field investigations.

The AeDES (both AeDES and AeDES Modified) level I form is intended for the post-earthquake in-tervention in Italy (Protezione Civile 2002 and 2010a). The aim is to carry out a damage survey in the ordinary structures, check their usability, and de-termine the required emergency actions.

The MEDEA tool is designed to support earth-quake damage assessment in Italy (MEDEA 2005). However, it can possibly be used in regions with similar structures. Its scope is to carry out an objec-tive evaluation of damage, in particular with respect to masonry and reinforced concrete (r.c.) structures, evaluating also the associated failure/damage mechanisms. A variety of damage types are identi-fied and linked to the corresponding mechanisms.

4 THE AeDES LEVEL I SURVEY

The AeDES level I survey of damage, emergency action and usability for ordinary buildings in the post-seismic event (Protezione Civile 2002 and 2010a) is a comprehensive form used for data col-lection in the field, with respect to specific buildings damaged by earthquakes. Its structure is based on a number of sections, as indicated below. Section 1: building identification; section 2: building description;

section 3: structural typology (masonry and r.c.); section 4: damage of structural elements and com-pleted emergency interventions;

section 5: damage of non-structural elements and completed emergency interventions;

section 6: danger due to external/adjacent struc-tures and completed emergency interventions;

section 7: geotechnics and foundation; section 8: evaluation on the structure usability and emergency action;

section 9: remarks and observations. For each structural system (masonry and r.c.), dif-

ferent typologies are identified, with respect to mate-rials, construction technology and detailing. The damage assessment of structural elements is carried out with respect to a matrix, taking account of the structural elements, and considering for each the level of damage, and emergency action completed; the same data collection is carried out also with re-spect to non structural elements. Furthermore, dan-ger due to neighbouring structures, geotechnics and conditions of foundations is also evaluated.

As already said, the AeDES form requires the evaluation of usability. The risk evaluation is carried out using a matrix which assigns a level of risk (from high risk to low risk), according to the damage observed in structural/non-structural elements and foundations, in addition to the danger posed by neighbouring structures. The outcome is expressed on a scale from A to F, where: A means “fit for use (safe)”, B “fit for use with prompt interventions”, C “partially fit for use”, D “not fit for use, necessity of a deeper analysis”, E “not fit for use (unsafe)” and F “not fit for use, due to risk from neighbouring struc-tures”. The form also allows for suggestions for emergency action to be completed on the building.

5 THE MODIFIED AeDES LEVEL I SURVEY

The Modified AeDES Level I survey follows, in principle, the AeDES methodology, with some im-portant modifications to specific sections of the data collection survey sheet. In particular, the AeDES Modified Form shows the following changes: - section 3 has been updated and divided into two

main distinct parts (Masonry and Reinforced Con-crete structures);

- section 4 refers to the damage of structural ele-ments and completed emergency interventions, which is in general similar to the AeDES form; the section related to the damage of non structural elements has been synthesised, but refers to the presence or otherwise of the damage; the AeDES Modified form includes an additional part in sec-tion 4, referring to the summary of damage with respect to the EMS 98, both for the single compo-nents of the building (structural and non-structural) and also for the building as a whole;

the level of damage varies between level 0 (no damage) to level 5 (total collapse);

- the part of section 6 in the AeDES form, referring to the danger due to external/adjacent structures and completed emergency interventions, has been removed in the AeDES Modified;

- in addition, section 8, referring to the assessment of usability of the structure, has been removed in the AeDES Modified; however, the part of section 8 referring to the accuracy of the visit is retained, and included in section 9 of the AeDES modified form;

- section 9 includes also general remarks and obser-vations.

