ASTM E2557-16a

Standard Practice for Probable Maximum Loss (PML) Evaluations for Earthquake Due-Diligence Assessments<rangeref></rangeref >

SIGNIFICANCE AND USE
5.1 This practice is intended for use as a voluntary standard by parties who wish to undertake the seismic risk assessment of properties. The goal is for users to objectively and reliably compare the financial risks of earthquake damage to buildings, or groups of buildings, on a consistent basis.  
5.2 This practice is designed to provide requirements for the evaluation of earthquake damage risk so that technical reports prepared for the evaluation and rating of seismic risk of a building(s) will be adequate for use by other entities. Potential users including, but are not be limited to, those making equity investments, lending, and financial transactions, including securitized mortgage lending by mortgage originators, loan servicers, underwriters, rating agencies, and purchasers of bonds secured by the real estate.  
5.3 The use of this practice may permit a user to satisfy, in part, their requirements for due diligence in assessing a property's potential for losses associated with earthquakes for real estate transactions.
SCOPE
1.1 This practice establishes standard-of-care for evaluation and classification of the financial risks from earthquake damage to real estate improvements for use in financial mortgage transactions and capital investment evaluation. As such, this practice permits a user to satisfy, in part, their real estate transaction due-diligence requirements with respect to assessing and characterizing a property’s potential losses from earthquakes. This practice is intended to address only physical damage to the property from site and building response.  
1.1.1 Hazards addressed in this practice include earthquake ground shaking, earthquake-caused site instability, including faulting, subsidence, settlement landslides and soil liquefaction, earthquake-caused tsunamis and seiches, and earthquake-caused flooding from dam or dike failures.  
1.1.2 Earthquake-caused fires and toxic materials releases are not hazards considered in this practice.  
1.1.3 This practice does not purport to provide for the preservation of life safety, or prevention of building damage associated with its use, or both.
1.1.3.1 This practice does not address requirements of any federal, state, or local laws and regulations of building construction or maintenance. Users are cautioned that current federal, state, and local laws and regulations may differ from those in effect at the times of construction or modification of the building(s), or both.
1.1.3.2 This practice does not address the contractual and legal obligations between prior and subsequent Users of seismic risk assessment reports or between providers who prepared the report and those who would like to use such prior reports.
1.1.3.3 This practice does not address the contractual and legal obligations between a provider and a user, and other parties, if any.  
1.1.4 It is the responsibility of the owner of the building(s) to establish appropriate life-safety and damage prevention practices and determine the applicability of current regulatory limitations prior to use.  
1.2 Considerations not included in the scope: the impacts of damage to contents, loss of income(s), rents, or other economic benefits of use of the property, or from legal judgments, fire sprinkler water-induced damage or fire.  
1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.

General Information

• Status: Published
• Publication Date: 14-May-2016
• ICS: 03.060 - Finances. Banking. Monetary systems. Insurance
• Technical Committee: E06 - Performance of Buildings
• Drafting Committee: E06.25 - Whole Buildings and Facilities

Relations

• Replaces: ASTM E2557-16 - Standard Practice for Probable Maximum Loss (PML) Evaluations for Earthquake Due-Diligence Assessments<rangeref></rangeref >
• Effective Date: 15-May-2016
• Refers: ASTM E2026-16a - Standard Guide for Seismic Risk Assessment of Buildings
• Effective Date: 15-May-2016
• Refers: ASTM E2026-16 - Standard Guide for Seismic Risk Assessment of Buildings
• Effective Date: 01-Jan-2016
• Refers: ASTM E2026-07 - Standard Guide for Seismic Risk Assessment of Buildings
• Effective Date: 01-May-2007
• Refers: ASTM E2026-99 - Standard Guide for the Estimation of Building Damageability in Earthquakes
• Effective Date: 10-Jul-1999

Overview

ASTM E2557-16a, Standard Practice for Probable Maximum Loss (PML) Evaluations for Earthquake Due-Diligence Assessments, provides a structured approach for evaluating the financial risks posed by potential earthquake damage to real estate. This standard supports stakeholders in the real estate, finance, and insurance industries as they assess and compare the seismic risk associated with properties and portfolios. By promoting objective, transparent, and consistent analysis, ASTM E2557-16a facilitates informed financial decisions concerning buildings subject to earthquake hazards.

Key Topics

• Probable Maximum Loss (PML): Central to the standard, PML is the estimated maximum expected financial loss from earthquake-induced physical damage to buildings or groups of buildings, considering site and structural response.
• Seismic Risk Assessment: Requirements for evaluating vulnerability to ground shaking, site instability (faulting, liquefaction, landslides), tsunami, seiche, and earthquake-induced flooding (from dam or dike failure).
• Report Preparation and Reliance: Defines minimum content for PML technical reports, including site/building characterization, levels of investigation, summary of findings, and disclosure of professional qualifications.
• Levels of Investigation: Outlines different depths of evaluation (from Level 0 - documentation review only, to Level 3 - in-depth analysis and site visits) to match the complexity of the property and risk tolerance.
• Due Diligence for Financial Transactions: Guidance prepares users to meet lender, investor, and regulatory due diligence requirements related to seismic risk.
• Exclusions: The standard focuses exclusively on physical damage; it does not cover life safety, toxic releases, fire, or losses to contents or income.

Applications

ASTM E2557-16a is widely used in the context of:

• Equity Investments and Lending: Enables objective earthquake risk analysis to inform lending or investment decisions in real estate transactions, including commercial mortgage-backed securities (CMBS).
• Financial Risk Management: Assists financial institutions, loan servicers, bond purchasers, underwriters, and rating agencies in understanding and quantifying exposure to earthquake risk in their property portfolios.
• Insurance and Reinsurance: Provides a benchmark for assessing probable maximum loss, underpinning insurance coverage decisions and premium calculations for earthquake risk.
• Real Estate Transactions: Supports buyers, sellers, and investors in evaluating potential losses as part of pre-acquisition or refinance due diligence.
• Capital Investment Analysis: Informs decisions on seismic retrofits or site selection by quantifying risk and identifying stability issues.

Related Standards

ASTM E2557-16a is designed to be used in conjunction with several other benchmarks for seismic risk and structural performance, including:

• ASTM E2026: Guide for Seismic Risk Assessment of Buildings, which provides much of the terminology and framework referenced by E2557-16a.
• ASCE 7: Minimum Design Loads for Buildings and Other Structures, specifying loading requirements for structural design.
• ASCE 41: Seismic Evaluation and Retrofit of Existing Buildings, setting standards for the assessment and retrofit of at-risk structures.
• International Building Code (IBC) and UBC-97: U.S. model building codes specifying seismic design criteria, referenced for hazard level definitions and context.

Practical Value

ASTM E2557-16a delivers multiple benefits to stakeholders in the built environment:

• Consistency & Transparency: Ensures seismic risk assessments are performed and reported in a uniform, comparable manner.
• Credibility: Advises on assessor qualifications, levels of investigation, and due diligence, reducing uncertainty in outcomes.
• Decision Support: Provides tools to distinguish acceptable and unacceptable seismic risks for real estate investment and lending.
• Risk Communication: Structured reporting and terminology facilitate clear communication of complex seismic risk data to non-specialists.

Keywords: ASTM E2557-16a, Probable Maximum Loss, earthquake due diligence, seismic risk assessment, PML evaluation, real estate transaction, financial risk, site stability, building stability, Level of Investigation, insurance, mortgage lending, capital investment, ASTM E2026, ASCE 7, ASCE 41, IBC.

