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A complete research of seismic risk assessment is presented herein focused on the existing build- ings of the extended urban region of Athens in Greece. The seismic risk assessment is fulfilled by discriminating the current study in two approaches, probable and actual, conducting afterwards between them a comparison analysis. In the first part, a pilot methodology is developed for the seismic loss assessment in monetary terms regarding the buildings damages, consistent with the National Programme for Earthquake Management of Existing Buildings (NPEMEB). The building stock consists of typical building types of Southern Europe and refers to 750,085 buildings (18.80% of buildings in Greece) situated in the entire region of Athens according to the results of the 2000-1 statistical census. A wider research of seismic risk assessment could include direct losses of infrastructures and indirect economic losses. The evaluation of loss due to building damage in a certain region requires an assessment of both seismic hazard and vulnerability of the building stock in the study area. Four different existing damage scenarios are applied for the vulnerability assessment. The results of the seismic risk assessment for the four different aspects of the es- timated damage and the different soil conditions are presented in a map of the study region. The existing vulnerability curves corresponding to defined types of buildings have been derived from the National Technical Chamber of Greece and also from recently developed DPMs. The last DPMs were obtained in a previous research (Eleftheriadou, 2009) from the process of a created damage database after the 7th of September 1999 Parnitha’s earthquake and comprised 180,945 buildings which developed damage of varying degree, type and extent. In the second part of the research, the seismic risk is evaluated from the available data regarding the mean statistical repair/ strengthening or replacement cost for the total number of damaged structures (180,427 buildings) after the same (1999 Parnitha’s) seismic event. Data regarding the compatible (budget approved according to the ministry’s provisions) repair cost has been collected. The structural losses in monetary terms for the 180,427 buildings damaged structures are evaluated equal to 2450.0 Μ� 1887.8 Μ�and 2118.9 Μ�based on the previously mentioned statistical seismic risk data. The statistically derived repair cost for Attica is compared with the results of the economic loss esti- mation for buildings using the aforementioned risk assessment methodology. From the analysis results, the seismic scenario based on the recently developed DPMs (Eleftheriadou, 2009) pre- sented the better correlation (2627.77 M� with the total statistically evaluated repair cost (2450.02 M�. It is important to stress that the inclusion of the coefficient parameter S overes- timates significantly the seismic losses. The last result should be taken into consideration in future risk researches. The comparison of the estimated economic loss with the statistical repair cost calibrates the reliability of the commonly used risk assessment method and serves in the im- provement of seismic security prioritizing the criteria for seismic rehabilitation programmes of existing buildings.

The devastating impacts of seismic events during the last decades in areas with densely concentrated population and buildings pointed out that these environments are highly exposed to human and economic losses. In risk analysis the probability of losses is calculated over a specified period of time due to all the possible future seis- mic events, whereas in a seismic scenario the impact of a given earthquake is investigated and quantified. Reli- able earthquake loss estimation (in monetary terms) for buildings struck by an earthquake is of growing impor- tance both for the planning of appropriate and cost effective earthquake mitigation measures and for insurance purposes, and also for the definition of criteria for prioritizing seismic strengthening (rehabilitation) programmes for existing buildings. Decisions regarding the seismic rehabilitation of existing buildings require both engi- neering and economic studies and consideration of social priorities. Pre- and post-earthquake upgrading of a city’s existing building stock is one of the most conflictual and difficult issues of public policy decisions.

The interest in earthquake management by governments and policies is obvious considering the numerous projects financed for this purpose. After the socio-economic impact of the earthquakes in Turkey (Izmit on 17^{th}-8-1999 & Düzce on 12^{th}-11-1999), and Greece (Athens on 7^{th}-9-1999), the European Commission funded in 1999 the RISK-UE project: “An advanced approach to earthquake risk scenarios with application to different European towns”, aiming at the assessment of seismic risk in European urban centres. Seven research centres from European countries (France, Italy, Romania, Spain, Greece, FYROM, and Bulgaria) were involved in the project. Shortly before RISK-UE, another international project, RADIUS (Risk Assessment Tools for Diagnosis of Urban Areas against Seismic Disasters) aimed to develop earthquake damage scenarios in urban areas of nine case-study cities all over the world. The ENSeRVES project (European Network on Seismic Risk, Vulnerability and Earthquake Scenarios) in 1997 gathered together teams of scientists of different categories (seismologists, geologists, engineers, architects, etc.) involving 11 international institutions working on earthquake engineering and seismology. Along similar lines, the National Technical Chamber of Greece (NTCG) with the cooperation of Greek universities provided in 1996 funding to the Earthquake Planning and Protection Organization (EPPO) for carrying out the “National Programme for Earthquake Management of Existing Buildings” [

The evaluation of loss due to building damage in an area struck by an earthquake depends both on seismic hazard and the vulnerability of the building inventory in the certain region. Loss is defined as the human and financial consequences of damage, including injuries or deaths or the costs of repair. A wider research of seis- mic risk assessment could include direct economic losses (