6 CULTURAL HERITAGE METHODOLOGY

Cultural heritage buildings (Linee Guida 2006) can be studied by decomposing the entire structure into architectural portions characterized by an autono-mous structural behaviour with respect to the con-struction as a whole. In fact, in historic complexes, effective connections between vertical walls and floors are often scarce or absent, leading to specific mechanisms (global/local collapse and/or damage) caused by loss of equilibrium of masonry portions under out-of-plane actions. In addition, also in-plane actions are evaluated. The earthquake damage and structural vulnerability of churches is assessed through a specific survey form (Protezione Civile 2010b), in which failure/collapse mechanisms are identified with a similar methodology as told before. The nature and the level of damage is assessed. The damage index is evaluated on the basis of the mechanisms and level of damage recorded. A simi-lar approach is used for monumental buildings (Pro-tezione Civile 2010c).

7 THE MEDEA DAMAGE ASSESSMENT TOOL 7.1 Introduction The structural damage assessment after an earth-quake provides important information for the under-standing of the construction response to the seismic event. The evaluation needs to be based on criteria and methods that can guarantee an objective evalua-tion of the damage, in order to find the best correla-tion between the parameters measuring the seismic action, and the damage in the structures. In fact, po-tential uncertainties and ambiguities can result either in the definition of the level of damage to be consid-ered or in the identification of the damage by the op-erators working in the field after the event. The op-erators are required to take important decisions during the post-event emergency activity, with re-gards the safety of the buildings. Consequently, the identification of objective methodologies, that can serve as tools in the damage evaluation and in the

determination of levels of safety, is of fundamental importance.

7.2 MEDEA: seismic damage evaluation.

The MEDEA tool (MEDEA 2005) is designed to support earthquake structural damage evaluation in Italy, with respect to masonry and r.c. structures, but can also be used effectively for pre-earthquake as-sessment. MEDEA drives to the definition and iden-tification of several damage/failure mechanisms as-sociated to an earthquake. Therefore, structural damage can be linked to the related mechanisms. This results in a better safety assessment, a more homogeneous evaluation of damage across the af-fected area and an improvement of the damage sta-tistics obtained in the assessment. MEDEA is in-tended to derive the most frequent damage typologies in masonry and r.c. structures, and a pos-sible damaging model for a rapid assessment of safety. In fact, the damage assessment protocol is supported by forms where every damage type is de-scribed with notes, diagrams representing different damage levels, and possible links to their associated collapse mechanisms. This approach helps to reduce the level of uncertainty in the assessment of safety during the survey (Papa et al. 2004 ).

MEDEA contains a technical glossary, a picture archive, and a section describing seismic damage analyses, which are also linked to compatible col-lapse mechanisms. It also refers to examples of damage surveys and safety evaluations. MEDEA is mainly intended for the surveyors involved in safety assessment or active in the post event macro-seismic evaluation. The judgment of the surveyor, who needs special training, is a very important factor for the success of the whole procedure, because of the scientific aspects resulting from an assessment of the damage. This is considered important for the im-provement of the vulnerability function, and for a wider harmonization in the definition of macro-seismic fields. The judgement is also important with respect to other considerations concerning the fair estimate of damage and fair evaluation of safety.

7.3 The collapse mechanisms

MEDEA includes a detailed catalogue of the main damage types encountered in structural and non-structural elements in masonry and r.c. buildings. The damage classification of the masonry structures is supported by linking the earthquake damage to the possible collapse mechanisms induced in the building. Therefore, the catalogue is organized such that it ad-dresses the identification of the probable mechanism (Papa et al. 2004). This is supported through the Col-lapse Mechanisms table and the Damage Classifica-tion table. The Collapse Mechanisms table is a sum-mary datasheet which includes the classification of

the main recognisable collapse mechanisms for a standard construction. A similar procedure is fol-lowed for r.c. structures. The above said mechanisms are firstly classified as: global mechanisms; local mechanisms. Global mechanisms are those mechanisms involv-

ing the structures as a whole, and related to the evolu-tion of the cracks in a sufficient number of elements, such that the static and dynamic equilibrium of the structural system is compromised.