For organizations seeking to align their property risk assessments with industry best practice, ASTM E2557-16a is a critical reference for ensuring comprehensive, reliable, and actionable earthquake loss evaluations.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E2557 − 16a
Standard Practice for
Probable Maximum Loss (PML) Evaluations for Earthquake
1,2
Due-Diligence Assessments
This standard is issued under the fixed designation E2557; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.1.4 It is the responsibility of the owner of the building(s)
to establish appropriate life-safety and damage prevention
1.1 This practice establishes standard-of-care for evaluation
practices and determine the applicability of current regulatory
and classification of the financial risks from earthquake dam-
limitations prior to use.
age to real estate improvements for use in financial mortgage
transactions and capital investment evaluation. As such, this 1.2 Considerations not included in the scope: the impacts of
practice permits a user to satisfy, in part, their real estate damagetocontents,lossofincome(s),rents,orothereconomic
transaction due-diligence requirements with respect to assess- benefits of use of the property, or from legal judgments, fire
ing and characterizing a property’s potential losses from sprinkler water-induced damage or fire.
earthquakes. This practice is intended to address only physical
1.3 The values stated in inch-pound units are to be regarded
damage to the property from site and building response.
as standard. The values given in parentheses are mathematical
1.1.1 Hazards addressed in this practice include earthquake
conversions to SI units that are provided for information only
ground shaking, earthquake-caused site instability, including
and are not considered standard.
faulting, subsidence, settlement landslides and soil
liquefaction, earthquake-caused tsunamis and seiches, and
2. Referenced Documents
earthquake-caused flooding from dam or dike failures.
2.1 ASTM Standards:
1.1.2 Earthquake-caused fires and toxic materials releases
E2026 Guide for Seismic Risk Assessment of Buildings
are not hazards considered in this practice.
2.2 Other Standards:
1.1.3 This practice does not purport to provide for the
UBC-97 Uniform Building Code, 1997 Edition
preservation of life safety, or prevention of building damage
IBC International Building Code, current edition
associated with its use, or both.
2.3 ASCE Standards:
1.1.3.1 This practice does not address requirements of any
ASCE 7 Minimum Design Loads for Buildings and Other
federal, state, or local laws and regulations of building con-
Structures, current edition
struction or maintenance. Users are cautioned that current
ASCE 41 Seismic Evaluation and Retrofit of Existing
federal, state, and local laws and regulations may differ from
Buildings, current edition
those in effect at the times of construction or modification of
the building(s), or both.
3. Terminology
1.1.3.2 This practice does not address the contractual and
3.1 See also definitions in Guide E2026.
legal obligations between prior and subsequent Users of
seismic risk assessment reports or between providers who
3.2 475-year site ground motions, n—seismic induced
prepared the report and those who would like to use such prior
ground motions at a site with approximately: a return period of
reports.
475years,a10 %probabilityofexceedancein50years,andan
1.1.3.3 This practice does not address the contractual and
annual frequency of 0.21 %. Also referred to as the DBE.
legal obligations between a provider and a user, and other
3.3 field assessor, n—field assessor, as defined in Guide
parties, if any.
E2026.
This practice is under the jurisdiction of ASTM Committee E06 on Perfor-
mance of Buildings and is the direct responsibility of Subcommittee E06.25 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Whole Buildings and Facilities. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Current edition approved May 15, 2016. Published June 2016. Originally Standards volume information, refer to the standard’s Document Summary page on
approved in 2007. Last previous edition approved in 2016 as E2557-16. DOI: the ASTM website.
10.1520/E2557-16A. Available from International Code Council (ICC), 500 New Jersey Ave., NW,
Portions of this publication reproduce content from the 1997 Uniform Building 6th Floor, Washington, DC 20001, http://www.iccsafe.org.
Code, International Code Council, Inc., Falls Church, Virginia. Reproduced with Available from American Society of Civil Engineers (ASCE), 1801 Alexander
permission. All rights reserved. Bell Dr., Reston, VA 20191, http://www.asce.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2557 − 16a
3.4 independent reviewer, n—independent reviewer, as de- 5. Significance and Use
fined in Guide E2026.
5.1 This practice is intended for use as a voluntary standard
3.5 lateral load-resisting system, n—lateral load-resisting bypartieswhowishtoundertaketheseismicriskassessmentof
system, as defined in Guide E2026. properties. The goal is for users to objectively and reliably
compare the financial risks of earthquake damage to buildings,
3.6 MCE, n—Maximum Capable Earthquake, as defined in
or groups of buildings, on a consistent basis.
Guide E2026.
5.2 Thispracticeisdesignedtoproviderequirementsforthe
3.7 probable loss (PL), n—probable loss, as defined in
evaluation of earthquake damage risk so that technical reports
Guide E2026.
prepared for the evaluation and rating of seismic risk of a
3.7.1 Discussion—When there are multiple buildings in the
building(s) will be adequate for use by other entities. Potential
seismic risk assessment, then the damageability values for the
users including, but are not be limited to, those making equity
group of buildings is to be determined as specified in Guide
investments, lending, and financial transactions, including
E2026.
securitized mortgage lending by mortgage originators, loan
3.8 probable maximum loss (PML), n—probable maximum
servicers, underwriters, rating agencies, and purchasers of
loss, as defined in Guide E2026.
bonds secured by the real estate.
3.9 provider, n—provider, as defined in Guide E2026.
5.3 The use of this practice may permit a user to satisfy, in
part, their requirements for due diligence in assessing a
3.10 scenario expected loss (SEL), n—scenario expected
property’s potential for losses associated with earthquakes for
loss, as defined in Guide E2026.
real estate transactions.
3.10.1 Discussion—When there are multiple buildings in
the assessment then the SELfor the group of buildings is to be
6. Due-Diligence Investigation
determined as specified in Guide E2026, Section 5.3.
6.1 The site stability, building stability and building dam-
3.11 scenario loss (SL), n—scenario loss, as defined in
ageability of the property shall be assessed.
Guide E2026.
6.2 Theusershallspecifytheconditionofthepropertytobe
3.11.1 Discussion—When multiple buildings are in the seis-
evaluated. The seismic performance can be evaluated for the
mic risk assessment, then the SL for the group of buildings is
property in its current condition, or as changed by proposed
to be determined as specified in Guide E2026, Section 5.3.
modification of the seismic response of the soils supporting the
3.12 scenario upper loss (SUL), n—scenario upper loss, as
building or a proposed seismically retrofitted condition of the
defined in Guide E2026.
building(s) or its sections, or any combination of these condi-
3.12.1 Discussion—When there are multiple buildings in
tions.
the assessment then the SULfor the group of buildings is to be
6.2.1 The proposed seismic modifications of the site must
determined as specified in Guide E2026, Section 5.3.
be sufficiently described to allow evaluation of the modifica-
3.13 SEL475, n—the scenario expected loss due to the tions by an Independent Reviewer.
occurrence of 10 %/50-year site ground motions. 6.2.2 The proposed seismic modifications of the building
systems must be sufficiently described to allow evaluation of
3.14 SEL ,n—the scenario expected loss due to the
MCE
the modifications by an Independent Reviewer.
occurrence of MCE site ground motions.
6.3 The Guide E2026 level of investigation shall be speci-
3.15 senior assessor, n—seniorassessor,asdefinedinGuide
fied by the user. The same level of investigation should be
E2026.
performed for each type of the seismic risk assessment.
3.16 significant damage, n—significant damage, as defined
Appendix X2 gives guidance on the setting of the level of
in Guide E2026
investigation.
3.17 SUL475, n—the scenario upper loss due to the occur-
6.4 The qualifications of the Provider shall be specified as
rence of 10 %/50-year site ground motions.
required for the level of investigation specified in 6.3 of Guide
E2026.The qualifications level must be equal to or higher than
3.18 SUL ,n—the scenario upper loss due to the occur-
MCE
the corresponding level specified in 6.2 and 6.3. Appendix X1
rence of MCE site ground motions.
gives further guidance on the setting of minimum qualifica-
tions.
4. Summary of Practice
6.4.1 For an assessment of Level 1 or higher, the qualifica-
4.1 The objectives of this practice are as follows:
tions of SeniorAssessor and the FieldAssessor of the property
4.1.1 To synthesize and document good commercial prac-
and its buildings shall be those of Guide E2026 Sections
tice for the determination and rating of seismic risk for
6.2.3.2 and 6.2.3.3.
buildings.
6.4.2 Notwithstanding the asserted level of investigation of
4.1.2 To facilitate standardization of earthquake risk evalu-
a report, if the Senior Assessor or the Field Assessor, or both,
ation terminology for financial transactions.
do not demonstrate the qualifications of Guide E2026 Section
4.1.3 To establish an industry standard for the requirements 6.2.3.2 and 6.2.3.3, then the report shall be designated a Level
to evaluate the financial risk for real estate. 0 report.
E2557 − 16a
6.5 Seismic Risk Assessment Report—The findings shall be 6.5.1.7 Appropriate reliance language for the report and
reported in conformance to the requirements of Guide E2026 signature.ForLevel1orhigherinvestigations,theprofessional
for the level of investigation specified by the user in 6.3 and by seal of the provider.
aproviderqualifiedinaccordancewiththerequirementsof6.4, 6.5.1.8 All deletions and deviations from this practice (if
with the following sections: any) shall be listed individually and in detail.
6.5.1.9 The report conclusion shall include the following
6.5.1 A summary that contains the conclusions of the
statement: “We have performed a probable maximum loss
seismic risk assessment:
(PML) evaluation for earthquake due diligence assessment in
6.5.1.1 Location of the building(s), characterization of the
conformance with the scope and limitations of Guide E2026
site and site soils, and gravity and lateral load-resisting
and Practice E2557 for a Level XX (specify) assessment of
systems.
[insert address or legal description], the property. Any excep-
6.5.1.2 Stability determination of each building site under
tions to, or deletions from, this practice are described in
consideration when subjected to the seismic loadings for the
Section[]of this report. This probable maximum loss (PML)
buildingsitelocationandbuildingcharacteristicsassetforthin
evaluation for earthquake due diligence assessment has deter-
Section 9 of Guide E2026. Site stability determination need
mined the PML to be [ ]%.” PML is defined as [fill in the
only be qualitative in nature for an SS0 investigation. For SS1
definition used]. The project [meets/does not meet] the build-
investigations the site stability is a qualitative assessment that
ing stability and [meets/does not meet] the site stability
includes the implications on damage to the building structural
requirements.
elements. For SS2 and SS3 investigations the site should be
6.5.1.10 Each report should include a completed Appendix
considered unstable if significant damage is caused to the
X4.
building by the site instability.
6.5.1.11 Each report should include a completed Appendix
6.5.1.3 Stability determination of each building under con-
X5.
sideration in the seismic loadings for the building site location
6.5.2 A body of the report that provides:
and building characteristics and for the level of investigation
6.5.2.1 AlldetailedreportinginformationrequiredbyGuide
specified, as set forth in Section 8 of Guide E2026.
E2026, Section 13, including the basis and background for the
