Estimating Losses from Future Earthquakes (1989) / Chapter Skim
Currently Skimming:
Pages 85-233
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 85... ...
Other ways of categorizing and analyzing earthquake loss estimation methods may be found in reviews of the field conducted from the 1930s to the present by Freeman (1932) , McClure (1973)
|
From page 86... ...
Cumulative set of Predicted Actual earthquake earthquakes to earthquake earthquake occur in time span , ~ , G EGG RAPH IC SCALE Local Regional/state National FIGURE A-1 Aspects of earthquake loss estimation studies. certainty, which reflects the inherent uncertainty in the field of earthquake loss estimation and is not necessarily indicative of methodological errors or weaknesses in any particular method.
|
From page 87... ...
H Wiggins of the earthquake problem as well as Company and to establish a basis for all other Engineering planning, prioritizing, users listed Geologists, and funding earthquake below Inc.1979; risk reduction efforts Algermissen et al., 1972 II: Hazard Guide hazard reduction Legislative, Alfors et al., reduction actions to reduce regulatory 1973; Ward, physical damage bodies; 1986; Office government of State officials Architect, and staffs; 1982; Los utilities and Angeles City corporations Planning Department, 1980 III: Emergency Facilitate more efficient Emergency Algerminsen planning emergency response response et al., 1972; agencies; D avis et al., utilities 1982a,b and corporations IV: Financial Rate earthquake risks of Insurance, Freeman, 1932; individual properties or mortgage California collective risk of lending, and Department of portfolios investment Insurance, industries 1985; Working Group Earth quake Hazard Reduction, 1978 V: Economic Estimate economic losses National Applied impact (including indirect, security Technology long-term economic agencies and Council, 1985 impacts)
|
From page 88... ...
The time variable is defined In terms of the cumulative losses estimated to occur in a given time span, in this case 197(}2000. The scope in terms of the kinds of facilities extends to all buildings, and both certainty and detail are relatively low.
|
From page 89... ...
earthquake · Cumulative set of Predicted Actual earthquakes to earthquake earthquake occur in time span l GEOGRAPHIC SCALE Local Regional/state · National FIGURE A-2 Aspects of a Type I, national-scale loss estimation study, using the example of J
|
From page 90... ...
TYPE II: HAZARD REDUCTION Type IT studies primarily support hazard reduction efforts, and the primary user is government agencies which adopt building codes regulating new construction or retroactive ordinances pertaining to existing hazardous facilities, land-use plans, and other laws and policies. Type ~ studies are often used for this purpose, but Type IT studies emphasize this hazard reduction purpose with more specific reference to the codes, ordinances, voluntary standards, or other concrete policy options under consideration, and limit their scope to the specific physical hazards, resources, or jurisdictions of interest.
|
From page 91... ...
91 Table of Contents PART A: ISOSEISMAL STUDIES. PART B: CASUALTIES AND DA\lAG E Section 1: Introduction Section 2: Bases for Analysi s Section 3: Effects on Local Medical Resources Major Hospitals Health Manpower.
|
From page 92... ...
. GEOGRAPHIC SCALE Local · Regional/state National FIGURE A-4 Aspects of a Type I, regional-scale loss estimation study, using the example of Algermmsen et al.
|
From page 93... ...
earthquake · Cumulative set of Predicted Actual earthquakes to earthquake earthquake occur in time span GEOGRAPHIC SCALE Local · Regional/state National E`IGURE A-5 Aspects of a Type II, state-scale loss estimation study, using the examples of Alfors et al.
|
From page 94... ...
Cumulative set of Predicted Actual earthquake earthquakes to earthquake earthquake occur in time span _ . GEOGRAPHIC SCALE I · Local Regional/state National FIGURE A-6 Aspects of a Type II, local-scale lose estimation study, using the example of Los Angeles City Planning Department (1980~.
|
From page 95... ...
Cumulative set of Predicted Actual earthquake earthquakes to earthquake earthquake occur in time span rim ~ GEOGRAPHIC SCALE Local · Regional/state National FIGURE A-7 Aspects of a Type III, regional-scale loss estimation study, using the examples of Davis et al.
|
From page 96... ...
This analysis pointed out the need to divide a financial sector, such as mortgage lending, into smaller categories when analyzing earthquake risk, because of the different characteristics in terms of assets, liabilities, income, and expenses of institutions such as commercial banks, savings and loans establishments, and life insurance companies. This type of study is an exception to the rule that financial risk studies generally focus on the monetary cost of damage as the type of loss of concern.
|
From page 97... ...