Local mechanisms refer to marginal parts of the construction; their evolution, even if it determines the collapse of a single element, generally does not in-volve the equilibrium of the whole structure.

7.4 Masonry structures: damage mechanisms.

The global mechanisms are subdivided as follows. In-plane mechanisms: they occur when the classical

diagonal X cracks appear as a consequence of the formation of diagonal compressive forces in the walls of the masonry box, excited by in-plane actions in both directions; these mechanisms are due to the poor tensile strength of the masonry.

Out-of-plane mechanisms: they appear through an out-of-plane movement of one or more walls of the masonry box, due to failure of the connection be-tween the walls of the facade and the orthogonal ones, as a result of the seismic forces; this is possibly en-hanced through the thrust of heavy floors and roofs.

Figure 1. MEDEA: Global Collapse Mechanisms (masonry).

Figure 2. MEDEA: Local Collapse Mechanisms (masonry). Other mechanisms: this category includes those

mechanisms that could not directly be recognized as in plane or out of plane mechanisms, but which in-volve the building as a whole, generating the total col-lapse of the structure (i.e. detached floor and roof

beam, irregularity between adjacent structures, etc.). The local mechanisms are classified as follows.

Local dislocation: they are mechanisms, for exam-ple, that arise for arch or architrave failure, or in part of the structure characterized by different irregulari-ties, often connected to significant stiffness variations (i.e. inappropriate retrofitting such as reinforced con-crete interventions in masonry structures, etc.); the phenomenon generally determines the crumbling and the expulsion of the material in the areas adjacent to the element involved.

Elements causing horizontal thrust: these mecha-nisms are determined by the action of single elements that produce horizontal thrust on the supporting struc-tures; good examples are the thrusting elements of a roof or the vaults, the thrust action of which is not sufficiently balanced.

Therefore, with reference to the classification out-lined above, 16 different collapse mechanisms have been identified for masonry structures, which are re-lated to the seismic damage types. The collapse mechanisms for masonry structures are shown in Fig-ure 1 (global mechanisms) and Figure 2 (local mechanisms). The seismic damage has also been clas-sified in table form.

7.5 R.c. structures: damage mechanisms.

The global mechanisms are subdivided as follows. Strong beam-weak column: they occur in buildings

characterized by beams having high strength com-pared to columns with significant lower resistance; this causes the creation of plastic hinges in the col-umns (weaker elements) instead of the beams (stronger elements), with the subsequent concentra-tion of inelastic deformation in the columns; the mechanisms could involve all or several storeys, lead-ing to a “pancake type” collapse.

Weak beam-strong column: they occur in buildings characterized by beams having low strength against columns with appreciable higher resistance; the plas-tic hinges develop in the beams (weaker elements) and not in the columns (stronger elements), and there-fore inelastic deformation occurs in the beams; the mechanisms could occur for bending in the beams (more ductile elements), shear in the beams (less ductile elements) or detached reinforcement.

Weak joints: they occur when the structural frame is characterized by weak nodes compared to the ac-tions transferred by beams and columns; the mecha-nism starts with the creation of diagonal cracks in the joints leading to sliding between beam and col-umn; the collapse of a number of joints affects frame stability, causing the loss of the equilibrium and the subsequent collapse of the whole structure.

Weak storey: they occur in buildings with a storey which is less strong than the others, and with resis-tance characteristics significantly different at one level with respect to the other levels; it results as a

consequence of a lack of elements with adequate stiffness and strength (i.e. infill panels) against the horizontal actions; in these cases, seismic energy is mainly dissipated through that floor.

Foundation subsidence: these mechanisms occur when seismic actions involve the foundation level causing a vertical subsidence effect; in these cases the structures show diagonal cracks in the infill pan-els, horizontal misalignment in the beams and cracks at the ends, or increase in vertical cracks along the height of the building; in the case of frame structures of significant stiffness and when extensive subsi-dence is reported, a rigid rotation or sliding move-ment of the building can occur.