6.5.1.4 The building damageability values for the building
work performed in support of the conclusions presented in the
or group of buildings as a whole for the level of investigation
report.
specified as set forth in Section 10 of Guide E2026.
6.5.2.2 PML values for each building, and, if appropriate,
(1) PMLshall be user-defined.At a minimum, the SEL
DBE
for the group of buildings.
and SUL shall be reported.
DBE
(1) Report of any other information required by the user,
which may include business interruption, and contents dam-
NOTE 1—CMBS industry is currently defining PML as SEL .Itis
DBE
advisable that SEL and SUL values also be reported for MCE events in
ageability.
areasoflowandmoderateseismicityareaswhereMCEposessignificantly
(2) The organization that commissioned the report and the
higher risk than the DBE.
professional liability limitations of the report provider shall be
6.5.1.5 Aspecification of the level of investigation for each
disclosed in the report.
assessmentandareviewofthemethodsusedandthepersonnel
6.5.3 Attachments and appendices to the report as appropri-
engaged.
ate including detailed resumes of the Senior Assessor and the
6.5.1.6 Results for each of the conditions described in 6.2 FieldAssessor that demonstrate their qualifications to perform
that apply. this work as stated in this Practice.
E2557 − 16a
APPENDIXES
(Nonmandatory Information)
X1. GUIDANCE FOR USE OF E2557
INTRODUCTION
This Appendix provides guidance to decision makers for sorting their way through the intricacies
of seismic risk assessment. Usually a due-diligence financial decision is posed as should the
transaction be considered further or not? A PML assessment is commissioned to understand if there
is a seismic hazard at the property and the extent of the risk it poses. The process used to complete
PMLassessments should consider the various sources of uncertainty as well as the financial and other
consequences that may arise when a good building is called ‘bad’ (Type I error), or when a bad
building is called ‘good’ (Type II error). An error of the first type precludes a possibly profitable
investmentbutotherwiseisbenigninthatitdoesnotleadtoaloss,whereasthelattererrorhasahigher
riskthanisnominallyacceptableandmayleadtolargeloss.TypeIIerrorsleadtounexpectedlyhigher
risks and should be minimized consistent with other objectives of the User. Experience of theASTM
Committee members suggests that the likelihood ofType II errors is highest in (1) Level 0 reports, (2)
reports issued by individuals that are not sufficiently knowledgeable and experienced at any level, and
(3) reports where the structural documents were not reviewed. If the result of the assessment is
unacceptable to the risk profile of the User and the economics of the deal are still attractive, then the
determination can only be made to pursue more, better quality and more reliable information and
assurance of qualified performers for the specific property. The goal should be to reach conclusions
that give reasonable control of Type II errors, but are not so risk adverse as to reject investments that
would be prudent and profitable that otherwise have acceptable seismic risk profiles, incorrectly
judged to represent a higher risk (Type I errors). Limiting Type I errors to an acceptable level should
be a goal as long as the resulting greater Type II errors are not burdensome. Much of the following
discussion addresses how to limit the likelihood of an assessment reaching a technically indefensible
conclusion.
This discussion is intended to be considered for application to Building Stability, Site Stability and
Building Damageability, Building Contents Damageability and Business Interruption Assessments.
While much of the discussion focuses on building damage, it applies to all the assessment disciplines
by extension.
Practice E2557 in conjunction with Guide E2026, specify minimum requirements to achieve the
purpose of evaluating the seismic risk of a proposed real estate commitment. It requires determination
of the:
(A) Likelihood of site failure, that is whether faulting, landslides, or liquefaction can occur within
the site that can damage the building;
Discussion: One purpose is to limit investments to sites that will not fail, because often the local
jurisdictions may not allow reconstruction of buildings at failed site or the market value of the site may
be severely impaired in the future because of the site’s past failure. The second purpose is to assure
that if site failure occurs the damage is within acceptable bounds.
(B) Stability of the building at the Building Code specified levels;
Discussion: While damage repair can be a formidable cost, it is limited by the value of the property.
The settlements for death and injury of occupants caused by instability are bounded by net TOTAL
worth of the owner, not just the owner’s equity and particularly if the owner had prior reason to
suspect instability.
E2557 − 16a
(C) Financialriskintheselectedscenario;PML(probablemaximumloss)ofthebuildingorgroup
of buildings, where PMLmay be defined as the SEL(scenario expected loss) or SUL(scenario upper
loss) in the Design Basis Earthquake ground motion, or in other terms that are specific, such as
Probable Loss in the Maximum Capable Earthquake.
Discussion: The level of risk must be specified (for example, mean value, or 10 % chance in 50 years),
because if absolute certainty is desired, then every building can suffer a 100 % loss, even if highly
improbable. The science and technology of building construction and evaluation is not so
well-developed that absolute statements can be made.
X1.1 Site Failure the original design, often characterize the potential for lique-
faction at the site and the severity its effects, and recommend
X1.1.1 It is taken as intuitive that investments in structures
steps to mitigate such effects. In the absence of a site-specific
that are astride faults should warrant special consideration of
geotechnical report, more approximate means may be used. In
the acceptability of the building’s seismic performance.
the State of Washington, the Dept. of Natural Resources
Similarly, investments in properties with expected site failure
providesstatewidemapsforliquefactionsusceptibility[Palmer
due to liquefaction, landsliding, or faulting warrant careful
2004](2).Sincethe1990s,mosturbanareasinCaliforniahave
consideration of the implications of such failure. The issue of
been zoned to identify areas that require geotechnical investi-
significance becomes important, when it is noted that
gation for liquefaction in new construction, and new designs
seismically-induced liquefaction within a layer of supporting
are required to consider liquefaction by ASCE 7, but such
soils could occur, and yet the differential settlement over the
zonesindicateonlythepossiblepresence,butnotthedegree,of
building footprint does not result in significant loss to the
a liquefaction hazard. Other sources (USGS, ABAG, etc.)
building and which may be repaired. In other cases the design
produce maps presenting approximate degrees of susceptibility
may have adequately considered liquefaction and provided a
(for example, very low, low, moderate, high and very high)
foundation that is bearing below the level of site failure.
based on surface geology, depth to ground water and limited
Practice E2557 defines significant damage as damage exceed-
soil borings. Where liquefaction is expected for the scenario
ing 5 %, but this may be set according to the client’s needs.
ground motions in question, special care is needed in seismic
This leaves damageability as the essential open discriminant in
distinguishing an acceptable transaction from one that is not. risk assessment, and the involvement of a qualified geotechni-
cal engineer or engineering geologist should be considered.
X1.1.2 There are several available tools to evaluate faulting
hazard. Since 1972, California has regulations for the investi-
X1.1.4 There are several available tools to evaluate lands-
gation of surface fault rupture hazards, with formal zones
liding hazard. Most state and regional geological surveys have
established around faults deemed active and geologically well
mapped landslide hazards, including past slides, where the
defined [Special Publication 42] (1). Most other states have
natural slope and/or soil materials are prone to sliding, where
implemented at the state or local level, identification of active
related to seismic triggering or other causes. These provide a
faults and fault-zones. And the geological literature has iden-
means of identifying slopes whose debris slides could extend
tified and mapped most significant faults in all regions. User
intothepropertyunderconsideration,aswellasconditionsthat
guidelines may vary, but sites found within such zones in
warrant design consideration for the building. Slope instability
California need not be deemed unstable if the requisite
caused by liquefaction of the toe of an embankment, say at a
geotechnical investigations have been done and the reports are
creek or river, is termed lateral spreading and is normally part
available, and acceptable set-backs of the foundation from the
of the liquefaction assessment. Where landsliding is expected
nearest identified surface fault traces have been established.
for the scenario ground motions in question, special care is
Other states have somewhat less well-defined programs, and
needed in seismic risk assessment, including involvement of
thesurfacetracesoffaultsmaybeundefinedorundated.Where
knowledgeable professions in this discipline.
surface faulting hazards are known or suspected, the involve-
ment of a qualified geotechnical engineer or engineering
X1.2 Practice E2557 Application
geologist is recommended.
X1.2.1 Application of Practice E2557 requires that the User
X1.1.3 There are several available tools to evaluate soil
make a number of decisions on: setting the specific definition
liquefaction. Soil liquefaction may result in loss of bearing
of the statistical measures of damageability, requirements for
strength of soils supporting shallow foundations, differential
the assessor, the Level of Investigation, and selecting the
settlement on flat sites, tilting of buildings, lateral spread and
person or institution to do the assessment.The basic premise is
lurching, disruption of utility connections (causing loss of
to select the criteria to make investment or lending decisions in
power, water, gas, signal, or sewer), slope failures, flotation of
such a way as to make distinctions between seismically good
tanks and upheaval of basement slabs. The best source of
and bad buildings, and to do this in a manner that is reasoned,
information is a site-specific geotechnical investigation report,
measurably reliable, and sufficiently economical such that
or foundation report. Such reports, typically done as a part of
decisions can be made within the available resources, knowl-
edge and time for them to be made. The requirements for site
6 and buildings stability are well described and have few
The boldface numbers in parentheses refer to a list of references at the end of
this standard. discretionary variables except the choice of the Level of
E2557 − 16a
Investigation, which by Guide E2026 should be the same for X1.3.2 The SL and PL damageability measures are funda-
site and building stability and damageability assessment. mentallydifferent.SLpresentsthedamagestatisticsforagiven
scenario, say the 475-year return period acceleration, or the
X1.2.2 The two critical decisions for the User are: (1) what
average ground motion in a specified earthquake of given
damageability measure(s) is to be used to estimate the risk and,
magnitude on a specified fault. SL values have no explicit
(2) what level of uncertainty in the risk assessment can be
return period, (although the scenario earthquake may be
tolerated. From these the Level of the Investigation and the
associated with a return period for the ground motions). PL
selection of the assessor’s necessary qualifications follow.
values correspond to a specified return period for ground
After the assessment is presented, the Users must determine if
motions, but have no specific earthquake scenario event with
the report meets their requirements for decision making along
which the damage is associated. While the SL gives the
with the ASTM requirements. This latter issue is addressed in
damage associated with the defined scenario event alone, the
thevalidationdiscussionbelow.Withtheunderstandingofhow
PL gives a damage level associated with a likelihood of