~ Cumulative set of Predicted Actual earthquake earthquakes to earthquake earthquake occur in time span GEOGRAPHIC SCALE Local · Regional/state National FIGURE A-8 Aspects of a Type IV, regional-scale loss estimation study, using the example of Freeman tl932~. Key: ~ = aspects that pertain to this type of study.
|
From page 98... ...
Cumulative set of Predicted Actual earthquake earthquakes to earthquake earthquake occur in time span GEOGRAPHIC SCALE l · Local · Regional/state ·National FIGURE A-9 Aspects of a Type V, regional-scale loss estimation study, using the example of FEMA Fedloss Method and its ATC-13 engineering component (Applied Technology Council, 1985~. Key: · = aspects that pertain to this type of study.
|
From page 99... ...
Widely accepted, easily applied, and objective ways of rating the certainty of loss estimate methods do not exist, and the issue of what constitutes acceptable certainty or acceptable detail can be decided only by reference to the fitness of the study for its intended purpose. This again brings up the important subject of the users and uses of loss estimation studies, a theme throughout this report.
|
From page 100... ...
Working Paper B User Needs IDENTIFICATION OF THE USER CO~IUNITY Early in the panel's deliberations it became clear that one of the most important considerations in exarn~ning the different methods of estimating earthquake losses would be the users' needs. This required defining who the users were so that their particular needs could be reflected in the panel's assessment of different loss estimation methods.
|
From page 101... ...
After extensive consultation with USGS, FEMA, and the COSMOS Corporation, consultant to the panel, a user was defined to be an appointed or elected public official who could be involved in developing data for use in loss estimation studies or in making decisions, based on those studies, which resulted in a lowered risk to the community. This definition, although limited, included officials in such functional positions as mayors, city managers, planners, directors of public works departments, building code officios, county commissioners and managers, and emergency service personnel at the local and state level.
|
From page 102... ...
The state list of users was overrepresented by emergency service managers. Finally, the list was overly representative of California users, which is not surprising given the fact that over a dozen loss studies have been conducted there.
|
From page 103... ...
The pane! was far more interested in the responses to the first questionnaire prior to participant exposure to the speakers, because of the focus on determining what state and local users (or potential users)
|
From page 104... ...
Participants indicated that too often the "experts" conducting the loss studies proceeded without regard to whether the users would understand what the results addressed or meant. In addition, some users indicated that the conflicts and disagreements among professional and technical experts had seriously undermined any efforts to utilize such studies.
|
From page 105... ...
Hence state participants wanted the loss studies to be for either states or regions, whereas local government officials desired a local focus. Local government participants used several examples of studies that were of such large geographic focus that they were of little value
|
From page 106... ...
Types of Formation m [ose Studies Loss studies have produced much information about projected losses for different types of structures serving various purposes. Participants at the workshop were asked to rank the importance of loss estimates to 19 different structures and facilities along a four-point ordinal scale from very important to not at all ~rnportant.
|
From page 107... ...
This desire for specificity is not surprising but may cause some difficulty because of the state of the art in loss estunates. Even more disturbing was the fact that of those state and local users at the workshop who had some familiarity with loss estimates, only 17 percent were very confident of the loss predictions.
|
From page 108... ...
Cost, Willingness, and Ability to Spend The issue of the willingness and ability to spend scarce fiscal resources on loss studies by the state and local user community has several important dimensions. First, the proposed sharing of costs between FEMA and state and local governments for other programs may in the near future include the monies used to finance loss studies.
|
From page 109... ...
As previously emphasized in this paper, participants strongly believed that to ensure the clarity and dissemination of study results for the largest possible user community, state and local representatives should be involved in the loss study process from its inception. CONCLUSIONS AND RECOMMENDATIONS The user needs subpane} concluded that some previous loss studies may not have sufficiently taken into account state and local users.
|
From page 110... ...
in the entire loss estimate study process. Loss estimation should and can be a vehicle of understanding the risk and potential losses from earthquakes.
|
From page 111... ...
State or regional loss studies must present sufficient information for local planning, preparedness, and mitigation activities. By compiling inventory data so that they can be d~saggregated and accessed by local units, producers win provide the opportunity for smaller units to use their studies.
|
From page 112... ...
More emphasis should be placed on the implications of the findings for set c planning and policy adoption. The loss study reports must be aimed at the audience of users and not other producers.
|
From page 113... ...
This paper describes earthquake hazards and how they can be quantified, reviews current practice in the specification of hazards for loss studies, and describes a range of hazard specifications that might be used ~ future loss studies. TYPES OF EARTHQUAKE HAZARDS The primary and most pervasive hazard associated with earthquakes is the shaking of the ground.
|
From page 114... ...
