World Trade Center and Pentagon Attacks of 9/11/2001 Sources

The purpose of this guide is to direct users to authoritative, multidisciplinary sources of information on the World Trade Center and Pentagon attacks of September 11, 2001.

Table of Contents

Authoritative Professional Web Portals

  • NIST Disaster and Failure Events Data Repository
  • This repository will ensure that data collected during and after a disaster or failure event, as well as data generated from related research, is organized and maintained to enable study, analysis and comparison with future severe disaster events. The repository includes data from NIST's six-year investigation of the collapses of three buildings at New York City's World Trade Center (WTC 1, 2 and 7) as a result of the terrorist attacks on Sept. 11, 2001. Now available are thousands of photos and videos collected during the investigation; computer simulations created to model aircraft impact damage, fire spread and structural design characteristics; and the complete set of technical reports that document the body of NIST's work. Headings include:
  • Federal Building and Fire Safety Investigation of the World Trade Center Disaster: Final Report of the National Construction Safety Team on the Collapses of the World Trade Center Tower
  • Design, Construction, and Maintenance of Structural and Life Safety Systems
  • Baseline Structural Performance and Aircraft Impact Damage Analysis of the World Trade Center Towers
  • Mechanical and Metallurgical Analysis of Structural Steel
  • Active Fire Protection Systems
  • Reconstruction of the Fires in the World Trade Center Towers
  • Structural Fire Response and Probable Collapse Sequence of the World Trade Center Towers
  • Occupant Behavior, Egress, and Emergency Communication
  • The Emergency Response Operations
  • Final Report on the Collapse of World Trade Center Building 7
  • ICivilEngineer: The Internet for Civil Engineers: WTC Coverage
  • Intended to improve access for civil engineering professionals and students to technical and engineering information on the Internet, the ICivilEngineer site collects and classifies such information for its Web site. The section on the World Trade Center is both extensive and comprehensive. Headings include:
  • Cause of Twin Towers Collapse
  • Aftermath
  • Cleanup
  • Rebuilding WTC
  • Background Information
  • Pentagon Building Damage
  • Debate on High rise Buildings
  • Image Gallery
  • Research Reports
  • Related Websites
  • Related Books
  • World Trade Center Posters
  • The World Trade Center and Pentagon Tragedy
  • Compiled by Professor Louis Geschwindner, Pennsylvania State University, this site includes an extensive selection of Web articles on the events of 9/11, each classified, dated and annotated by Geschwindner. Major headings include:
  • Analysis of Collapse
  • Building Condition around WTC Site
  • WTC Below Grade Condition
  • WTC Site Clean-up
  • Occupancy of the WTC
  • Structural Investigation Teams
  • Pentagon Site
  • First Hand Reports (from both the WTC and Pentagon)
  • Pictures
  • WTC Facts
  • Insurance Industry Response
  • Rumors Debunked
  • Personal Writings
  • Filling the Void: What Happens to the Site
  • Rebuilding
  • Patriotic Images
  • This site is a unique and rich source of information on the two events.