to make decisions on these three issues, Practice E2557 reports
exceedancefromallearthquakesthatmayoccurinagiventime
can be used with some confidence in making financial deci-
period. SL has the advantage of being easy to understand,
sions and commitments.
while PL gives a better measure of the risk of damage over
time.
X1.3 Selecting the Damage Measure
X1.3.1 While Practice E2557 requires, at a minimum, X1.3.3 The most common SL measures are SEL and SUL.
reporting the SEL, it may be prudent to consider more than a Caution is suggested when using SULas a sole reported value,
singlemeasureoftheriskofaspecifiedpropertydamageability since for a single building the ratio of the SUL/SEL may be
value.This was a central point of the Black Swan, whereTaleb large, often in excess of 2.0, [Thiel, Kosonen, Stivers, 2012]
(3) argued that to do otherwise is to court disaster when the (4) and as noted in Fig. X1.1. For SL the commonly used
unexpected occurs that was not considered. The Guide E2026 scenarios are:
defined damage measures are: (1) A ground motion at the site with a 475-year return
(1) Scenario Loss (SL), which requires a decision about period at the site from a probabilistic ground motion hazard
what statistic to use, the SEL or SUL, or some other statistic, analysis. This in the past was designated the design basis
as well as the scenario event to be used, and earthquake (DBE).
(2) Probable Loss (PL) requires the return period for (2) The Maximum Capable Earthquake (MCE) on any
exceedance (PL ) for a given damage level, or the damage nearby fault.
N
level with a stated probability of exceedance in a given time (3) The maximum of the SLfor the DBE or other measures
period. of damageability appropriate to the user.
FIG. X1.1 Suggestions of Ranges for SUL/SEL Ratio for Single Building as a Function of Level of Investigation and SEL.
The User should inquire of the Provider the basis for damage values not within these ranges to verify that the methods
were technically appropriate.
E2557 − 16a
(4) Ground motion referenced in the design building code performer, these uncertainties are likely to be very large. Level
(for example, ASCE 7) or evaluation standard (for example, 3 should have the lowest uncertainty, with the intermediate
ASCE 41). levels progressively more certain in their results, with damage-
(5) Ground motions in specified earthquakes on specified ability uncertainly decreasing less rapidly than does stability
faults within the region. uncertainty. Guide E2026 for Levels 1 and higher provides for
minimum levels of expertise and experience forAssessors and
X1.3.4 The MCE used byASTM is defined differently than
defines two levels, Senior and Field Assessors, see 3.2.
itisinASCE7forapplicationinstructuraldesignapplications.
Here the MCE is characterized as the earthquake from among X1.4.2 Generally, for a portfolio seismic risk manager that
all those likely to impact the site that has the highest mean is evaluating the incremental seismic vulnerability of a group
ground acceleration. In ASCE 7 it is defined based upon of investments, the seismic risk screening process should lead
performance levels for structural design applications, which to a more seismically robust set of investment properties. The
may be a probabilistic or deterministic value, and is substan- seismic risk screening process is not foolproof (Type I and II
tially different. errorswilloccur),andunanticipatedearthquakelosseswillstill
occur, even with a good seismic risk screening process. But a
X1.3.5 The most common characteristics of the PL assess-
good process will reduce their occurrence compared to a no
ment are to define PL as:
screening process or a poorly executed process. A portfolio
(1) The damage level with a 475-year return period for
seismic risk manager should also seek to avoid localized
exceedance (PL475), equivalent to a 10 % probability of
accumulations of risk, where multiple buildings may be highly
exceedance in 50 years, or other stated time period
damaged in a single large earthquake.
(2) The damage level with a 10 % probability of excee-
dance in the nominal term [WG1] of the commitment, or other
X1.5 Uncertainty Reflected in Risk Estimates
term required by the User.
X1.5.1 Seismic risk for a building is reported is commonly
X1.3.6 Note that for regular application, Practice
presented as scenario loss (SL), with scenario expected loss
E2557 6.5.2.2 suggests reporting of several of these damage
(SEL) representing the mean or expected value of loss, and
measures, not just one. The setting of due diligence criteria,
scenario upper loss (SUL) representing the loss that has a 10 %
includingthedamagemeasure,theLevelsofInvestigation,and
percent probability of exceedance due to the specified ground
setting criteria for acceptance of a building as an acceptable
motion of the scenario considered. Earthquake loss estimates
seismic risk, are discussed in [Thiel, 2001] (5).
should reflect the Level of Investigation in the Building
X1.3.7 Both the SUL and PL are expressed in terms of
Damageability (BD) assessment as affected by the site hazard
probability statements. These values need to be supported by
characterization, construction documents reviewed, field sur-
calculations based on the mathematical concepts of probability
vey and engineering investigation conducted. Fig. X1.1 pro-
and statistics. For example, to find the SUL as the 90 % upper
vides rough guidance to allow the User to gauge whether the
confidence level of the damage ratio requires that a reasonably
ratio SUL/SEL for an individual building adequately reflects
applicable probability distribution function be employed for
the level of uncertainty from the information considered and
the damage ratio. Also, for a group of buildings at one site,
the investigation accomplished, for a scenario with a specified
while the replacement value weighted SEL values for the
hazard level on a stable site. Note that site instability will
buildings may be added, based on the rule that the mean value
increase the level of uncertainty relative to those shown. It can
of a sum is equal to the sum of the means of the individual
be used as an evaluative tool for examining the reliability of a
components, this addition cannot be done for the SUL or PL
draft or final PML report by comparing the ratio SUL/SEL to
values since the standard deviation of a sum of random
the graphed ratios. If an SUL is not reported, then the report
variables is the square root of the sum of the squares of the
has not met the requirements of Practice E2557. When doing
individual standard deviations along with any covariance
this evaluation, be careful to review whether the Level of the
effects due possible non-independent response behavior of the
reportwasconsistentwithworkrequiredbythestandard.Ifthe
buildings. Many Providers incorrectly assert that the SULfor a
ratioislessthanthelowerthresholdofFig.X1.1,thentheUser
group of buildings is the average of the SUL values for the
should request a justification for the conclusion. Similarly, if it
individual buildings. This is not mathematically correct. De-
is higher than the upper bound of the range, then the User
termining other statistics on damageability for groups of
should request justification. If the reasoning for these conclu-
buildings, whether SL or PL values, have to be performed
sions is not clear, then it may be prudent to request a peer
correctly; only for SEL is the adding approach correct.
review of the report by a knowledgeable engineer. For groups
ofbuildings,theproblemsaremorecomplex.See,forexample,
X1.4 Selecting the Acceptable Uncertainty Level
Thiel [2001] (5) for some of the issues posed in computations
for multiple buildings.
X1.4.1 Guide E2026 specifies four Levels of Investigation,
ranging from Level 0, which has only reporting requirements,
X1.6 Management of Uncertainties
to Level 3, which is an extensive investigation and analysis of
the building.The higher the Level, the more expense and effort X1.6.1 There are several ways to control uncertainty of the
required to complete such a study. A Level 0 report has the assessments conclusions in the Practice E2557 process:
highest uncertainty in its results for both stability and (1) The User should set clear criteria for conducting
damageability, and noting the lack of requirement for the seismic risk assessments, and then screen and select Providers
E2557 − 16a
(engineering consultants) to meet the qualifications set in likely seismic performance of the retrofit such that a technical
Practice E2557 and Guide E2026, as well as the User’s own reviewer or design professional can understand the work to be
done, its basis, and the reasons that the retrofit will mitigate the
requirements.
(2) The User should set the Level of Investigation high defects identified and yield adequate performance.
enough to assure that the assessment is competently and
X1.7 Other General Guidance
completely done consistent with the User’s needs. It is cau-
X1.7.1 The ASTM Committee has the following additional
tioned that a Level 0 assessment in Guide E2026 has almost no
specific observations that warrant consideration:
requirements except for reporting, and thereby is has the
(1) The value of having accurate and current structural
highest risk of both Type II and Type I errors. Level 0 may be
documents available for the review cannot be understated; also
a good starting point for a decision process that can accom-
of value are architectural drawings, soil and foundation inves-
modate the possibility of further investigation at a higher level,
tigation reports, and if possible structural calculations, along
say for property acquisition that will be held for the long term.
with field inspection and testing reports. The absence of these
Appendix X2 provides some additional guidance on setting
documents requires significantly more effort on the part of the
levels based on risk tolerance levels or property values.
assessor to reach a comparable certainty in the results com-
(3) The User should retain individuals that have reliable
pared to when they are available. The drawings should include
qualifications and experience to perform the study. Practice
boththebuildingasconstructed,andasstructurallymodifiedto
E2557 states that Level 1 or higher assessments should be
the present, whether by repair, extension or modifications.
completed by Level 1 qualified Providers, with no require-
Geotechnical investigation reports (“soils reports”) are also
ments for Level 0. Level 0 Investigations are considered to
important, particular where community hazard maps call atten-
provide the highest uncertainty of results of any investigation.
tion to potential site failure hazards for the site. Often when an
Some moderation of the uncertainty in Level 0 Investigations
owner does not have the structural design information or a
can be achieved by requiring the person(s) performing the
geotechnical report, the local building jurisdiction has such
assessment to be a licensed professional with qualifications for
records; when they do not, they may have other records (for
an Guide E2026 Level 1 investigation, rather than the minimal
example, the original building permit) with the names of the
requirements for a Level 0 investigation. This is to assure that
architect, and structural and geotechnical engineers, who may
the person making the judgments based on minimal informa-
have these records.
tiononthebuildinghavetheexperiencetomakesuch.Theless
(2) Some buildings have been seismically retrofitted. Cau-
time and energy expended the more demand for expertise.
tion is necessary when the basis for a retrofit was limited in
(4) The User or Provider should make a strong effort to
scope, rather than comprehensive. Some retrofits may be
locate structural drawings. If the assessor does not have access
undertaken as “prudent owner” actions, to address a deficiency
to the structural design and/or structural modification drawings
identified in a structural review. In such cases, the retrofit may
of the existing building or other records of the original
be permitted by the building jurisdiction so long as the retrofit
construction and how it has been structurally modified, and has
is deemed to reduce the seismic vulnerability of the building.
not visited the building, then it is unlikely that reliable
Other retrofits may be required by local ordinance. In each
conclusions can be made of the building’s expected seismic
case, the requirements for which the retrofit was designed and