Collateral earthquake hazards caused by ground shaking include seiches, liquefaction, and landslides. These hazards can lead to complete destruction of structures.
|
From page 115... ...
is combined with seisrn~c hazard studies locally undertaken by state or local government geological agencies or local geotechnical consultants. Earthquake hazards and other inputs to loss estimation are related in that the hazard must be specified in terms that are meaningful to the vulnerability analysis.
|
From page 116... ...
CHARACTERIZATION OF GROUND SHAKING For historical and pragmatic reasons, MMI has been used as the ground-shaking measure in most earthquake loss studies conducted in the past, and likely will remam the standard for studies in the near future. This procedure was popular in early loss studies because multiple, instrumental records of ground shaking were not available to correlate motion levels to damage.
|
From page 117... ...
The use of MMI in loss estimates is a gross simplification that is justifiable only if more precise methods are not available. It is known, for example, that modifications of earthquake ground motions by soils are frequency dependent.
|
From page 118... ...
should be recognized as a less-than-perfect representation of earthquake ground shaking to be used only until more precise parameters and methods are available. HAZARD AND LOSS ESTIMATION PROCEDURES Scenario earthquakes have been deterrn~ned following rationales that in different ways express the need to compromise between the likelihood or credibility of the event and its destructive potential.
|
From page 119... ...
the heritage of early loss estimation efforts. Resistance to change has resulted from the difficulty of more complete representations of uncertainty and by computational constraints.
|
From page 120... ...
, but a description of uncertainty in the estimates for the scenario event may be included. Historic Maximum E:arthqu~ce Historic earthquakes, when judged to be suitable and perhaps with adjusted magnitude, intensity distribution, or location, can be used in loss estimation studies.
|
From page 121... ...
LOSS-FREQUENCY ANALYSIS FIGURE C-1 Form of results of different loss estimation techniques.
|
From page 122... ...
122 is the number per unit tune of earthquakes exceeding magnitude M, and a and b are coefficients typically estimated by statistical analysis. For example, the magnitude of earthquake expected to occur on the average once in every 100 or perhaps 500 years or more Knight be selected.
|
From page 123... ...
a function that estimates the intensity of ground motion at the site, for earthquakes of specified magnitudes and locations on the faults or sources.
|
From page 124... ...
is probability density, the summation is over all sources, i, that might produce ground motions affecting the site, pi represents the expected number of earthquakes per unit time in source i, and m and r are general descriptors of earthquake size (e.g., magnitude) and location tenth respect to the site (e.g., distance)
|
From page 125... ...
(log scale) FIGURE C-2 Graphs indicating probabilistic seismic hazard analysis steps.
|
From page 126... ...
Often the uncertainty in earthquake losses during a hypothesized earthquake is ignored, leading to a great simplification of equation 3. These uncertainties may result from variabilities in the ground motion generated at the site (whether or not this is used as an intermediate variable)
|
From page 127... ...
, and the seismic hazard results can be translated to loss estimates. In effect, this assumes that the region Is small enough that the same ground motion occurs over its entirety.
|
From page 128... ...
SU~RY This description of loss estimation methods is neither exhaustive nor exclusive, meaning that certain applications may require the development of specialized procedures not included in the present list or the combined use of several methods. Generally speaking, deterministic scenario analyses can be made at a level of detail and spatial resolution that is ~rnpractical in probabilistic risk calculations, because of the large number of calculations required by the latter methods.
|
From page 129... ...
profits as well as for the evaluation of the frequency of catastrophic losses. Another example is the comparison of risk reduction options: different risk reduction or preventive actions might have different effects depending on the earthquake size and the amount of damage.
|
From page 130... ...
Pre-existing files or data bases do not contain the amount or quality of information that is desired for the purpose of estimating earthquake losses. Inventories used for earthquake loss estimation purposes must be developed in a highly selective manner because this is the most time-consuming and costly step in the loss estimation process.
|
From page 131... ...
HIERARCHY OF DATA Based on recent loss estimations prepared by different methods and people, the best hierarchy of data items seems to be: ~ Facility location (addresses are preferred for buildings and structures, but they are often listed only by zip code or census tract; the census tract or other appropriate zone is used for linear or areawide facilities) ; Type of structure; Materialts)
|
From page 132... ...
Further, some kinds of inventory information are common for all loss estunation methods, that is, facility location, construction classification, occupancy data (number of occupants and type of occupancy or use) , and facility property value.
|
From page 133... ...