Engineering Aspects

  • Designing Buildings to Resist Earthquakes
  • This New York Times article discusses how the principles of earthquake resistant design can be applied to help mitigate the effects of terrorist attacks on buildings in the New York City area and is based on interviews conducted at the MCEER-sponsored meeting, "Workshop on Lessons from the World Trade Center Terrorist Attack: Management of Complex Civil Emergencies and Terrorism-Resistant Civil Engineering Design," conducted June 24-25, 2002, in New York City. Also discussed at some length is the probability of a major (M 6.0) earthquake occurring in Manhattan and the impact such an event would have. The potential effects are illustrated in an accompanying map. How new construction and renovations to existing buildings have been affected by the adoption of the New York City Seismic Code, Local Law 17, in 1995 is also discussed.
  • Engineering and Organizational Issues Related to the WTC Terrorist Attack
  • This report series presents MCEER's findings from an NSF-funded research project to collect perishable data in the aftermath of the WTC attack. The project aims to gain a better understanding of how resilience is achieved in physical, engineered systems, and in organizational systems. The reports listed below can be ordered from the MCEER Web site.
  • Overview of Damage to Buildings Near Ground Zero (MCEER-02-SP02), by Michel Bruneau, Andrew Whittaker and Andrei Reinhorn
  • Reconnaissance and Preliminary Assessment of a Damaged Building Near Ground Zero (MCEER-02-SP03), by Jeffrey Berman, Gordon Warn, Andrew Whittaker and Michel Bruneau
  • Emergency Response in the Wake of the World Trade Center Attack: The Remote Sensing Perspective (MCEER-02-SP05), by Charles K. Huyck and Beverley J. Adams
  • From the WTC Tragedy to the Development of Disaster Engineering for Landmark Buildings – An Extension of the Performance-based Earthquake Engineering Approach (MCEER-03-SP04), by George C. Lee, Vladimir Rzhevsky, Mai Tong, and Suwen Chen
  • The Pentagon Building Performance Report – ASCE
  • This report from the ASCE building performance study (BPS) team that investigated the structural performance of the Pentagon during and immediately following the 9/11 terrorist attack presents significant findings regarding structural resistance to progressive collapse. The seven-month study, conducted by specialists in structural, fire, and forensic engineering, analyzed the essential features of column response to the impact of the hijacked aircraft and examined the residual frame capacity and structural response to the fire. In addition to a review of information on the building structure and the crash loading, the report includes assessments of other studies. Observations comparing and contrasting the construction of the Pentagon to current standards are made where pertinent. Recommendations for future design and additional research complete the report. Numerous figures and color photographs are included.
  • Hard copies of the report are available from ASCE, 1801 Alexander Bell Drive, Reston, VA 20191-4400 (telephone: 800-548-2723 or 703-295-6210; fax: 703-295-6211; e-mail:; Web site:
  • Proceedings from the MCEER Workshop on Lessons from the World Trade Center Terrorist Attack: Management of Complex Civil Emergencies & Terrorism-Resistant Civil Engineering Design
  • This Proceedings contains print abstracts and presentations on CD-ROM from the Workshop on Lessons from the World Trade Center Terrorist Attack. The objective of this workshop was to bring together leaders from the earthquake engineering community, the blast engineering community, the social sciences, and the emergency response community, to identify possible linkages between earthquake-protection and terrorism-protection issues, and how groups focusing on these two different problems could potentially work together in order to achieve terrorism-resistant communities and enhance earthquake engineering practice. Furthermore, the workshop examined the management of complex civil emergencies and terrorism-resistant civil engineering design.
  • Structural Engineer Describes Collapse of the World Trade Center Towers
  • This article reports on the John A. Blume Distinguished Lecture, November, 29, 2001, in which Ron Hamburger speculates on vulnerabilities in the design of New York's World Trade Center (WTC), which may have contributed to the collapse of the WTC's two main towers and adjacent buildings. Hamburger also discusses the effects of fire, the highjackers' strategies, and how WTC vulnerabilities may affect future building design.
  • Why Did the World Trade Center Collapse? Science, Engineering, and Speculation
  • This report discusses what the authors believe are misconceptions concerning the cause of the World Trade Center collapse. The article reviews the overall design of the towers and presents a detailed discussion, employing simple quantitative analyses, of the effect of the airplane impacts, the role played by the ensuing fire, and the anatomy of the collapse. Some guidelines for improvements in future structures are also presented.
  • Why the Towers Fell: An Exclusive Investigation into the Collapse of the World Trade Center
  • This NOVA video follows a blue ribbon team of forensic engineers as they investigate why the World Trade Center (WTC) towers fell. Coverage includes interviews with survivors and rescue personnel who recount the buildings' last moments and their own harrowing experiences. Also featured are insights of leading structural engineers into what may have happened on September 11 and how the investigative team came to understand the WTC collapse. Other segments cover:
  • a detailed examination of the building's original design
  • combing scrap steel yards and Ground Zero for evidence
  • testing building materials
  • calculating the role of the jet fuel in the fire
  • estimating the speed of the aircraft and the damage to the building's core
  • analysis of the effectiveness of the escape and fire protection systems
  • World Trade Center Building Performance Study: Data Collections: Preliminary Observations, and Recommendations (FEMA 403)
  • This report was intended to examine the damage caused by terrorist attacks on the World Trade Center, September 11, 2001. It aims to collect data, develop an understanding of the response of each affected building, identify the causes of observed behavior, and identify studies that should be performed. The report discusses the immediate effects of the aircraft impacts on each tower, the spread of fires following the crashes, the fire-induced reduction of structural strength, and the mechanism that led to the collapse of each tower. Additionally, the performance of buildings in the immediate vicinity of the towers is examined to determine the effects of damage from falling debris and fires. Recommendations are presented for more detailed engineering studies, to complete the assessments and produce improved guidance and tools for building design and performance evaluation.
  • Produced by the Federal Insurance and Mitigation Administration, Federal Emergency Management Agency, May 2002, the report can also be ordered from the FEMA Document Distribution Center, PO Box 2012, 8231 Stayton Drive, Jessup, MD 20794-2012 (telephone: 1-800-480-2520; fax: 301-362-5335).
  • World Trade Center Disaster: Structural Engineers at Ground Zero
  • This document was developed to provide documentation for preparing a response plan that uses structural engineers after a major collapse or failure and is based on discussions with structural engineering teams that worked at Ground Zero, as well as the author's own opinions based on working at Ground Zero. Among the topics addressed are the operational hierarchy, equipment needs, the structural engineering team, and safety and legal issues.
  • World Trade Centre – New York: Some Engineering Aspects
  • Compiled by Tim Wilkinson, University of Sydney, Australia, this Web site contains general information about the WTC, its structural system, as well as discussion, photos, and diagrams illustrating how and why the Towers collapsed. Also included are links to additional information.