performance, even if the assessor is highly qualified and
the areas of work are critical to ascertain. The applicability of
knowledgeable. A site visit alone is sometimes insufficient to
the requirement may be limited, for example, many unrein-
draw reliable conclusions even by very well-qualified review-
forced masonry bearing wall buildings are reported as retrofit-
ers. Generally the architectural elements mask the structural
ted based on meeting community requirements for bracing
system and its character and quality are hard to reliably
parapets, with no other work done to correct floor and roof
determine by just visual observation. If the building is particu-
diaphragm connections to the heavy masonry walls, or other
larly simple structurally and its structural elements can be
major vulnerabilities. The basis for such community require-
viewed from the interior and exterior reliable conclusions may
ments was not to protect the occupants, but to protect the
be possible. In concrete and masonry elements, even when
people near the building on walkways. In other cases the
structural elements are exposed, important detailing of rein-
community or client requirements of the retrofit could be
forcement is not visible. The result is that for most structural
limited to achieving stability improvements, but may not meet
types where the connection and construction details cannot be
ASCE 41 performance standards, and they may be limited in
viewed, lack of access to design drawings can limit the
scope. If an assessment report does not indicate that the retrofit
conclusions of an assessment to high uncertainty.
design basis and permitted design documents have not been
(5) Guide E2026 defines the qualifications of Senior and reviewed, and there is no conformation in the field that the
Field Assessors in 3.2 and 6.2.3, and recommends that the
work was completed, then it is advisable to consider the report
investigatorsforLevel1andhighermeettheserequirements.It to be highly uncertain. Many buildings have retrofit work that
may be prudent for a User to consider such as a minimum
was permitted and with plans that were approved, but for
qualificationforallinvestigationswheretheUserhasaconcern whatever reason the retrofit was not implemented.
to have a high confidence in the results of an assessment.
(3) Where the assessor has not visited the building, and
(6) If the report includes a recommendation for seismic relies on photographs taken by others, the uncertainty in the
retrofit to meet the Users requirements, the report should results should be assessed as very high, even if the reviewer is
provide enough detail of the proposed modifications and the qualified at the Senior or Field Assessor level. Even when the
E2557 − 16a
assessor has the structural design drawings and a geotechnical differentbuildingtypesandregionsarecontainedwithinASCE
report, the uncertainly may still be significant, although lower, 41. The benchmark code and years vary based on the building
since the structure may have been altered since construction.
type and building region. A building constructed after its
(4) A reasonable (but not sufficient) qualification for the benchmark year is expected to have better performance than
assessor is to be a professional engineer licensed to perform
one constructed before, and may be comparable for stability to
structural work, or a licensed architect. Subsection 6.3 of the
those designed to the current applicable code.
reference Guide E2026 provides a number of qualification
(6) When a seismic resisting system is or was novel or
issues that are not limited just to a license.An assessor having
unique at the time of construction, care should be taken to
done many assessments may or may not have adequate
assure that the assessor is adequately experienced to under-
knowledge of the science and engineering issues necessary to
stand its expected performance. This is not to say that they are
understand to do seismic assessments. Note that there are
more dangerous, but early in the development of any new
several branches of Civil Engineering (all of which use the
structural system there is more uncertainty in the quality and
term Professional Engineer), such as environmental, geotech-
effectiveness of the system, warranting higher qualifications
nical and transportation that would not themselves give the
for the assessor, and sometimes requiring structural engineer-
assessor proper qualifications to perform a structural reviews
ing analysis, to limit the uncertainty in the resulting estimates
consistent with those given in 6.3 of Guide E2026. The User
to levels that are accepted for other well-established systems.
should confirm that the person doing the assessment has the
(7) Until recently, the separation of buildings to avoid
knowledge and experience to complete the assignment for that
collision during earthquakes was not a building code require-
particular building type consistent with Guide E2026.Itis
ment. While referenced as an issue in prior editions, it was not
often useful to review several reports the assessor has prepared
until 1985 edition of the Uniform Building Code (UBC) that a
to discover how thorough the assessment is, the degree to
method to calculate the separation was provided. As a
which they provide evidence of technical understanding of the
consequence, seismic separations for buildings designed prior
building(s) reviewed, and to assess whether they have met the
to about 1990 are often inadequate to prevent contact and
stated requirements of ASTM and the client’s needs for
pounding under the ground motions commonly considered for
reliability and uncertainty control. Seismic evaluation is a
studies under Guide E2026. The separation that is adequate
highly technical and demanding application of structural engi-
depends in part on the structural system and geometry of the
neering that requires experience and expertise not shared by all
adjacent building. Structural stability and damageability as-
structural engineers or architects.
sessments should be considered deficient if they do not address
(5) Conformance with the applicable building code at the
the adequacy of building separations and their consequences.
time of construction should reduce, but will not eliminate,
Similarly, the possibility of falling parapets, or closure walls,
damage in an earthquake. The historic purpose of the building
such as from adjacent unreinforced masonry structures, should
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E2557 − 16 E2557 − 16a An American National Standard
Standard Practice for
Probable Maximum Loss (PML) Evaluations for Earthquake
1,2
Due-Diligence Assessments
This standard is issued under the fixed designation E2557; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice establishes standard-of-care for evaluation and classification of the financial risks from earthquake damage to
real estate improvements for use in financial mortgage transactions and capital investment evaluation. As such, this practice permits
a user to satisfy, in part, their real estate transaction due-diligence requirements with respect to assessing and characterizing a
property’s potential losses from earthquakes. This practice is intended to address only physical damage to the property from site
and building response.
1.1.1 Hazards addressed in this practice include earthquake ground shaking, earthquake-caused site instability, including
faulting, subsidence, settlement landslides and soil liquefaction, earthquake-caused tsunamis and seiches, and earthquake-caused
flooding from dam or dike failures.
1.1.2 Earthquake-caused fires and toxic materials releases are not hazards considered in this practice.
1.1.3 This practice does not purport to provide for the preservation of life safety, or prevention of building damage associated
with its use, or both.
1.1.3.1 This practice does not address requirements of any federal, state, or local laws and regulations of building construction
or maintenance. Users are cautioned that current federal, state, and local laws and regulations may differ from those in effect at
the times of construction or modification of the building(s), or both.
1.1.3.2 This practice does not address the contractual and legal obligations between prior and subsequent Users of seismic risk
assessment reports or between providers who prepared the report and those who would like to use such prior reports.
1.1.3.3 This practice does not address the contractual and legal obligations between a provider and a user, and other parties, if
any.
1.1.4 It is the responsibility of the owner of the building(s) to establish appropriate life-safety and damage prevention practices
and determine the applicability of current regulatory limitations prior to use.
1.2 Considerations not included in the scope: the impacts of damage to contents, loss of income(s), rents, or other economic
benefits of use of the property, or from legal judgments, fire sprinkler water-induced damage or fire.
1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and are not considered standard.
2. Referenced Documents
2.1 ASTM Standards:
E2026 Guide for Seismic Risk Assessment of Buildings
2.2 Other Standards:
UBC-97 Uniform Building Code, 1997 Edition
IBC International Building Code, current edition
This practice is under the jurisdiction of ASTM Committee E06 on Performance of Buildings and is the direct responsibility of Subcommittee E06.25 on Whole Buildings
and Facilities.
Current edition approved Jan. 1, 2016May 15, 2016. Published June 2016. Originally approved in 2007. Last previous edition approved in 20072016 as E2557-07.-16.
DOI: 10.1520/E2557-16.10.1520/E2557-16A.
Portions of this publication reproduce content from the 1997 Uniform Building Code, International Code Council, Inc., Falls Church, Virginia. Reproduced with
permission. All rights reserved.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from International Code Council (ICC), 500 New Jersey Ave., NW, 6th Floor, Washington, DC 20001, http://www.iccsafe.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2557 − 16a
2.3 ASCE Standards:
ASCE 7 Minimum Design Loads for Buildings and Other Structures, current edition
ASCE 41 Seismic Evaluation and Retrofit of Existing Buildings, current edition
3. Terminology
3.1 See also definitions in Guide E2026.
3.2 475-year site ground motions, n—seismic induced ground motions at a site with approximately: a return period of 475 years,
a 10 % probability of exceedance in 50 years, and an annual frequency of 0.21 %. Also referred to as the DBE.
3.3 field assessor, n—field assessor, as defined in Guide E2026.
3.4 independent reviewer, n—independent reviewer, as defined in Guide E2026.
3.5 lateral load-resisting system, n—lateral load-resisting system, as defined in Guide E2026.
3.6 MCE, n—Maximum Capable Earthquake, as defined in Guide E2026.
3.7 probable loss (PL), n—probable loss, as defined in Guide E2026.
Available from American Society of Civil Engineers (ASCE), 1801 Alexander Bell Dr., Reston, VA 20191, http://www.asce.org.
3.7.1 Discussion—
When there are multiple buildings in the seismic risk assessment, then the damageability values for the group of buildings is to
be determined as specified in Guide E2026.
3.8 probable maximum loss (PML), n—probable maximum loss, as defined in Guide E2026.
3.9 provider, n—provider, as defined in Guide E2026.
3.10 scenario expected loss (SEL), n—scenario expected loss, as defined in Guide E2026.
3.10.1 Discussion—
When there are multiple buildings in the assessment then the SEL for the group of buildings is to be determined as specified in
Guide E2026, Section 5.3.
3.11 scenario loss (SL), n—scenario loss, as defined in Guide E2026.
3.11.1 Discussion—
When multiple buildings are in the seismic risk assessment, then the SL for the group of buildings is to be determined as specified
in Guide E2026, Section 5.3.
3.12 scenario upper loss (SUL), n—scenario upper loss, as defined in Guide E2026.
3.12.1 Discussion—
When there are multiple buildings in the assessment then the SUL for the group of buildings is to be determined as specified in
Guide E2026, Section 5.3.
3.13 SEL475, n—the scenario expected loss due to the occurrence of 10 %/50-year site ground motions.
3.14 SEL , n—the scenario expected loss due to the occurrence of MCE site ground motions.
MCE
3.15 senior assessor, n—senior assessor, as defined in Guide E2026.
3.16 significant damage, n—significant damage, as defined in Guide E2026