Once the facilities are described in terms of their location and construction class, and after construction classes are tied to motion-damage-Ioss relationships, this overall vulnerability analysis can be combined with the seismic hazard analysis to predict damage. Table 3-1 presented an example of a typical construction class system (see Chapter 33.
|
From page 134... ...
In a study of Los Angeles County earthquake losses by Scawthorn and Gates (1983) , except for construction data on high-r~se and unreinforced masonry buildings, inferences were used to convert land-use maps showing acreage of various uses into 13 construction classes and into building areas.
|
From page 135... ...
E~tunating losses for different tunes of day is typical of loss studies for this reason. Fortunately, census data, planning department studies or economic data, and reliable inferences relating the number of occupants to land-use or building area data (Jones, et al., 1986)
|
From page 136... ...
Because refinements in the geologic data base or changes in the analysis of seismic sources may occur and because the inventory may be useful for nonseismic purposes, it is always desirable to locate facilities according to a scale at least as fine as zip codes or census tracts, unless especialRy rapid and inexpensive studies are to be attempted. Since Bureau of the Census data include an enumeration of one- to four-family dwellings, dwelling lomes are generally estimated from an inventory that is already conveniently broken down into census tracts, block groups, and blocks.
|
From page 137... ...
Where local government assessors' files contain constructionrelated or other useful information, the assessor's parcel can be used as the basic mapping unit. Assessor's parcels conform to land ownership patterns, which are usually much finer-scaled in urban areas than zip codes or census tracts, or even census blocks.
|
From page 138... ...
None of these projects deal very specifically with the problem of enumerating buildings in terms of construction characteristics, which is by far the single biggest inventory problem in the earthquake loss estimation field. This is not what computerized approaches do best.
|
From page 139... ...
Many local organizations, such as utility companies, planning departments, emergency services departments, and others are investigating the potential of combining resources to produce multipurpose maps. SUGGESTED SOURC1:S OF INVENTORY INFORMATION Guidelines are suggested here for preparing rapidly an inventory of facilities when the preferred ideal inventory cannot be done for an earthquake loss estimation study.
|
From page 140... ...
. From earthquake loss estimate studies prepared by others and from examination of basic elements of loss estimation methods, some general guidelines for an inventory procedure can be inferred.
|
From page 141... ...
Unfortunately, most communities do not have data on these types of facilities that fulfill the construction data needs of an earthquake loss study inventory. Whatever information one finds for these types of facilities normally is ~ economic terms, for example, retail or industrial space in an area, employment by type of business, and sales volume.
|
From page 142... ...
Accordingly, the following previously stated position can be reiterated: If an earthquake loss estimate inventory is to be compiled, it is infinitely wiser in the long run to: Establish a systematic form for the needed end-data; Compile the data in a computer-retrievable form: ~ Record systematically the facility data by address or zone location; and Differentiate on the data record between those data that are real (correct or known) and those data that have been inferred.
|
From page 143... ...
It is usually possible to obtain inventories of the location, size, age, and approximate construction class of essential facilities such as police and fire stations or hospitals. Because of their unportance, as is the case with potentially high-hazard facilities, these essential facilities must be inventoried and field-rated on an individual basis.
|
From page 144... ...
Field visits are especially important for assessing the ability of an essential facility's equipment to function after an earthquake. About 800 of the University of California's major buildings, totaling 44 million square feet, have been seisrn~cally evaluated using a rapid rating process that essentially relied on the judgment of two experienced engineers, with a construction class system derived Tom the ISO scheme used as a guide.
|
From page 145... ...
The general exclusion of nonstructural damage seems to be more attributable to limited budgets rather than a disregard for the importance of this type of damage. The field evaluation method is based on a rating of components, rather than overall engineering judgment or overall construction class.
|
From page 146... ...
Where a given type of construction is of interest, such as unreinforced masonry, methods particular to this class are sometimes available. An early application of a component-rating system for purposes of rating unreinforced masonry buildings in a local government seismically hazardous building program (the first In the United States, beginning in the 1950s)
|
From page 147... ...
In some cases, such as the Salt Lake City study, a few classes of construction, such as unreinforced masonry, can be reliably predicted to account for a large part of the total losses (AIgerm~ssen and Steinbrugge, 1984) , and thus the inventory effort is more concentrated on these influential construction classes.
|
From page 148... ...