Figure 3. MEDEA: Global Collapse Mechanisms (r. concrete).

Figure 4. MEDEA: Local Collapse Mechanisms (r. concrete). The local mechanisms are classified as follows.

Due to structural elements: this category refers to those mechanisms caused by structural elements producing a localized action in a part of the struc-ture, such as the hammering between adjacent build-ings, the strut action at the ends of the column due to the infill panels, the floor collapse caused by large displacements at a joint/support; these circumstances are usually the result of structural deficiency.

Due to the infill panels or partitions: these mecha-nisms are similar to the ones occurring in masonry structures, related to the poor tensile strength of the material; they could produce in plane or out of plane ruptures.

Due to the roof collapse: these mechanisms occur due to the collapse of weak masonry walls support-ing the roof or as a result of the thrust effect of pitched roofs.

The collapse mechanisms for r.c. structures are shown in Figure 3 (global mechanisms) and Figure 4 (local mechanisms). The seismic damage has also

been classified in table form. In addition to the above, in the case of r.c. structures, wall collapse mechanisms are also classified, taking into account the differences among structural typologies: single walls (solid or with various openings), double walls, walls/frame.

7.6 The Damage Assessment

The damage tables provide a classification of the main damage types that may be encountered during a survey, for each single element (vertical structures, horizontal structures, stairs, non-structural ele-ments). Every damage type is described by a specific form containing notes, diagrams showing different damage levels following a predefined scale. The scope is to address the macro-seismic assessment and to provide a tool to assist the surveyor in the completion of the sections of the safety check relat-ing to the evaluation of the damage level of the structural component analysed. MEDEA provides a hypothesis of possible links to other damage types in the same elements examined or in those elements of the structure that could be recognized as compatible with respect to a specific collapse mechanism. The tool allows for the analysis of the structure through the association among the existing damage types and their recognition as congruent to a possible global structural behaviour (Papa et al. 2004). MEDEA al-lows for a seismic damage and mechanism correla-tion. The tool indicates the possible mechanisms congruent to the chosen damage. It also allows for the safety analysis, and to carry out the evaluation of the construction typology and associated vulnerabil-ity class, the damage level for elements and build-ing, the safety assessment of the building and poten-tial interventions. The MEDEA survey forms refer to the damage tables and the global and local col-lapse mechanisms tables. Separate forms refer to masonry structures and reinforced concrete struc-tures respectively. The MEDEA form includes vari-ous sections including the following: a section on the identification of the building; a section on vul-nerability parameters for the structure; and a matrix for the mechanisms and structural damage. In the case of masonry buildings, the matrix refers to the global and local mechanisms, and to the structural damage with respect to vertical and horizontal struc-tures. In the case of reinforced concrete structures, the matrix refers to the mechanisms which are clas-sified as; global, local and wall collapse mecha-nisms, and to the structural damage with respect to vertical structures, horizontal structures, panels and walls. The survey form allows for the collection of information regarding the collapse mechanisms on the damaged structure, and it is possible to make a hypothesis regarding the total collapse. A procedure was proposed, for the evaluation of the Safety Index IA, based on the analysis of the degree of develop-

ment of the prevalent mechanism in the building. Through this tool, the correlation between the Safety Index range and the global damage has been investi-gated (Papa et al. 2004).

During the Investigation carried out by the COST C26 team, the damage types were recorded in the structures assessed in the areas investigated, on the basis of detailed external and internal surveys. A scale of the intensity of damage was assigned, with a score from 1 to 3, according to the intensity of the observed damage recorded during the survey. De-tailed information was compiled, including photo-graphic surveys. The damage types recorded were linked to the associated collapse mechanisms in the matrix. In particular, the assessment included the re-view of damage types in masonry and reinforced concrete buildings (Kouris et al. 2010; Borg 2010).