3.17 SUL475, n—the scenario upper loss due to the occurrence of 10 %/50-year site ground motions.
3.18 SUL , n—the scenario upper loss due to the occurrence of MCE site ground motions.
MCE
4. Summary of Practice
4.1 The objectives of this practice are as follows:
4.1.1 To synthesize and document good commercial practice for the determination and rating of seismic risk for buildings.
4.1.2 To facilitate standardization of earthquake risk evaluation terminology for financial transactions.
4.1.3 To establish an industry standard for the requirements to evaluate the financial risk for real estate.
E2557 − 16a
5. Significance and Use
5.1 This practice is intended for use as a voluntary standard by parties who wish to undertake the seismic risk assessment of
properties. The goal is for users to objectively and reliably compare the financial risks of earthquake damage to buildings, or groups
of buildings, on a consistent basis.
5.2 This practice is designed to provide requirements for the evaluation of earthquake damage risk so that technical reports
prepared for the evaluation and rating of seismic risk of a building(s) will be adequate for use by other entities. Potential users
including, but are not be limited to, those making equity investments, lending, and financial transactions, including securitized
mortgage lending by mortgage originators, loan servicers, underwriters, rating agencies, and purchasers of bonds secured by the
real estate.
5.3 The use of this practice may permit a user to satisfy, in part, their requirements for due diligence in assessing a property’s
potential for losses associated with earthquakes for real estate transactions.
6. Due-Diligence Investigation
6.1 The site stability, building stability and building damageability of the property shall be assessed.
6.2 The user shall specify the condition of the property to be evaluated. The seismic performance can be evaluated for the
property in its current condition, or as changed by proposed modification of the seismic response of the soils supporting the
building or a proposed seismically retrofitted condition of the building(s) or its sections, or any combination of these conditions.
6.2.1 The proposed seismic modifications of the site must be sufficiently described to allow evaluation of the modifications by
an Independent Reviewer.
6.2.2 The proposed seismic modifications of the building systems must be sufficiently described to allow evaluation of the
modifications by an Independent Reviewer.
6.3 The Guide E2026 level of investigation shall be specified by the user. The same level of investigation should be performed
for each type of the seismic risk assessment. Appendix X1X2 gives guidance on the setting of the level of investigation.
6.4 The qualifications of the Provider shall be specified as required for the level of investigation specified in 6.3 of Guide E2026.
The qualifications level must be equal to or higher than the corresponding level specified in 6.2 and 6.3. Appendix X1 gives further
guidance on the setting of minimum qualifications.
6.4.1 For an assessment of Level 1 or higher, the qualifications of Senior Assessor and the Field Assessor of the property and
its buildings shall be those of Guide E2026 Sections 6.2.3.2 and 6.2.3.3.
6.4.2 Notwithstanding the asserted level of investigation of a report, if the Senior Assessor or the Field Assessor, or both, do
not demonstrate the qualifications of Guide E2026 Section 6.2.3.2 and 6.2.3.3, then the report shall be designated a Level 0 report.
6.5 Seismic Risk Assessment Report—The findings shall be reported in conformance to the requirements of Guide E2026 for the
level of investigation specified by the user in 6.3 and by a provider qualified in accordance with the requirements of 6.4, with the
following sections:
6.5.1 A summary that contains the conclusions of the seismic risk assessment:
6.5.1.1 Location of the building(s), characterization of the site and site soils, and gravity and lateral load-resisting systems.
6.5.1.2 Stability determination of each building site under consideration when subjected to the seismic loadings for the building
site location and building characteristics as set forth in Section 9 of Guide E2026. Site stability determination need only be
qualitative in nature for an SS0 investigation. For SS1 investigations the site stability is a qualitative assessment that includes the
implications on damage to the building structural elements. For SS2 and SS3 investigations the site should be considered unstable
if significant damage is caused to the building by the site instability.
6.5.1.3 Stability determination of each building under consideration in the seismic loadings for the building site location and
building characteristics and for the level of investigation specified, as set forth in Section 8 of Guide E2026.
6.5.1.4 The building damageability values for the building or group of buildings as a whole for the level of investigation
specified as set forth in Section 10 of Guide E2026.
(1) PML shall be user-defined. At a minimum, the SEL and SUL shall be reported.
DBE DBE
NOTE 1—CMBS industry is currently defining PML as SEL . It is advisable that SEL and SUL values also be reported for MCE events in areas of
DBE
low and moderate seismicity areas where MCE poses significantly higher risk than the DBE.
6.5.1.5 A specification of the level of investigation for each assessment and a review of the methods used and the personnel
engaged.
6.5.1.6 Results for each of the conditions described in 6.2 that apply.
6.5.1.7 Appropriate reliance language for the report and signature. For Level 1 or higher investigations, the professional seal
of the provider.
6.5.1.8 All deletions and deviations from this practice (if any) shall be listed individually and in detail.
6.5.1.9 The report conclusion shall include the following statement: “We have performed a probable maximum loss (PML)
evaluation for earthquake due diligence assessment in conformance with the scope and limitations of Guide E2026 and Practice
E2557 for a Level XX (specify) assessment of [insert address or legal description], the property. Any exceptions to, or deletions
E2557 − 16a
from, this practice are described in Section [ ] of this report. This probable maximum loss (PML) evaluation for earthquake due
diligence assessment has determined the PML to be [ ]%.” PML is defined as [fill in the definition used]. The project [meets/does
not meet] the building stability and [meets/does not meet] the site stability requirements.
6.5.1.10 Each report should include a completed Appendix X2X4.
6.5.1.11 Each report should include a completed Appendix X3X5.
6.5.2 A body of the report that provides:
6.5.2.1 All detailed reporting information required by Guide E2026, Section 13, including the basis and background for the
work performed in support of the conclusions presented in the report.
6.5.2.2 PML values for each building, and, if appropriate, for the group of buildings.
(1) Report of any other information required by the user, which may include business interruption, and contents damageability.
(2) The organization that commissioned the report and the professional liability limitations of the report provider shall be
disclosed in the report.
6.5.3 Attachments and appendices to the report as appropriate including detailed resumes of the Senior Assessor and the Field
Assessor that demonstrate their qualifications to perform this work as stated in this Practice.
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APPENDIXES
(Nonmandatory Information)
X1. GUIDANCE FOR USE OF E2557
INTRODUCTION
This Appendix provides guidance to decision makers for sorting their way through the intricacies
of seismic risk assessment. Usually a due-diligence financial decision is posed as should the
transaction be considered further or not? A PML assessment is commissioned to understand if there
is a seismic hazard at the property and the extent of the risk it poses. The process used to complete
PML assessments should consider the various sources of uncertainty as well as the financial and other
consequences that may arise when a good building is called ‘bad’ (Type I error), or when a bad
building is called ‘good’ (Type II error). An error of the first type precludes a possibly profitable
investment but otherwise is benign in that it does not lead to a loss, whereas the latter error has a higher
risk than is nominally acceptable and may lead to large loss. Type II errors lead to unexpectedly higher
risks and should be minimized consistent with other objectives of the User. Experience of the ASTM
Committee members suggests that the likelihood of Type II errors is highest in (1) Level 0 reports, (2)
reports issued by individuals that are not sufficiently knowledgeable and experienced at any level, and
(3) reports where the structural documents were not reviewed. If the result of the assessment is
unacceptable to the risk profile of the User and the economics of the deal are still attractive, then the
determination can only be made to pursue more, better quality and more reliable information and
assurance of qualified performers for the specific property. The goal should be to reach conclusions
that give reasonable control of Type II errors, but are not so risk adverse as to reject investments that
would be prudent and profitable that otherwise have acceptable seismic risk profiles, incorrectly
judged to represent a higher risk (Type I errors). Limiting Type I errors to an acceptable level should
be a goal as long as the resulting greater Type II errors are not burdensome. Much of the following
discussion addresses how to limit the likelihood of an assessment reaching a technically indefensible
conclusion.
This discussion is intended to be considered for application to Building Stability, Site Stability and
Building Damageability, Building Contents Damageability and Business Interruption Assessments.
While much of the discussion focuses on building damage, it applies to all the assessment disciplines
by extension.
Practice E2557 in conjunction with Guide E2026, specify minimum requirements to achieve the
purpose of evaluating the seismic risk of a proposed real estate commitment. It requires determination
of the:
(A) Likelihood of site failure, that is whether faulting, landslides, or liquefaction can occur within
the site that can damage the building;
Discussion: One purpose is to limit investments to sites that will not fail, because often the local
jurisdictions may not allow reconstruction of buildings at failed site or the market value of the site may
be severely impaired in the future because of the site’s past failure. The second purpose is to assure
that if site failure occurs the damage is within acceptable bounds.
(B) Stability of the building at the Building Code specified levels;
Discussion: While damage repair can be a formidable cost, it is limited by the value of the property.
The settlements for death and injury of occupants caused by instability are bounded by net TOTAL
worth of the owner, not just the owner’s equity and particularly if the owner had prior reason to
suspect instability.
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(C) Financial risk in the selected scenario; PML (probable maximum loss) of the building or group
of buildings, where PML may be defined as the SEL (scenario expected loss) or SUL (scenario upper
loss) in the Design Basis Earthquake ground motion, or in other terms that are specific, such as
Probable Loss in the Maximum Capable Earthquake.
Discussion: The level of risk must be specified (for example, mean value, or 10 % chance in 50 years),
because if absolute certainty is desired, then every building can suffer a 100 % loss, even if highly
improbable. The science and technology of building construction and evaluation is not so
well-developed that absolute statements can be made.
X1.1 Site Failure
X1.1.1 It is taken as intuitive that investments in structures that are astride faults should warrant special consideration of the
acceptability of the building’s seismic performance. Similarly, investments in properties with expected site failure due to
liquefaction, landsliding, or faulting warrant careful consideration of the implications of such failure. The issue of significance
becomes important, when it is noted that seismically-induced liquefaction within a layer of supporting soils could occur, and yet
the differential settlement over the building footprint does not result in significant loss to the building and which may be repaired.