It is believed that the inventory obtained in Salt Lake City is extremely accurate for the purposes of an earthquake loss study and that the errors in the estimation of ground motion are likely to be much larger than the inventory errors in this particular study. In contrast, the inventory method for the San Etrancmco Bay Area was based on building information extrapolated from census data (dwellings)
|
From page 149... ...
was designed to provide Formation on damage, casualties, and immediate functional loss to be combined with an economic model for predicting economic losses, that is, direct building and structure lopes, loss of equipment, production losses, losses to infrastructures such as utilities and transportation systems, and losses due to interrupted business. To serve its original intended purpose, the inventory and loss estimates had to be compatible with the economic sectors to be used in the interindustry input-output model.
|
From page 150... ...
. The AT~13 report states its preferred source of inventory data as pre-existing inventories of facilities containing the required construction class detail, but because even less demanding classification systems cannot be supported by data that have already been collected, this preference will in most cases be unfulfilled.
|
From page 151... ...
This is also its biggest disadvantage compared to methods that use actual inventory data obtained from or checked by fieldwork with less extrapolation. The large amount of extrapolation and reliance on rules of thumb developed by combining the opinions of earthquake engineering experts can be seen from a typical example of how the inventory method would operate.
|
From page 152... ...
For the majority of buildings that remain, they can be divided into mid-rise and low-rise categories based on rules of thumb developed by a process of asking earthquake engineering experts their opinions. In this third step of developing a synthetic construction class distribution, the other basic task is to assign a construction class (e.g., reinforced masonry shear wall with moment-resisting frame, reinforced masonry shear wall without moment-resisting frame)
|
From page 153... ...
Steps one and two involve relatively noncontroversial extrapolations common to many loss estimation methods. It ~ the third step, where the inventory variable of central importance construction class is synthesized on the basis of opinion, that involves untested relationships.
|
From page 154... ...
The lists shown in Table D-1 are in a different form than they appear in either method and are organized more generically to allow for comparisons. For example, the NOAA-USGS approach contains a class for mixed construction (different was and diaphragm material)
|
From page 155... ...
unreinforced masonry buildings was already in existence because of the city's retroactive seismic ordinance, and the characteristics of high-rme buildings were tabulated in a real estate survey. Census data on population and housing from the 1980 census were used, along with a 1974 city study.
|
From page 156... ...
Another problem was that this data base was not current because the cost of updating it had been considered too high by the planning department a few years after it had been created. POSTEARTlIQUA1lE STUDIES OF LOSS Related to the pre-earthquake inventory problem ~ the task of postearthquake inventory of damage by class of construction, location, ground conditions, and intensity or measured ground motion.
|
From page 157... ...
Earthquake damage can only be estimated accurately when building construction data are directly sought. Converting economic data into construction cIassification data ~ not recommended because this can greatly reduce the accuracy of the inventory.
|
From page 158... ...
158 Department of insurance obtain this Information, aggregated by geographic zone and clam of construction, on an annual basis. 0~ tanning some of this information would benefit national or regional interests, solve some of the data problems of earthquake damage estimating, and yet-preserve such proprietary information as the industry deems necessary.
|
From page 159... ...
Working Paper D explained that the construction classification system is a part of both the inventory process and the motion-damage analysis step because the inventory information must be collected with the same construction classes used in relating the seismic hazard to construction classes through motion-damage relationships. Many methods of relating ground motion, or less commonly ground failures, to damage have been proposed or developed.
|
From page 160... ...
The ATC-13 method uses the format of the damage probability matrix to present its damage estimates for each MMI level: the percentage of facilities that wouic] fall into each of seven damage levels is given for each construction class (with these damage levels described verbally, with property damage ratio ranges, and with central damage ratios)
|
From page 161... ...
The truncation of the mean damage ratio curve at MMI X-X is due to the fact that intensities above this point have sometimes been assigned to sites in previous earthquakes on the basis of ground failure, not ground shaking. Table ~1 briefly tabulates the construction classes.
|
From page 162... ...
Mean damage ratios are used because they are average factors for all buildings of given classes. They do not give the distribution of damage, such as how many buildings had little or no damage or how many had moderate damage.
|
From page 163... ...
Reinforced concrete, precast reinforced concrete, lift slab Reinforced concrete, floors and roofs not concrete Mixed construction, small buildings and dwellings Mixed construction, superior damage control features Mixed construction, ordinary damage control features Mixed construction, intermediate damage control features Mixed construction, unreinforced masonry Buildings specifically designed to be earthquake resistant SOURCE: Algermissen and Steinbrugge, (1984~. For more complete descriptions of each class, see Iso (1977)
|
From page 164... ...