8 THE EEFIT METHODOLOGY

The Earthquake Engineering and Field Investigation Team (EEFIT) organises field missions in the im-mediate aftermath of earthquakes in order to gather data on the performance of structures, foundations, services etc. EEFIT has been carrying out regular investigations of earthquake damage and following the Aquila earthquake a reconnaissance team visited the affected area over a period of 10 days (EEFIT 2009). The towns visited by EEFIT comprised: L’Aquila, Coppito, Scoppito, Onna, San Gregorio, Barisciano, Poggio Picenze, Fossa, Valle D’Ocra, Lucoli, Preturo, Cansatessa and San Demetrio ne’ Vestini. In each town visited building damage, infra-structure damage (e.g. damage to bridges and roads), damage to industrial plants and to historical build-ings were observed and reported. Furthermore, evi-dence of faulting and geotechnical failures were sought out. In order to collect this information, three main types of survey were employed by the EEFIT Team in the field: general observation; rapid survey using EMS-98; detailed survey.

General observation of damage and damage ex-tent were carried out in every location visited by the team. Rapid surveys were carried to quantify the proportion of different damage levels in selected streets. These consisted in noting down the structural type, height, size and damage state of each building along a road, from an external survey. Internal dam-age was not assessed. For this rapid survey the dam-age scales for reinforced concrete and masonry pre-sented in EMS-98 (Grünthal 1998) were used. EMS-98 presents graphical illustrations and descriptions of damage for different structure types in terms of 5 damage states. Figure 5 shows the damage scale for masonry buildings. The results of these assessments were used to estimate the EMS-98 intensity (Grün-thal 1998) in each city. These surveys were not

comprehensive macro-seismic surveys and were car-ried out in a small time window, sometimes for only part of the village/town visited, with the purpose of gaining an overall understanding of the extent of the affected area. For the purpose of the EMS-98 inten-sity survey, masonry residential buildings were as-sumed to be vulnerability Class B and reinforced concrete buildings vulnerability Class C, except for in locations of new buildings (post 2003) where re-inforced concrete buildings were assigned to vulner-ability Class D. The intensity survey for the loca-tions was carried out assigning an aggregated percentage of buildings to each damage state.

Figure 5: The EMS-98 damage scale for masonry buildings

Detailed surveys were instead carried out for

structures of particular interest. As the team was large, in order to get a consistent evaluation of dam-age, a survey sheet was drawn up for the detailed damage surveys. These sheets allow data to be col-lected on the structure: its lateral load resisting sys-tem, roof system, number of stories above and below ground, storey height, building material type and quality, occupancy type, approximate building age, approximate floor area, regularity in plan and eleva-tion. The sheet also records dimension of structural members. The overall damage state is recorded (as per EMS-98 damage scale), and there is space on the form for entering a more detailed description of the damage. Where the information is available (from say, owners) details of deaths and injuries in the building are collected. Furthermore, for each of

these surveys detailed photographs, measurements, and GPS coordinate readings were taken. The dam-age observed from the L’Aquila earthquake varied substantially depending on the location, building ty-pology, age of construction and condition. However, the EMS-98 intensity surveys show that there ap-pears to be more damage in the valley region of L’Aquila than over the sloping topography, and more damage east of Aquila compared to the west.

9 CONCLUSIONS

The seismic damage data, collected after an earth-quake, is related to actual building performance, and therefore recognised to be of great importance. The use of unambiguous and homogenous techniques is important in order to guarantee an objective evalua-tion.

The assessments are required for the protection of human life and property by identifying buildings prone to collapse during after shocks, and problems in transportation routes. The assessments are also important for the estimation of temporary housing needs. Furthermore, damage assessment can provide data for future research studies and urban planning. Moreover, the post-earthquake data is important in order to prepare reasonable prevention plans, for ef-fective emergency management. The post-seismic damage assessment is considered to be an important step in establishing the reconstruction strategy.