Based on a quantitative assessment of seismic vulnerability, the probability of damage to given building types caused by earthquakes of various intensities can be predicted [

It is important to clarify the distinction between risk and vulnerability. Risk combines the expected losses from all levels of hazard severity, also taking their occurrence probability into account, while vulnerability of an element is usually expressed for a given hazard severity level. Components of seismic risk assessment and loss estimation are 1) Hazard analysis; 2) Local site effects (microzonation); 3) Exposure information (structural in- ventory); 4) Vulnerability analysis; 5) Estimation of risk and loss. Since the standard definition of risk is a pro- bability or likelihood of loss, between zero and one, it may be more appropriate to express risk as Risk = Hazard × Vulnerability while loss depends on the value of the exposure at risk, given by Loss = Hazard × Vulnerability × Exposure. Thus, while seismic hazard is a product of natural processes, seismic risk and loss are dependent on the vulnerability and social exposure in terms of the built environment, human population, and value of opera- tions.

The first step for the development of any earthquake scenario is the assessment of damage in structures. Sev- eral methodologies and relations exist attempting to express damage indices in economic loss. The correlation of structural damage to economic loss is indispensable for the estimation of seismic risk [

The research includes a study for the seismic vulnerability and risk assessment in the extended region of Ath- ens (Greece) struck by the 7^{th}-9-1999 Parnitha’s earthquake. The building stock in the study area consists of typical building types, representative of the materials, seismic codes and construction techniques of Southern Europe. The building exposure refers to 750,085 buildings which are situated in 122 regions of Attica according to the results of the 2000 statistical census (one year after the seismic event), information obtained from the Na- tional Statistics Service of Greece (NSSG). For the evaluation of seismic hazard, data specific to the characteris- tics of the earthquake that struck the area has been used. The seismic demand is characterized by the ratio, _{ }is the PGA by which each municipality of Attica is characterized according to the hazard map of the 2003 Seismic Code [

ability curves have been derived from a hybrid approach, which combines statistical data with appropriately processed results from nonlinear dynamic or static analyses, that permit extrapolation of statistical data to PGA’s and/or spectral displacements for which no data are available. The forth damage scenario is based on relatively recently developed Damage Probability Matrices-DPMs [^{th} of September 1999 Parnitha’s earthquake. The empirical vulnerability assessment is generally based on the distribution of damage reported in post-earthquake surveys and treats these data according to statistical procedures. It includes the real response of the exposed building stock, taking into account all the structural characteristics, topography, site and soil conditions of Greece. Sur- vey data can rarely provide a complete set of data. The difficulty focuses on the lack of a sufficiently large set of reliable empirical data, due to the limited number of damaging earthquakes at a small distance from densely populated areas, covering a wide range of ground motions [

Information regarding the compatible (budget approved according to the ministry’s provisions) repair cost af- ter the 1999 Parnitha’s earthquake has been used in order to conduct correlation analysis with the estimated losses. The statistically derived repair cost for the area is compared^{ }with the results of the economic loss estima- tion obtained using the pre-described procedure for the risk assessment. The comparison of the estimated eco- nomic loss with the compatible repair cost calibrates the reliability of the commonly used method for the risk assessment and serves in the improvement of seismic security and prioritizing the criteria for seismic rehabilita- tion programmes of existing buildings.

The development of seismic vulnerability and risk models needs a classification system to characterize the earthquake-exposed building stock and describe its damage. A complete set of data (i.e. covering the entire city) is able to be provided only by the National Statistics Service of Greece (NSSG). The current research is focused on the seismic risk assessment of Attica area struck by the 7^{th}-9-1999 Parnitha’s earthquake and refers to 750,085 buildings which are located in 122 regions. The above information has been derived from NSSG ac- cording to the information of 2000-1 census of buildings, conducting just a year after the occurrence of the earthquake. According to the same source, the building exposure in Attica represents the 18.8% (/3990970) of total population of the entire building stock in Greece (total number of buildings). A full set of data collected from NSSG regarding: 1) The total number of buildings of the study area (Attica); 2) The number of buildings categorized according to the construction materials (reinforced concrete, masonry, metal or wood or stone or other); 3) The number of buildings categorized according to the construction materials combined with the year of construction (Seismic Code); 4) The number of buildings categorized according to the construction materials and the period of construction combined with the height (number of floors). The classification system should also take into account the building types of the existing vulnerability models. The level of seismic design and construction detailing, could generally be discriminated in four subclasses, as follows: a) Without Seismic Code (or pre-seismic code: year of construction before 1959): RC buildings with practical very low level of seismic design or no seismic design, and poor quality of detailing; b) Low Seismic Code (the 1^{st} Greek Seismic Code of 1959: year of construction 1959-1985): RC buildings with low level of seismic design (corresponding approxi- mately to pre-1980 codes in Southern Europe); c) Moderate Seismic Code (the 1^{st} Greek Seismic Code of 1959 plus the 1985 Supplement Clauses: year of construction between 1985-1995): R/C buildings with medium level of seismic design (corresponding approximately to post-1980 codes in S. Europe) and reasonable seismic de- tailing of R/C members; d) High Seismic Code (new Greek generation of RC and seismic codes similar to Eurocodes: year of construction after 1995): R/C buildings with adequate level of seismic design according to the new generation of seismic codes and ductile seismic detailing of R/C members including sufficient descrip- tions for detailing and anchorage. Useful information about the building exposure of Attica, which represents a reliable sample of Greece and generally South Europe, after elaborating the initial data collected from NSSG. The analysis results are presented in Tables 1-3 including the building stock regarding construction materials, period of construction connected to the seismic codes and number of floors.