In other cases the design may have adequately considered liquefaction and provided a foundation that is bearing below the level
of site failure. Practice E2557 defines significant damage as damage exceeding 5 %, but this may be set according to the client’s
needs. This leaves damageability as the essential open discriminant in distinguishing an acceptable transaction from one that is not.
X1.1.2 There are several available tools to evaluate faulting hazard. Since 1972, California has regulations for the investigation
of surface fault rupture hazards, with formal zones established around faults deemed active and geologically well defined [Special
Publication 42] (1). Most other states have implemented at the state or local level, identification of active faults and fault-zones.
And the geological literature has identified and mapped most significant faults in all regions. User guidelines may vary, but sites
found within such zones in California need not be deemed unstable if the requisite geotechnical investigations have been done and
the reports are available, and acceptable set-backs of the foundation from the nearest identified surface fault traces have been
established. Other states have somewhat less well-defined programs, and the surface traces of faults may be undefined or undated.
Where surface faulting hazards are known or suspected, the involvement of a qualified geotechnical engineer or engineering
geologist is recommended.
X1.1.3 There are several available tools to evaluate soil liquefaction. Soil liquefaction may result in loss of bearing strength of
soils supporting shallow foundations, differential settlement on flat sites, tilting of buildings, lateral spread and lurching, disruption
of utility connections (causing loss of power, water, gas, signal, or sewer), slope failures, flotation of tanks and upheaval of
basement slabs. The best source of information is a site-specific geotechnical investigation report, or foundation report. Such
reports, typically done as a part of the original design, often characterize the potential for liquefaction at the site and the severity
its effects, and recommend steps to mitigate such effects. In the absence of a site-specific geotechnical report, more approximate
means may be used. In the State of Washington, the Dept. of Natural Resources provides statewide maps for liquefaction
susceptibility [Palmer 2004] (2). Since the 1990s, most urban areas in California have been zoned to identify areas that require
geotechnical investigation for liquefaction in new construction, and new designs are required to consider liquefaction by ASCE
7, but such zones indicate only the possible presence, but not the degree, of a liquefaction hazard. Other sources (USGS, ABAG,
etc.) produce maps presenting approximate degrees of susceptibility (for example, very low, low, moderate, high and very high)
based on surface geology, depth to ground water and limited soil borings. Where liquefaction is expected for the scenario ground
motions in question, special care is needed in seismic risk assessment, and the involvement of a qualified geotechnical engineer
or engineering geologist should be considered.
X1.1.4 There are several available tools to evaluate landsliding hazard. Most state and regional geological surveys have mapped
landslide hazards, including past slides, where the natural slope and/or soil materials are prone to sliding, where related to seismic
triggering or other causes. These provide a means of identifying slopes whose debris slides could extend into the property under
consideration, as well as conditions that warrant design consideration for the building. Slope instability caused by liquefaction of
the toe of an embankment, say at a creek or river, is termed lateral spreading and is normally part of the liquefaction assessment.
Where landsliding is expected for the scenario ground motions in question, special care is needed in seismic risk assessment,
including involvement of knowledgeable professions in this discipline.
The boldface numbers in parentheses refer to a list of references at the end of this standard.
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X1.2 Practice E2557 Application
X1.2.1 Application of Practice E2557 requires that the User make a number of decisions on: setting the specific definition of the
statistical measures of damageability, requirements for the assessor, the Level of Investigation, and selecting the person or
institution to do the assessment. The basic premise is to select the criteria to make investment or lending decisions in such a way
as to make distinctions between seismically good and bad buildings, and to do this in a manner that is reasoned, measurably
reliable, and sufficiently economical such that decisions can be made within the available resources, knowledge and time for them
to be made. The requirements for site and buildings stability are well described and have few discretionary variables except the
choice of the Level of Investigation, which by Guide E2026 should be the same for site and building stability and damageability
assessment.
X1.2.2 The two critical decisions for the User are: (1) what damageability measure(s) is to be used to estimate the risk and, (2)
what level of uncertainty in the risk assessment can be tolerated. From these the Level of the Investigation and the selection of
the assessor’s necessary qualifications follow. After the assessment is presented, the Users must determine if the report meets their
requirements for decision making along with the ASTM requirements. This latter issue is addressed in the validation discussion
below. With the understanding of how to make decisions on these three issues, Practice E2557 reports can be used with some
confidence in making financial decisions and commitments.
X1.3 Selecting the Damage Measure
X1.3.1 While Practice E2557 requires, at a minimum, reporting the SEL, it may be prudent to consider more than a single measure
of the risk of a specified property damageability value. This was a central point of the Black Swan, where Taleb (3) argued that
to do otherwise is to court disaster when the unexpected occurs that was not considered. The Guide E2026 defined damage
measures are:
(1) Scenario Loss (SL), which requires a decision about what statistic to use, the SEL or SUL, or some other statistic, as well
as the scenario event to be used, and
(2) Probable Loss (PL) requires the return period for exceedance (PL ) for a given damage level, or the damage level with a
N
stated probability of exceedance in a given time period.
X1.3.2 The SL and PL damageability measures are fundamentally different. SL presents the damage statistics for a given scenario,
say the 475-year return period acceleration, or the average ground motion in a specified earthquake of given magnitude on a
specified fault. SL values have no explicit return period, (although the scenario earthquake may be associated with a return period
for the ground motions). PL values correspond to a specified return period for ground motions, but have no specific earthquake
scenario event with which the damage is associated. While the SL gives the damage associated with the defined scenario event
alone, the PL gives a damage level associated with a likelihood of exceedance from all earthquakes that may occur in a given time
period. SL has the advantage of being easy to understand, while PL gives a better measure of the risk of damage over time.
X1.3.3 The most common SL measures are SEL and SUL. Caution is suggested when using SUL as a sole reported value, since
for a single building the ratio of the SUL/SEL may be large, often in excess of 2.0, [Thiel, Kosonen, Stivers, 2012] (4) and as noted
in Fig. X1.1. For SL the commonly used scenarios are:
(1) A ground motion at the site with a 475-year return period at the site from a probabilistic ground motion hazard analysis.
This in the past was designated the design basis earthquake (DBE).
(2) The Maximum Capable Earthquake (MCE) on any nearby fault.
(3) The maximum of the SL for the DBE or other measures of damageability appropriate to the user.
(4) Ground motion referenced in the design building code (for example, ASCE 7) or evaluation standard (for example, ASCE
41).
(5) Ground motions in specified earthquakes on specified faults within the region.
X1.3.4 The MCE used by ASTM is defined differently than it is in ASCE 7 for application in structural design applications. Here
the MCE is characterized as the earthquake from among all those likely to impact the site that has the highest mean ground
acceleration. In ASCE 7 it is defined based upon performance levels for structural design applications, which may be a probabilistic
or deterministic value, and is substantially different.
X1.3.5 The most common characteristics of the PL assessment are to define PL as:
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FIG. X1.1 Suggestions of Ranges for SUL/SEL Ratio for Single Building as a Function of Level of Investigation and SEL.
The User should inquire of the Provider the basis for damage values not within these ranges to verify that the methods
were technically appropriate.
(1) The damage level with a 475-year return period for exceedance (PL475), equivalent to a 10 % probability of exceedance
in 50 years, or other stated time period
(2) The damage level with a 10 % probability of exceedance in the nominal term [WG1] of the commitment, or other term
required by the User.
X1.3.6 Note that for regular application, Practice E2557 6.5.2.2 suggests reporting of several of these damage measures, not just
one. The setting of due diligence criteria, including the damage measure, the Levels of Investigation, and setting criteria for
acceptance of a building as an acceptable seismic risk, are discussed in [Thiel, 2001] (5).
X1.3.7 Both the SUL and PL are expressed in terms of probability statements. These values need to be supported by calculations
based on the mathematical concepts of probability and statistics. For example, to find the SUL as the 90 % upper confidence level
of the damage ratio requires that a reasonably applicable probability distribution function be employed for the damage ratio. Also,
for a group of buildings at one site, while the replacement value weighted SEL values for the buildings may be added, based on
the rule that the mean value of a sum is equal to the sum of the means of the individual components, this addition cannot be done
for the SUL or PL values since the standard deviation of a sum of random variables is the square root of the sum of the squares
of the individual standard deviations along with any covariance effects due possible non-independent response behavior of the
buildings. Many Providers incorrectly assert that the SUL for a group of buildings is the average of the SUL values for the
individual buildings. This is not mathematically correct. Determining other statistics on damageability for groups of buildings,
whether SL or PL values, have to be performed correctly; only for SEL is the adding approach correct.
X1.4 Selecting the Acceptable Uncertainty Level
X1.4.1 Guide E2026 specifies four Levels of Investigation, ranging from Level 0, which has only reporting requirements, to Level
3, which is an extensive investigation and analysis of the building. The higher the Level, the more expense and effort required to
complete such a study. A Level 0 report has the highest uncertainty in its results for both stability and damageability, and noting
the lack of requirement for the performer, these uncertainties are likely to be very large. Level 3 should have the lowest uncertainty,
with the intermediate levels progressively more certain in their results, with damageability uncertainly decreasing less rapidly than
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does stability uncertainty. Guide E2026 for Levels 1 and higher provides for minimum levels of expertise and experience for
Assessors and defines two levels, Senior and Field Assessors, see 3.2.
X1.4.2 Generally, for a portfolio seismic risk manager that is evaluating the incremental seismic vulnerability of a group of
investments, the seismic risk screening process should lead to a more seismically robust set of investment properties. The seismic
risk screening process is not foolproof (Type I and II errors will occur), and unanticipated earthquake losses will still occur, even
with a good seismic risk screening process. But a good process will reduce their occurrence compared to a no screening process