Figure ~2 shows some of the mean damage ratio curves used in the NOAA-USGS method. The amount of historic damage data available on some of the classes of construction, particularly wood-frame dwellings, is extensive, whereas more judgment and fewer data are employed to develop damage ratios for high-rise buildings or many low-rise commercialindustrial construction classes for which there is less experience.
|
From page 165... ...
. ATC-13 MOTION-DAMAGE RELATIONSHIPS The ATC-13 method does not describe its building construction classes in as much detail as in the NOAA-USGS scheme, but includes many structures that are not addressed in the NOAA-USGS method.
|
From page 166... ...
Low rise Medium rise High rise Reinforced masonry shear wall (with moment-resisting frame) Low rise Medium rise High rise Braced steel frame Low rise Medium rise High rise Moment-resisting steel frame (perimeter frame)
|
From page 167... ...
Low rise Medium rise High rise Precast concrete (other than tilt-up) Low rise Medium rise High rise Long-span (low rise)
|
From page 168... ...
Electrical Mechanical High technology and laboratory Trains, trucks, airplanes, and other vehicles 47 48 49 50 51 52 53 54 55 56 57 58 59 61 62 63 64 65 66 68 70 90 SOURCE: Applied Technology Council (1985)
|
From page 169... ...
MMI XI and XIT are used here to refer to increasingly severe ground motion, beyond the X-X point; this is not a literal interpretation of the scale's reference to ground failure indicators at these highest two intensities. Examples of damage probability matrices produced by expert opinion in the ATC-13 project are shown in Table ~4.
|
From page 170... ...
SOURCE: Applied Technology Council (1985~.
|
From page 171... ...
In this case, it ~ a general class of "all wood-frame buildings" which would be applicable where distinctions between above and below standard wood-frame buildings cannot be made. Figure ~3 illustrates that for earthquake intensity MMI ~X, there is a: 0.95 probability of at least nonstructural damage, 0.91 probability of at least slight structural damage, 0.23 probability of at least moderate structural damage, and 0.01 probability of at best severe structural damage, and 0.00 probability of collapse (Kircher and McCann, 1983~.
|
From page 172... ...
\ LL oh of o 1 u)
|
From page 173... ...
While damage probability matrices can be converted into fragility curves, there is a difference in the supporting foundations upon which the motion-damage relationships were based in the studies. In the Six Cities study, calculations of structural capacities were made for a given class of construction.
|
From page 174... ...
76 52.9 Unreinforced masonry 4B 25 Vertical frame, Vertical frame nonbearing Low (1-3) 78 27.5 walls Medium (4-7)
|
From page 175... ...
82 23.8 High (> 8) 83 28.8 Long span/low rise 91 6.6 Mobile home 23 13.9 KVS (133 Extrapolated SOURCE: Degenkolb (1986)
|
From page 176... ...
In o 1 z o z \= ~ ~-~ it\\ ~ - - \ _ an _ as I\ \ LL 45: cn x x z ~ o ~ An A · ~ IL IL ~ J z LL — J Z I,]
|
From page 177... ...
This value represents the initiation of moderate structural damage. Step 7: Estimate the base shear value for the building corresponding to the ultimate capacity of all lateral-force resisting elements.
|
From page 178... ...
This detailed description of construction classes allows the use of expert opinion to be focused on the same precise question and also allows other investigators to apply or convert the motion-damage relationships with confidence as to the departure point. All three other major methods reviewed here could benefit from this careful documentation of construction class definitions.
|
From page 179... ...
~ r: ~ ~ '`` 1: ~~ / FIGURE ~5 Definition of one construction class (attached three-story rowhouse)
|
From page 180... ...
180 = _ 4.,~ ~ 2"~;10" Joists _~_ be ~ ~: nut ~ -I ~,~1_ ~~ L,c'aI,:~" ~12" 4" 20" A /~ //~ FIGURE ~5 (Continued)
|
From page 181... ...
181 Plas ter F FIGURE ~5 (Continued)
|
From page 182... ...
182 ~ I I I I I I D U if 1 1 I _ l , ` \ Interior Transverse —Party Wal is (Masonry ) _ 1, ~ , ~ _ I Interior Transverse Stud Wall ~L''~ Bas even t tNeam L ~ (column stem | ~ .
|
From page 183... ...
notes, earthquake loss estimation methods are cheap but the information required to make them work · ~ IS eXpenSlVe. Every method must face the question of where to limit itself in attempting to produce quantitative estimates how far to push expert opinion, educated guesses based on suggestive but inconclusive data, or relatively untested extrapolations.
|
From page 184... ...