10 REFERENCES

Borg R.P., 2010. Seismic Damage Assessment of Structures; L’Aquila Earthquake, April 2009. Seismicity and Earth-quake Engineering. L’Aquila Earthquake of April 2009. Eds. R.P. Borg, ISBN-978-99932-0-879-2, Kamra Tal-Periti, April 2010, Valletta, Malta.

COST, 2006. COST, European COoperation in the field of Sci-entific and Technical research, Transport and Urban Devel-opment, COST Action C26: “Urban Habitat Constructions Under Catastrophic Events”, 2006-2010.

EEFIT, 2009. The L’Aquila, Italy earthquake of 6 April 2009. A preliminary field report by EEFIT. Available at: www.eefit.org.uk.

Goretti A., Di Pasquale G., 2002. An Overview of Post-Earthquake Damage Assessment in Italy, EERI Interna-tional Workshop.

Grünthal G. (Ed.), 1998. European Macroseismic Scale 1998 (EMS-98). European Seismological Commission, subcom-mission on Engineering Seismology. Conseil de l’Europe, Cahiers du Centre Européen de Géodynamique et de Séi-smologie, 15, Luxembourg, 99 pp.

Indirli M., 2010. The 6th April 2009 L’Aquila earthquake: from ruins to reconstruction. Seismicity and Earthquake Engineering: L’Aquila Earthquake of April 2009. Eds. R.P. Borg, ISBN-978-99932-0-879-2, Kamra Tal-Periti, April 2010, Valletta, Malta.

INGV. http://portale.ingv.it/. Kouris L.A., Borg R.P, Indirli M., 2010. The L’Aquila Earth-

quake, April 6th, 2009: a review of seismic damage mecha-

nisms. Proceedings of COST Action C26 Final Interna-tional Conference on Urban habitat construction under catastrophic events, Naples, 16-18 September 2010.

Linee guida, 2006. Linee Guida per la valutazione e riduzione del rischio sismico del patrimonio culturale con riferimento alle norme tecniche per le costruzioni (Guidelines for eva-luation and mitigation of seismic risk to cultural heritage). Italian Ministry for Cultural heritage, July 2006.

MEDEA, 2005. Manuale di Esercitazioni sul Danno Ed Agibi-lità per edifici ordinari (User’s manual on damage and sa-fety for ordinary buildings). http://gndt.ingv.it/Att_scient/ Molise2002/ San_Giuliano/Strumenti%20di%20rilievo.pdf.

Papa F., Zuccaro G., 2004. MEDEA: A Multimedia and Didac-tic Handbook for Seismic Damage Evaluation, European Seismological Commission, Potsdam.

Protezione Civile, 2002. Manuale per la compilazione della scheda di 1° livello di rilevamento danno, pronto intervento e agibilità per edifici ordinari nell'emergenza post-sismica. Dipartimento della Protezione Civile, Servizio Sismico Na-zionale, Gruppo Nazionale per la Difesa dai Terremoti, 2002.

Protezione Civile 2010a. AeDES and AeDES Modified, Sche-da di 1° livello di rilevamento danno, pronto intervento e agibilità per edifici ordinari nell’ emergenza post-sismica, First Level form for safety assessment, damage investiga-tion, prompt intervention for ordinary buildings in the post-earthquake emergency, http://www.protezionecivile.it/cms/ attach/editor/schedadanni.pdf.

Protezione Civile 2010b. Scheda per il rilievo del danno ai Be-ni Culturali: chiese (Form for the damage survey to cultu-ral heritage: churches), http://www.protezionecivile.it/cms/ attach/editor/MOD_A-DC_SCHEDA_DANNO_CHIESE_ 2006.pdf.

Protezione Civile 2010c. Scheda per il rilievo del danno ai Be-ni Culturali: palazzi (Form for the damage survey to cultu-ral heritage: buildings), http://www.protezionecivile.it/cms/ attach/editor/MOD_B_DP_SCHEDA_DANNO_ PALAZ-ZI_ 2006.pdf.

USGS. http://www.usgs.gov/.