Information that was missing for the needs of the research was derived from previous studies (Xanthi, 2005; 2007; Tripoli, 2004; Corfu, 2005) of the National Programme for Earthquake Management of Existing Buildings. Thus, buildings of Attica with 3 to 5 floors are distributed as follows: 1) RC buildings designed and constructed

Structural System | Reinforced Concrete | Bricks/Cinder Blocks | Metal | Wood | Stone | Other | Non Declared | Total |
---|---|---|---|---|---|---|---|---|

Number of Buildings | 565,583 | 117,481 | 7268 | 4226 | 43,284 | 10,957 | 1286 | 750,085 |

Percentage (%) | 75.4 | 15.6 | 1.0 | 0.6 | 5.8 | 1.4 | 0.2 | 100.00 |

Period of Construction (Seismic Code, SC) | All Buildings | RC Buildings | Other: Masonry, Metal, Wood, Stone, Other, Non Declared | |||
---|---|---|---|---|---|---|

Number of Buildings | Percentage (%) | Number of Buildings | Percentage (%) | Number of Buildings | Percentage (%) | |

Earlier than 1985 | 578,635 | 77.1 | 420,096 | 74.3 | 158,539 | 85.9 |

1985-1995 | 114,632 | 15.3 | 98,208 | 17.3 | 16,424 | 8.9 |

After 1995 | 56,818 | 7.6 | 47,279 | 8.4 | 9539 | 5.2 |

Total | 750,085 | 100.00 | 565,583 | 100.00 | 184,502 | 100.00 |

Number of Floors | All Buildings | RC Buildings | Other: Masonry, Metal, Wood, Stone, Other, Non Declared | |||
---|---|---|---|---|---|---|

Number of Buildings | Percentage (%) | Number of Buildings | Percentage (%) | Number of Buildings | Percentage (%) | |

1 Floor | 332,619 | 44.3 | 180,669 | 31.9 | 151,950 | 82.36 |

2 Floors | 204,444 | 27.3 | 177,350 | 31.4 | 27,094 | 14.68 |

3 - 5 Floors | 182,927 | 24.4 | 177,622 | 31.4 | 5305 | 2.88 |

≤6 Floors | 30,095 | 4.0 | 29,942 | 5.3 | 153 | 0.08 |

Total | 750,085 | 100.00 | 565,583 | 100.00 | 184,502 | 100.00 |

earlier than 1985: 47.0% with 3 floors, 38.6% with 4 floors and 14.4% with 5 floors; 2) RC buildings designed and constructed between 1985 - 1995: 39.1% with 3 floors, 27.6% with 4 floors and 33.3% with 5 floors; 3) RC buildings designed and constructed after 1995: 54.5% with 3 floors, 25.5% with 4 floors and 20.0% with 5 floors; 4) masonry buildings are considered with 3 floors. In the category of six and more floors all buildings are considered having six floors. As far as RC buildings of Attica with ground floor without infill panels (pilotis) are regarded: a) 24.9% buildings designed and constructed earlier than 1985; b) 57.9% buildings designed and constructed between the period 1985 - 1995; and c) 59.7% buildings after 1995. Finally, the distribution of the mean constructed area per floor based on the previous studies has occurred: a) 150 m ^{2} for buildings of RC structural system designed and constructed earlier than 1985; b) 133 m ^{2} for RC buildings designed and constructed be- tween the period 1985 - 1995; c) 180 m ^{2} for buildings of reinforced concrete structural system after 1995; and d) 74 m ^{2} for masonry buildings.