The number of use classes could be greatly reduced, because for most emergency planning and hazard reduction purposes, the fine distinctions between various commercial and industrial economic sectors wiD not be used. In some cases, greater definition of essential emergency services facilities would be desirable, but this relates to facility-specific field surveys that are not discussed in ATC-13.
|
From page 185... ...
Although the synthesis of construction data from economic or social data bases is to some extent necessary in any method, AT~13's extensive reliance on this approach, primarily for budgetary reasons, emerges as a limitation. Other large-scale loss estimation studies have afforded the cost of at least some fieldwork to assemble information on key facilities, to sample areas to develop extrapolations that can be relied on as valid for a particular reg~on's inventory of facilities, and to check at least some of the existing file data's accuracy.
|
From page 186... ...
The fragility curve approach of the Six Cities study also attempts to portray at least some of its uncertainties. Whether damage probability matrices or fragility curves are the best way to represent loss estimates is an issue apart from the point that the explicit accounting for uncertainty must be attempted by all methods.
|
From page 187... ...
casualty statistics from previous earthquakes, rather than to relate casualties directly to damage or property loss estimates. The NOAA-USGS studies, for example, generally applied one casualty rate to wood-frame dwellings and one or more other rates to other kinds of construction.
|
From page 188... ...
on dwelling losses was also used, and this study essentially used a damage probability matrix: for each MMI, and for each damage ratio range, the percentage of buildings falling in that MMI/damage cell was produced. This indicates that seemingly clear lines of demarcation between different methods become blurred on closer examination and emphasizes the potential In developing hybrid methods that combine the best elements of different methods.
|
From page 189... ...
Temporary homelessness was estimated according to intensity for eight construction classes, and permanent homeless caseload figures, related to irreparably damaged dwellings, were estunated for the higher damage ratios. Evans and Arnold (1986)
|
From page 190... ...
, in which 38 of the 78 total construction classes are nonbuilding structures and most of these 38 classes are related to lifelines. Lifeline service outage estimates can be stated in various ways.
|
From page 191... ...
Losses in the level of service provided by the lifeline should take into account a noneng~neering factor that may be difficult to evaluate: the emergency response capability of the lifeline operator or of other emergency response agencies. A utility with an earthquake-resistant radio system, personnel who undergo annual earthquake exercises to test their ability to carry out preassigned tasks, and back-up plans for handling significant damage beyond that occurring in weatherrelated incidents, should be much more able to contain the impact of earthquake damage than another utility without these attributes.
|
From page 192... ...
The Applied Technology Council (1985) reviewed the field in the process of developing ways to deal with the problem of estunating lifeline losses, and another broad review of the field from the hazard reduction perspective is provided by the Building Seismic Safety Council (1987~.
|
From page 193... ...
As shown in Table ~5, the most extreme discrete ancy between the NOAA-USGS and ATC-13 estimates is for tilt-up structures, where ATC-13 shows a mean damage ratio of 15.8 percent, compared to 30 percent in NOAA-USGA. All other structural types show a much closer level of agreement.
|
From page 194... ...
The same is true for the effects of ground motion. Use of the Modified Mercalli Scale, with all its limitations, still matches the available Carnage information.
|
From page 195... ...
Working Paper F Liquefaction and Landslides LIQUEFACTION As applied to seismic problems, liquefaction has become a catchall word referring to various types of earthquake-caused failures of saturated cohesionless soils. Four different Manifestions of liquefaction have been identified (National Research Council, 1985~: 1.
|
From page 196... ...
(1978~. Other examples appear in ATC-13 (Applied Technology Council, 1985~.
|
From page 197... ...
It is unlikely that a program of penetration tests would be undertaken in connection with a large-scale loss estimation study. However, data from previously drilled borings can be used to evaluate the liquefaction susceptibility of deposits in a study area and thus serve as a basis for preparing liquefaction hazard maps.
|
From page 198... ...
While these techniques are of value for evaluating specific sites or particular earth structures (e.g., earth dams) , they are not appropriate for large-scale loss estimation studies.
|
From page 199... ...
05 8 O 04 .o = cr v' Cal — c ° .
|
From page 200... ...
is 5 to 10 times greater than damage to buildings on firm ground, for the same intensity of ground motion. Thus, for facilities on the surface, the ATC report proposes to evaluate a mean damage ratio (MDR)
|
From page 201... ...
201 12 1 1 10 Cal I , 8 CO a)
|
From page 202... ...
0.5 2 5 7 12 25 40 3 Late Pleistocene Alluvium 0.1 0.5 1 2 4 7 10 aEstimates are based on consensus of the ATC-13 Project Engineering Panel. SOURCE: Applied Technology Council (1985)
|
From page 203... ...