or a poorly executed process. A portfolio seismic risk manager should also seek to avoid localized accumulations of risk, where
multiple buildings may be highly damaged in a single large earthquake.
X1.5 Uncertainty Reflected in Risk Estimates
X1.5.1 Seismic risk for a building is reported is commonly presented as scenario loss (SL), with scenario expected loss (SEL)
representing the mean or expected value of loss, and scenario upper loss (SUL) representing the loss that has a 10 % percent
probability of exceedance due to the specified ground motion of the scenario considered. Earthquake loss estimates should reflect
the Level of Investigation in the Building Damageability (BD) assessment as affected by the site hazard characterization,
construction documents reviewed, field survey and engineering investigation conducted. Fig. X1.1 provides rough guidance to
allow the User to gauge whether the ratio SUL/SEL for an individual building adequately reflects the level of uncertainty from the
information considered and the investigation accomplished, for a scenario with a specified hazard level on a stable site. Note that
site instability will increase the level of uncertainty relative to those shown. It can be used as an evaluative tool for examining the
reliability of a draft or final PML report by comparing the ratio SUL/SEL to the graphed ratios. If an SUL is not reported, then
the report has not met the requirements of Practice E2557. When doing this evaluation, be careful to review whether the Level of
the report was consistent with work required by the standard. If the ratio is less than the lower threshold of Fig. X1.1, then the
User should request a justification for the conclusion. Similarly, if it is higher than the upper bound of the range, then the User
should request justification. If the reasoning for these conclusions is not clear, then it may be prudent to request a peer review of
the report by a knowledgeable engineer. For groups of buildings, the problems are more complex. See, for example, Thiel [2001]
(5) for some of the issues posed in computations for multiple buildings.
X1.6 Management of Uncertainties
X1.6.1 There are several ways to control uncertainty of the assessments conclusions in the Practice E2557 process:
(1) The User should set clear criteria for conducting seismic risk assessments, and then screen and select Providers
(engineering consultants) to meet the qualifications set in Practice E2557 and Guide E2026, as well as the User’s own
requirements.
(2) The User should set the Level of Investigation high enough to assure that the assessment is competently and completely
done consistent with the User’s needs. It is cautioned that a Level 0 assessment in Guide E2026 has almost no requirements except
for reporting, and thereby is has the highest risk of both Type II and Type I errors. Level 0 may be a good starting point for a
decision process that can accommodate the possibility of further investigation at a higher level, say for property acquisition that
will be held for the long term. Appendix X2 provides some additional guidance on setting levels based on risk tolerance levels
or property values.
(3) The User should retain individuals that have reliable qualifications and experience to perform the study. Practice E2557
states that Level 1 or higher assessments should be completed by Level 1 qualified Providers, with no requirements for Level 0.
Level 0 Investigations are considered to provide the highest uncertainty of results of any investigation. Some moderation of the
uncertainty in Level 0 Investigations can be achieved by requiring the person(s) performing the assessment to be a licensed
professional with qualifications for an Guide E2026 Level 1 investigation, rather than the minimal requirements for a Level 0
investigation. This is to assure that the person making the judgments based on minimal information on the building have the
experience to make such. The less time and energy expended the more demand for expertise.
(4) The User or Provider should make a strong effort to locate structural drawings. If the assessor does not have access to the
structural design and/or structural modification drawings of the existing building or other records of the original construction and
how it has been structurally modified, and has not visited the building, then it is unlikely that reliable conclusions can be made
of the building’s expected seismic performance, even if the assessor is highly qualified and knowledgeable. A site visit alone is
sometimes insufficient to draw reliable conclusions even by very well-qualified reviewers. Generally the architectural elements
mask the structural system and its character and quality are hard to reliably determine by just visual observation. If the building
is particularly simple structurally and its structural elements can be viewed from the interior and exterior reliable conclusions may
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be possible. In concrete and masonry elements, even when structural elements are exposed, important detailing of reinforcement
is not visible. The result is that for most structural types where the connection and construction details cannot be viewed, lack of
access to design drawings can limit the conclusions of an assessment to high uncertainty.
(5) Guide E2026 defines the qualifications of Senior and Field Assessors in 3.2 and 6.2.3, and recommends that the
investigators for Level 1 and higher meet these requirements. It may be prudent for a User to consider such as a minimum
qualification for all investigations where the User has a concern to have a high confidence in the results of an assessment.
(6) If the report includes a recommendation for seismic retrofit to meet the Users requirements, the report should provide
enough detail of the proposed modifications and the likely seismic performance of the retrofit such that a technical reviewer or
design professional can understand the work to be done, its basis, and the reasons that the retrofit will mitigate the defects identified
and yield adequate performance.
X1.7 Other General Guidance
X1.7.1 The ASTM Committee has the following additional specific observations that warrant consideration:
(1) The value of having accurate and current structural documents available for the review cannot be understated; also of value
are architectural drawings, soil and foundation investigation reports, and if possible structural calculations, along with field
inspection and testing reports. The absence of these documents requires significantly more effort on the part of the assessor to reach
a comparable certainty in the results compared to when they are available. The drawings should include both the building as
constructed, and as structurally modified to the present, whether by repair, extension or modifications. Geotechnical investigation
reports (“soils reports”) are also important, particular where community hazard maps call attention to potential site failure hazards
for the site. Often when an owner does not have the structural design information or a geotechnical report, the local building
jurisdiction has such records; when they do not, they may have other records (for example, the original building permit) with the
names of the architect, and structural and geotechnical engineers, who may have these records.
(2) Some buildings have been seismically retrofitted. Caution is necessary when the basis for a retrofit was limited in scope,
rather than comprehensive. Some retrofits may be undertaken as “prudent owner” actions, to address a deficiency identified in a
structural review. In such cases, the retrofit may be permitted by the building jurisdiction so long as the retrofit is deemed to reduce
the seismic vulnerability of the building. Other retrofits may be required by local ordinance. In each case, the requirements for
which the retrofit was designed and the areas of work are critical to ascertain. The applicability of the requirement may be limited,
for example, many unreinforced masonry bearing wall buildings are reported as retrofitted based on meeting community
requirements for bracing parapets, with no other work done to correct floor and roof diaphragm connections to the heavy masonry
walls, or other major vulnerabilities. The basis for such community requirements was not to protect the occupants, but to protect
the people near the building on walkways. In other cases the community or client requirements of the retrofit could be limited to
achieving stability improvements, but may not meet ASCE 41 performance standards, and they may be limited in scope. If an
assessment report does not indicate that the retrofit design basis and permitted design documents have not been reviewed, and there
is no conformation in the field that the work was completed, then it is advisable to consider the report to be highly uncertain. Many
buildings have retrofit work that was permitted and with plans that were approved, but for whatever reason the retrofit was not
implemented.
(3) Where the assessor has not visited the building, and relies on photographs taken by others, the uncertainty in the results
should be assessed as very high, even if the reviewer is qualified at the Senior or Field Assessor level. Even when the assessor has
the structural design drawings and a geotechnical report, the uncertainly may still be significant, although lower, since the structure
may have been altered since construction.
(4) A reasonable (but not sufficient) qualification for the assessor is to be a professional engineer licensed to perform structural
work, or a licensed architect. Subsection 6.3 of the reference Guide E2026 provides a number of qualification issues that are not
limited just to a license. An assessor having done many assessments may or may not have adequate knowledge of the science and
engineering issues necessary to understand to do seismic assessments. Note that there are several branches of Civil Engineering
(all of which use the term Professional Engineer), such as environmental, geotechnical and transportation that would not
themselves give the assessor proper qualifications to perform a structural reviews consistent with those given in 6.3 of Guide
E2026. The User should confirm that the person doing the assessment has the knowledge and experience to complete the
assignment for that particular building type consistent with Guide E2026. It is often useful to review several reports the assessor
has prepared to discover how thorough the assessment is, the degree to which they provide evidence of technical understanding
of the building(s) reviewed, and to assess whether they have met the stated requirements of ASTM and the client’s needs for
reliability and uncertainty control. Seismic evaluation is a highly technical and demanding application of structural engineering that
requires experience and expertise not shared by all structural engineers or architects.
(5) Conformance with the applicable building code at the time of construction should reduce, but will not eliminate, damage
in an earthquake. The historic purpose of the building code is to provide a reasonable likelihood of life safety for the occupants
of the buildings when various natural events, including earthquakes, occur. It is not generally intended to limit damage to any
particular level, except for some special purposes like acute-care hospital regulation, but helps achieve this purpose by limiting
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catastrophic failure of building elements and systems, and requiring seismic bracing and anchorage of nonstructural elements.
Conformance with building codes that are evaluated as providing acceptable performance for the specific building type is an
effective, but not absolutely reliable, measure to limiting damage. Benchmark years for different building types and regions are
contained within ASCE 41. The benchmark code and years vary based on the building type and building region. A building
constructed after its benchmark year is expected to have better performance than one constructed before, and may be comparable
for stability to those designed to the current applicable code.
(6) When a seismic resisting system is or was novel or unique at the time of construction, care should be taken to assure that
the assessor is adequately experienced to understand its expected performance. This is not to say that they ar
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