Four different damage scenarios according to existing vulnerability curves are considered for the seismic risk assessment. These vulnerability models (in form of curves or DPMs) regarding typical structural types have been proposed by National Technical Chamber of Greece in 2006 (7 structural building types in 3 different damage scenarios) and also by Eleftheriadou [^{th} of September 1999 Parnitha’s earthquake. The database comprises 180,945 buildings which developed damage of varying degree, type and extent [

The Median Damage Factors (%) for the four different damage scenarios MDFij (%):

Parnitha’s near field earthquake ^{th} of September, 1999 occurred at a small epicentral dis- tance ( 18 km ) from the historical centre of the city of Athens in Greece, a densely populated area and it is con- sidered the biggest recent natural disaster in Greece regarding the monetary loss. The parameter that characte- rizes the seismic input, in National Technical Chamber of Greece [

The examined building stock (750,085 buildings) refers to 122 regions of Attica. Among them, 80 belong in seismic zone I according to the Greek Seismic Code with equivalent ground acceleration

Structural Types (ST) | Design Seismic Code Period (Seismic Code) | MDFi1 (%) | MDFi2 (%) | MDFi3 (%) | MDFi4 (%) | ||
---|---|---|---|---|---|---|---|

RC with infills in ground floor (normal) | 1 | 1 | Earlier than 1985 | 6.00 | 5.20 | 7.90 | 4.56 |

RC without infills in ground floor (pilotis) | 4 | 7.20 | 6.24 | 9.48 | |||

RC with infills in ground floor (normal) | 2 | 2 | 1986-1995 | 2.50 | 2.00 | 3.33 | 2.26 |

RC without infills in ground floor (pilotis) | 5 | 3.00 | 2.40 | 4.00 | |||

RC with infills in ground floor (normal) | 3 | 3 | After 1995 | 1.10 | 1.30 | 3.33 | 1.42 |

RC without infills in ground floor (pilotis) | 6 | 1.10 | 1.30 | 3.33 | |||

Masonry of bricks | 7 | 4 | All periods | 19.40 | 12.50 | 15.90 | 10.56 |

Structural system of stone, wood, metal or other | 5 | 9.99 |

Number of Studied Municipalities | Macroseismic Intensity I | a_{g} (cm/sec^{2}) | a_{o} (cm/sec^{2}) | a_{g}/a_{ο} |
---|---|---|---|---|

1 - 3 | IX | 804.32 | 235.44 | 3.42 |

4 - 5 | VIII | 383.75 | 156.96 | 2.44 |

6 - 13 | VIII | 383.75 | 235.44 | 1.63 |

14 - 31 | VII | 183.09 | 156.96 | 1.17 |

32 | VII+ | 265.07 | 235.44 | 1.13 |

33 - 36 | VI+ | 126.47 | 156.96 | 0.81 |

37 - 40 | VII | 183.09 | 235.44 | 0.78 |

41 - 50 | VI | 87.36 | 156.96 | 0.56 |

51 - 65 | V+ | 60.34 | 156.96 | 0.38 |

66 - 69 | VI | 87.36 | 235.44 | 0.37 |

70 - 98 | V | 41.68 | 156.96 | 0.27 |

99 - 109 | V+ | 60.34 | 235.44 | 0.26 |

110 - 118 | V | 41.68 | 235.44 | 0.18 |

119 - 120 | IV | 19.89 | 156.96 | 0.13 |

121 | IV | 19.89 | 235.44 | 0.08 |

122 | III | 9.49 | 235.44 | 0.04 |

Estimated macroseismic intensity values according to the Modified Mercalli Scale: 1) Geodynamic Institute of the National Observatory of Athens [

the ratio

According to the National Technical Chamber of Greece [^{st} Seismic Code of 1959 standing up to 1985 or the 1^{st} Seismic Code of 1959 plus the 1985 Supplement Clauses (1985-1995), with different from today’s design seismic code, a relative coefficient

Summarizing, two different scenarios for soil conditions (a = good soil conditions-smaller PGAs and b = me- dium soil conditions-bigger PGAs) and four damage scenarios have been applied in the applied methodology for seismic risk estimation. An alternative scenario for

Seismic design acceleration | |||||
---|---|---|---|---|---|

Zone I, Soil | 0.070 | 2.286 | 2.763 | 3.429 | 5.014 |

Zone I, Soil | 0.105 | 1.524 | 1.707 | 2.286 | 2.763 |

Zone IΙ, Soil | 0.105 | 1.524 | 1.707 | 2.286 | 2.763 |

Zone IΙ, Soil | 0.140 | 1.143 | 1.193 | 1.714 | 1.964 |

Zone IΙΙ, Soil | 0.140 | - | - | 1.714 | 1.964 |

Zone IΙΙ, Soil | 0.210 | - | - | 1.143 | 1.193 |

SC 1995 (1995-2003) | 0.120 | 1.333 | 1.450 | - | - |

SC 1995 (1995-2003) | 0.160 | 1.000 | 1.000 | 1.500 | 1.675 |

100%) the upper limit of the vulnerability curve (MDF for

A pilot methodology is presented herein for the seismic loss assessment in monetary terms in Attica according to the National Programme for Earthquake Management of Existing Buildings [^{th} damage scenario (

The seismic loss factor (in monetary terms) is calculated according to the economic Mean Damage Factor % ^{2}).