203 TABLE F-3 Qualitative Assessment of Abundance and General Character of Liquefaction Effects as a Function of LSI for Areas with Widespread Liquefiable Deposits LSI Abundance and General Character of Liquefaction Effects 10 30 70 90 5 Very sparsely distributed minor ground effects include sand boils with sand aprons up to 0.5 m (1.5 It) in diameter, minor ground fissures with openings up to 0.1 m wide, ground settlements of up to 25 mm (1 in.~.
|
From page 204... ...
(1982) , and utilizing expert opinion, ATC developed the probability matrices reproduced in Table F-6.
|
From page 207... ...
3 0 ~ ~ ° 3 sat— At, Act Q oo o ~ ~ '" Ct ~ ~ S =~ ~ .= X ~ ~ ~ X ~ ,= X ~ X ~ X ~ a.
|
From page 208... ...
Thus, the mean damage ratio from landslides is: MDRL,s = As, PtSFS] x CDF~s, SFS where PtSFS]
|
From page 209... ...
- ~ or o · · o v L' en - ~ *
|
From page 211... ...
The other factor determining the assignment of a site into one of the four zones was the critical acceleration causing the movement. For each of these four levels of susceptibility, an estimate is provided of the percentage of the area of that zone that would fait when the presumed earthquake occurs.
|
From page 212... ...
These authors also used Newmark's sliding block theory to relate the likelihood of slides to the intensity of ground motions, and produced a map (see Figure F-5) giving the probability of coherent slides (in either hilly terram or saturated soils)
|
From page 213... ...
l i I I I I I I I T~ I \ ~ · I \ - e Y \~ · \ C \ ~ CO—4% cr.
|
From page 216... ...
Rather, it reflects the difficulties involved in conducting a comprehensive economic accounting of the effects of an earthquake. The preceding working papers clearly demonstrate the complexities surrounding procedures for estimating direct earthquake losses.
|
From page 217... ...
Estimates of the direct property losses follow in a straightforward fashion from damage estimates, but the other two types of losses warrant some further discussion. As a first approximation to losses from premature mortality, Sorkin (1982)
|
From page 218... ...
One major difference is the level of detail attempted in terms of the number of construction classes and the classification of economic and social function. The attempt to add detail to the damage relationships by consulting a number of experts was unique, as was the attempt to generate a comprehensive inventory from socioeconomic data in automated form available from FEMA.
|
From page 219... ...
If the first phase of the ATC-13 methodology could be implemented at this level of detail, then some initial estunates of loss of function to defense related or other ~critical" industries might be possible. However, these direct damage and loss estimates ignore important secondary effects throughout the economy after catastrophic events.
|
From page 220... ...
220 activities bring with them an influx of financial resources (e.g., from government recovery and relief efforts, and insurance cIaims) that increases the demand for the output of certain sectors, particularly construction.
|
From page 221... ...
(8) In the planned second phase of the economic study, FEMA would make use of the direct damages and loss estimates coming out of the AT~13 method.
|
From page 222... ...
is in place, on the basis of the initial direct loss estimates, procedures would be developed to estimate new levels of fin e] demand, Y
|
From page 223... ...
At a minimum, researchers should collect inventory information that relates construction class to economic and social function or undertake specific research to establish any systematic relationships that Knight exist. Furthermore, to be useful for hazard reduction, emergency planning, and recovery planning efforts, the level of detail in terms of econorn~c and social function does not need to be fine enough to differentiate all 470 sectors.
|
From page 224... ...
as they may apply to earthquake loss estimation. Synopsis of presentation to the Earthquake Loss Estimation Panel, January 8, 1987, National Research Council, Washington, D.C.
|
From page 225... ...
1982. Earthquake Damage and Loss Estimation: Review of Available Methods.
|
From page 226... ...
1986. Notes prepared for the Panel on Earthquake Loss Estimation, May 28-29, 1986.
|
From page 227... ...
1984. Appendix A: Development of Seismic Fragility Curves for Sixteen Types of Structures Common to Cities of the Mississippi Valley Region.
|
From page 228... ...
1986. Use of ATC-13 damage probability matrices for a seismic risk analysis of the Boston metropolitan area.
|
From page 229... ...
1976. A Study of Earthquake Losses in the Salt Lake City, Utah Area.
|
From page 230... ...
1973. Earthquake damage probability matrices.
|
From page 231... ...
1987. Comments on the fourth meeting of the Panel on Earthquake Loss Estimation, National Research Council, January 8-9, 1987, Washington, D.C.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.