^{2});

^{2}).

The seismic loss factors, and therefore the estimation of seismic risk, are calculated for every structural type regarding the entire studied area of Attica. The seismic risk loss factors for the four damage scenarios

The normalized seismic risk ratio _{4} divided to the total area of the building stock^{2} . Finally, the seismic loss estimation (in monetary terms) is estimated from the replacement cost

It is important to clarify that the estimated monetary loss does not include indirect loss (casualties, injuries, interruption of jobs etc.).

Information regarding the compatible repair cost after the 1999 Athens earthquake has also been collected. The statistically derived repair cost for the area is compared^{ }with the results of the economic loss estimation ob- tained using the pre-described procedure for the risk assessment. The comparison of the estimated with the compatible cost calibrates the reliability of the commonly used method for the risk assessment and would serve in subsequent earthquake loss estimation studies. The reliable seismic risk management is of crucial importance for the improvement of seismic security and sets the criteria for prioritizing seismic rehabilitation programmes for existing buildings.

The application of the aforementioned methodology requires the distribution of Attica building stock (750,085 buildings) selected from the National Statistics Service of Greece according to the statistical census 2000 in dis- tinct severity levels of seismic input, expressed by the ratio

The results of seismic risk assessment are presented in ^{2}, for all different damage scenarios that have been above explained. In

Note that, the inclusion of the coefficient parameter ^{st} (Volos) and 2^{nd} (ITSAK-AUTH) damage scenarios are close, the 3^{rd} (ARISTION) differs overestimating seismic risk while the 4^{th} [

The statistically derived compatible repair/strengthening or replacement cost has been calculated for the affected area and afterwards it is compared^{ }with the results of the economic loss estimation obtained from the application of the pre-described methodology for the risk assessment. It is important to clarify that the estimated monetary loss does not include indirect losses (casualties, injuries, loss of machines/furniture, stop of functions, etc.). The analytical estimation of the statistical repair cost needed the discrimination of damaged buildings from

Estimated seismic risk loss factors for entire Attica (750,085 buildings, 1,599,315 floors, 222,748,853 m^{2} area) according to Parnitha’s eathquake (7^{th}-9-1999) and the hazard map of Greek Seismic Code 2003 | ||||||
---|---|---|---|---|---|---|

Attica (122 regions) | a_{g} | Modification damage factor S | R_{m} = (m^{2}) | R_{4} (m^{2}) | r_{4} (%) | |

750,085 buildings according to statistical census 2000-1 | a_{g} estimated from 7^{th}-9-1999 Athens earthquake | S for soil type a | 33,098,617 | 24,582,219 | 11.0% | |

S for soil type b | 21,841,915 | 16,164,409 | 7.3% | |||

S = 1 | 12,480,507 | 8,847,700 | 4.0% | |||

a_{g} according to Seismic Code (a_{g}/a_{o} = 1) | S for soil type a | 43,309,677 | 29,569,852 | 13.3% | ||

S for soil type b | 26,535,299 | 18,141,327 | 8.1% | |||

S = 1 | 14,110,820 | 9,654,192 | 4.3% |

Parnitha’s earthquake in groups per damage level. Damage data include 178,578 buildings (^{th}-9-1999 Parnitha’s earthquake) with the one used for the simulation of ground motion in the methodology for the predicted losses.

The statistical compatible repair cost was based on two previous researches regarding damaged buildings after the 7^{th}-9-1999 Parnitha’s earthquake in the region of 1) Aharnes [

Macroseismic Intensity | |||||||
---|---|---|---|---|---|---|---|

Damage Level | Structural Type | V, V+ | VI, VI+ | VII, VII+ | VIII | IX | |

Light | RC1-MIX1 | 7030 | 5380 | 53,929 | 9413 | 5826 | 81,578 |

RC2-MIX2 | 385 | 571 | 3488 | 1719 | 2747 | 8910 | |

RC3-MIX3 | 165 | 78 | 1267 | 818 | 1322 | 3650 | |

MAS | 1366 | 1189 | 8463 | 2056 | 2157 | 15,231 | |

OTH | 164 | 245 | 1672 | 229 | 1008 | 3318 | |

Moderate | RC1-MIX1 | 2147 | 2213 | 21,059 | 4916 | 5784 | 36,119 |

RC2-MIX2 | 107 | 230 | 1428 | 577 | 1994 | 4336 | |

RC3-MIX3 | 8 | 41 | 264 | 202 | 702 | 1217 | |

MAS | 1074 | 988 | 6337 | 1340 | 1825 | 11,564 | |

OTH | 255 | 277 | 2339 | 322 | 770 | 3963 | |

Extensive | RC1-MIX1 | 107 | 125 | 878 | 271 | 563 | 1944 |

RC2-MIX2 | 2 | 3 | 176 | 27 | 191 | 399 | |

RC3-MIX3 | 1 | 3 | 13 | 3 | 66 | 86 | |

MAS | 90 | 134 | 766 | 184 | 536 | 1710 | |

OTH | 70 | 68 | 785 | 140 | 785 | 1848 | |

Collapse | RC1-MIX1 | 18 | 29 | 478 | 210 | 348 | 1083 |

RC2-MIX2 | 2 | 1 | 29 | 16 | 66 | 114 | |

RC3-MIX3 | 0 | 0 | 3 | 10 | 18 | 31 | |

MAS | 12 | 34 | 415 | 157 | 119 | 737 | |

OTH | 10 | 25 | 334 | 109 | 262 | 740 | |

TOTAL | 13,013 | 11,634 | 104,123 | 22,719 | 27,089 | 178,578 | |

NSSG | 284,164 | 104,764 | 277,137 | 41,676 | 32,574 | 740,315 |

Damage level | Building number | Mean area per building (m^{2}) | Mean compatible repair cost (€/m^{2}) | Total repair cost (M€) | Equivalent replacement area R (km^{2}) |
---|---|---|---|---|---|

Light (Green) | 112,687 | 247 | 33 | 918.51 | 3.09 |

Moderate (Yellow) | 57,199 | 285 | 62 | 1010.71 | 3.41 |

Extensive (Red) | 5987 | 190 | 297 | 337.85 | 1.14 |

Collapse | 2705 | 190 | 297 | 152.64 | 0.51 |

Total | 178,578 | 2419.71 | 8.15 |

Damage level | Building number | Mean area per building (m^{2}) | Mean compatible repair cost (€/m^{2}) | Total repair cost (M€) | Equivalent replacement area R (km^{2}) |
---|---|---|---|---|---|

Light (Green) | 112,687 | 148 | 35 | 583.72 | 1.62 |

Moderate (Yellow) | 57,199 | 177 | 92 | 931.43 | 2.58 |

Extensive (Red) | 5987 | 113 | 361 | 244.23 | 0.68 |

Collapse | 2705 | 113 | 361 | 110.35 | 0.31 |

Total | 178,578 | 1869.72 | 5.18 |

Damage level | Building number | Mean area per building (m^{2}) | Mean compatible repair cost (€/m^{2}) | Total repair cost (M€) | Equivalent replacement area R (km^{2}) |
---|---|---|---|---|---|

Light (Green) | 112,687 | 159 | 35 | 627.10 | 2.06 |

Moderate (Yellow) | 57,199 | 266 | 66 | 1004.19 | 3.29 |

Extensive (Red) | 5987 | 175 | 305 | 319.56 | 1.05 |

Collapse | 2705 | 175 | 305 | 144.38 | 0.47 |

Total | 178,578 | 0 | 0 | 2095.22 | 6.87 |

Damage level | Studies (1) + (2) | Number of buildings | Area (m^{2}) | Total repair cost (Μ€) | Mean repair cost (€/m^{2}) | Mean area (m^{2}/building) |
---|---|---|---|---|---|---|

Light (Green) | (1) | 51 | 12,610 | 0.414 | 33 | 247 |

(2) | 403 | 59,547 | 2.114 | 35 | 148 | |

(1) + (2) | 454 | 72,157 | 2.528 | 35 | 159 | |

Moderate (Yellow) | (1) | 1586 | 452,658 | 28.190 | 62 | 285 |

(2) | 350 | 61,871 | 5.717 | 92 | 177 | |

(1) + (2) | 1936 | 514,529 | 33.907 | 66 | 266 | |

Extensive (Red) | (1) | 919 | 174,906 | 51.904 | 297 | 190 |

(2) | 230 | 25,974 | 9.379 | 361 | 113 | |

(1) + (2) | 1149 | 200,880 | 61.284 | 305 | 175 | |

Total | (1) | 2556 | 640,174 | 80.509 | ||

(2) | 983 | 147,392 | 17.210 | |||

(1) + (2) | 3539 | 787,566 | 97.719 |

According to research (1) of Aharnes the damage data included 2556 buildings with 640,174 (m^{2}) total area and total repair cost 80.50 (M?. Among these buildings: 1) 51 developed minor (green) damages with 12,610 (m^{2}) total area and 0.41 (M? approved total repair cost; 2) 1586 developed moderate (yellow) damages with 452,658 (m^{2}) total area and approved total repair cost 28.19 (M?; 3) 919 developed extensive (red) damages with 174,906 (m^{2}) total area and 51.90 (M? approved total repair cost. According to research (2) of Ano Liosia the damage data included 983 buildings with total area repair 147,392 (m^{2}) and total repair cost 17.21 (M?. Among these buildings: a) 403 developed minor (green) damages with 59,547 (m^{2}) total area and approved total repair cost 2.11 (M?; b) 350 developed moderate (yellow) damages with 61,871 (m^{2}) total area and approved total repair cost 5.726 (M?; c) 230 developed extensive (red) damages with 25,974 (m^{2}) total area and approved total repair cost 9.38 (M?.

Based on the statistical data of Aharnes the total compatible repair cost has been evaluated equal to 2419.71 M? with equivalent replacement area of buildings 8.15 km^{2} (^{2} (^{2}.

The statistical costs for each damage category are presented in ^{2}, 361 ?m^{2} or 305 ?m^{2}, taking into consideration the two researches and the mean value, respectively. The last values have been adopted for the evaluation of the equi- valent replacement area ^{2}) from the total repair/strengthening cost per discrete damage levels in Tables 9-11. The evaluation and distribution of the statistical repair cost per intensity and damage level is presented in

Note that the approved budget by the National Agency for the Relief of Earthquake Victims for repair/replace- ment cost was based on a compatible work invoice. One third (1/3) of the approved budget was national assis- tance and the rest (2/3) was provided as without interest loan in earthquake victims. The upper limits that were set by the National Agency for the Relief of Earthquake Victims for the replacement and repair cost for habitat use regarding a building with area up to 120 m^{2} were 382 ?m^{2} and 191 ?m^{2}, respectively. The mean actual re- placement cost in the same period was 528 ?m^{2} according to estimations of the National Technical Chamber of Greece. Thus the reduction of the compatible to the actual cost could be attained by multiplying the first with the values of 1.78 (528/297 ?m^{2}), 1.46 (528/361 ?m^{2}) and 1.73 (528/305 ?m^{2}), regarding the 1) Aharnes research, 2) Ano Liosia and both (1 + 2) researches, respectively.

Finally, the created damage database referred in 180,945 buildings. Among them the 180,427 had the charac- terization of damage and the 178,578 were also able to be discriminated in structural types. Following the same assumptions an additional assessment of the compatible and the actual repair cost was fulfilled by multiplying with the values of 1.78, 1.46 and 1.73, as it is presented in Tables 14-16, regarding the Aharnes research, Ano Liosia and both (1 + 2) researches, respectively.

The results of seismic risk assessment are presented in

Damage level | Total repair cost (M€) V, V+ | Total repair cost (M€) VI, VI+ | Total repair cost (M€) VII, VII+ | Total repair cost (M€) VIII | Total repair cost (M€) IX | TOTAL (M€) |
---|---|---|---|---|---|---|

Light (Green) | 50.70 | 41.53 | 382.98 | 79.218 | 72.679 | 627.104 |

Moderate (Yellow) | 63.04 | 65.82 | 551.73 | 129.159 | 194.433 | 1004.185 |

Extensive (Red) | 14.41 | 17.77 | 139.74 | 33.359 | 114.276 | 319.556 |

Collapse | 2.24 | 4.75 | 67.20 | 26.794 | 43.394 | 144.379 |

TOTAL | 130.39 | 129.87 | 1141.65 | 268.53 | 424.782 | 2095.224 |

6.22% | 6.20% | 54.49% | 12.82% | 20.27% | 100.00% |

Damage level | Building number | Mean area per building (m^{2}) | Mean compatible repair cost (€/m^{2}) | Total repair cost (M€) | Equivalent replacement area R (km^{2}) | Actual repair cost (M€) |
---|---|---|---|---|---|---|

Light (Green) | 114,755 | 247 | 33 | 935.37 | 3.15 | 1664.96 |

Moderate (Yellow) | 56,533 | 285 | 62 | 998.94 | 3.36 | 1778.11 |

Extensive (Red) | 6423 | 190 | 297 | 362.45 | 1.22 | 645.16 |

Collapse | 2716 | 190 | 297 | 153.26 | 0.52 | 272.81 |

Total | 180,427 | 2450.02 | 8.25 | 4361.04 |

Damage level | Building number | Mean area per building (m^{2}) | Mean compatible repair cost (€/m^{2}) | Total repair cost (M€) | Equivalent replacement area R (Km^{2}) | Actual repair cost (M€) |
---|---|---|---|---|---|---|

Light (Green) | 114,755 | 148 | 35 | 594.43 | 1.65 | 867.87 |

Moderate (Yellow) | 56,533 | 177 | 92 | 920.58 | 2.55 | 1344.05 |

Extensive (Red) | 6423 | 113 | 361 | 262.01 | 0.73 | 382.54 |

Collapse | 2716 | 113 | 361 | 110.79 | 0.31 | 161.76 |

Total | 180,427 | 1887.82 | 5.23 | 2756.22 |

Damage level | Building number | Mean area per building (m^{2}) | Mean compatible repair cost (€/m^{2}) | Total repair cost (M€) | Equivalent replacement area R (km^{2}) | Actual repair cost (M€) | |
---|---|---|---|---|---|---|---|

Light (Green) | 114,755 | 159 | 35 | 638.61 | 2.09 | 1104.80 | |

Moderate (Yellow) | 56,533 | 266 | 66 | 992.49 | 3.25 | 1717.01 | |

Extensive (Red) | 6423 | 175 | 305 | 342.83 | 1.12 | 593.09 | |

Collapse | 2716 | 175 | 305 | 144.97 | 0.48 | 250.79 | |

Total | 180,427 | 2118.90 | 6.95 | 3665.70 | |||

Predicted seismic risk loss factors for entire Attica according to Parnitha’s eathquake (7^{th}-9-1999) (750,085 buildings, 1,599,315 floors, 222,748,853 m^{2} area) | |||||||||
---|---|---|---|---|---|---|---|---|---|

Attica (122 regions with 750,085 buildings) | a_{g} estimated from 7^{th}-9-1999 Parnitha’s earthquake | Modification damage factor S | 4 damage scenarios | Mean seismic risk factors of the 4 damage scenarios | Predicted repair cost Rc_{4} = R_{4}*c based on 1) Aharnes research 297 (€/m^{2}), 2) Ano Liosia research 361 (€/m^{2}), and the mean value (1) + (2) 305 (€/m^{2}) | ||||

R_{m} (Km^{2}) | R_{4} (Km^{2}) | r_{4} (%) | V_{4} (‰) | Rc_{4}^{(1)} (M€) | Rc_{4}^{(2)} (M€) | Rc_{4}^{(1)+(2)} (M€) | |||

S for soil type a | 33.10 | 24.58 | 11.0% | 37.0 | 7300.92 | 8874.18 | 7497.58 | ||

S for soil type b | 21.84 | 16.16 | 7.3% | 24.4 | 4800.83 | 5835.35 | 4930.14 | ||

S = 1 | 12.48 | 8.85 | 4.0% | 13.3 | 2627.77 | 3194.02 | 2698.55 | ||

Statistical economic losses including 180,427 damaged buildings (Tables 14-16) based on 1) Aharnes research, 2) Ano Liosia research, and 3) the mean value of (1) + (2) | |||||||||

1) Aharnes research | Equivalent replacement area R = 8.25 (km^{2}) | Compatible repair cost 2450.02 (M€) | |||||||

2) Ano Liosia research | Equivalent replacement area R = 5.23 (km^{2}) | Compatible repair cost 1887.82 (M€) | |||||||

3) Aharnes & Ano Liosia | Equivalent replacement area R = 6.95 (km^{2}) | Compatible repair cost 2118.9 (M€) |

compatible cost it is concluded that generally the seismic risk methodology overestimates seismic losses. As expected, the seismic scenario based on the developed DPMs [^{th}-9-1999 Athens damage data pre- sented the better correlation (2627.77 M? with the total statistically evaluated repair cost, especially when the last was based on Aharnes research (2450.02 M?. It is important to stress that the inclusion of the coefficient parameter

A complete research of seismic risk assessment is presented regarding the extended urban region of Athens in Greece. The seismic risk assessment is fulfilled by discriminating the current study in two approaches, probable and actual, conducting afterwards between them a comparison analysis. In the first part, a pilot methodology is developed for the seismic loss assessment in monetary terms regarding the buildings damages, consistent with the National Programme for Earthquake Management of Existing Buildings (NPEMEB). The building stock consists of typical building types of Southern Europe and refers to 750,085 buildings (18.80% of buildings in Greece) situated in the entire region of Athens according to the results of the 2000-1 statistical census. A wider research of seismic risk assessment could include direct losses of infrastructures and indirect economic losses. The evaluation of^{ }loss due to building damage in a certain region requires an assessment of^{ }both seismic hazard and vulnerability of the building^{ }stock in the study area. Three different scenarios for soil conditions (a, b and^{th} of September 1999 Parnitha’s earthquake and comprised 180,945 buildings which developed damage of varying degree, type and extent. The numerical values of the seismic risk factors (

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In the second part of the research, the seismic risk is evaluated from the available data regarding the mean sta- tistical repair/strengthening or replacement cost for the total number of damaged structures (180,427 buildings) after the same (1999 Parnitha’s) seismic event. Data regarding the compatible (budget approved according to the ministry’s provisions) repair cost has been collected. The structural losses in monetary terms for the 180,427 buildings damaged structures are evaluated equal to 2450.0 Μ? 1887.8 Μ?and 2118.9 Μ?based on the pre- viously mentioned statistical seismic risk data. The statistically derived repair cost for Attica is compared^{ }with the results of the economic loss estimation for buildings using the aforementioned risk assessment methodology. Conducting a comparison analysis between the estimated with the compatible repair cost it is concluded that generally the seismic risk methodology overestimates seismic losses. It should be mentioned, though, that the predicted loss takes into consideration the total building stock and not only the damaged buildings. From the analysis results, the seismic scenario based on the recently developed DPMs [