Legislation and Government

  • Annotated Bibliography of Government Documents Related to the Threat of Terrorism and the Attacks of September 11, 2001
  • Compiled by Kevin D. Motes (US Government Information Division, Oklahoma Department of Libraries), this bibliography focuses on US federal documents on terrorism and, specifically, on attacks on the World Trade Center and the Pentagon and the attacks' global ramifications. All documents are described with concise annotations and are available through the Federal Depository system. Many of these publications are also available on the Web. The materials are arranged under three broad headings:
  • Terrorism and the American Homeland
  • The International Context of Terrorism;
  • The War on Terrorism.
  • Individual bibliographies of note include "Emergency Preparedness" and "Infrastructure and Federal Facilities Security. "
  • Department of Homeland Security (DHS)
  • The Department of Homeland Security (DHS) Web site includes information on many aspects of the DHS, including DHS organization; emergencies and disasters; threats and protection; research and technology; travel and transportation; and immigration and borders.
  • Making the Nation Safer: The Role of Science and Technology in Countering Terrorism
  • Prepared under the auspices of the National Research Council (NRC), this report discusses various terrorist threats that face the US and draws conclusions about the current state of readiness , providing recommendations for improvement. Among these is the suggestion that the federal government utilize the nation's scientific and engineering strengths to respond to terrorist attacks more effectively.
  • The report can be viewed and ordered from the Web site above. It can also be ordered from the National Academy Press (telephone: 202-334-3313 or 800-624-6242)
  • Reporters can obtain a copy from the Office of News and Public Information, the National Academies, 2101 Constitution Avenue NW, Washington, DC 20418 (telephone: 202-334-2138; fax: 202-334-2158; e-mail:
  • NIST and the World Trade Center
  • In response to the WTC tragedy, the National Institute of Standards and Technology conducted a 3-year building and fire safety investigation to study the factors contributing to the probable cause (or causes) of post-impact collapse of the WTC Towers (WTC 1 and 2) and WTC 7; expanded its research in areas of high-priority need such as:
  • prevention of progressive collapse
  • fire resistance design and retrofit of structures
  • fire resistive coatings for structural steel
  • NIST's report reachs out to the building and fire safety communities to pave the way for timely, expedited considerations of recommendations stemming from the investigation.
  • The 9/11 Commission Report: Final Report of the National Commission on Terrorist Attacks Upon the United States
  • The bipartisan commission investigating the events leading up to the September 11 attacks, the attacks themselves, and the response of numerous involved government agencies released this, its final report, in July of 2004. While the examination of intelligence failures received significant attention, especially through highly publicized hearings, the report also looks at emergency management issues raised by the day's events. In the concluding chapters, the commission sets out its recommendations for governmental reorganization in order to better prepare against future terrorist threats.


Economic Aspects

  • One Year Later: The Fiscal Impact of 9/11 on New York City
  • Prepared by William C. Thompson, Jr., the Comptroller of New York City, and his colleagues, this 65-page report offers an intensive look into the short and long term economic impact of 9/11 on the city. Along with looking at the loss of human capital and potential as a result of these events, the report details the impact on the city's budget, cash balances, and the impact of the federal aid administered by the Federal Emergency Management Association (FEMA). The report contains many helpful tables, including those detailing the estimated loss in gross city product, the decline in property taxes, and the resulting impact on the city's pension expenses. One of the final sections also contains material on the economic stimulus package that is currently in place to aid in rebuilding the economic vitality of Lower Manhattan.
  • Review of Studies of the Economic Impact of the September 11, 2001, Terrorists Attacks on the World Trade Center
  • This 40-page document from the US General Accounting Office (GAO) identifies and assesses the studies of ten key reports from nine different organizations regarding the economic impact of the terrorist attacks on the World Trade Center buildings in New York City (NYC). The organizations included in this review are:
  • NYC Office of the Comptroller
  • NY Governor and State Division of the Budget
  • NYC Partnership and Chamber of Commerce
  • Fiscal Policy Institute
  • NY State Senate Finance Committee
  • Milken Institute
  • NY State Assembly Ways and Means Committee
  • NYC Independent Budget Office
  • Federal Reserve Bank of NY
  • This document explores the studies and estimations of each organization's report, and determines if they meet standard economic criteria for analyzing economic impacts. Overall, the review finds the study by the NYC Partnership provided "the most comprehensive estimate."
  • Review of the Estimates for the Impact of 9/11 on New York Tax Revenues
  • This nine-page report by the General Accounting Office (GAO) is a follow-up to the May, 2002, Review of Studies of the Economic Impact of the September 11, 2001, Terrorists Attacks on the World Trade Center above concerning the economic impact of the September 11th attacks on New York. This update goes a step beyond the earlier study, by reviewing the tax revenue loss estimates of the New York City Office of Management and Budget and the New York State Division of Budget. According to the report, tax revenue loss estimates for the 2002 fiscal year are 1.6 billion for the city of New York, and 1.6 billion for the state. The 2003 fiscal year estimates are 1.4 billion for the city. The report contains a summary, background information on last year's national economy, and brief comments by both New York budget offices.

Seismological Aspects


Design, Rebuilding and Reconstruction

  • America Rebuilds: A Year at Ground Zero
  • A companion site to the PBS television program of the same name, America Rebuilds is a rich resource detailing the cleanup and rebuilding efforts at ""Ground Zero," the WTC site, in the months following the towers' collapse. The site uses photographs, videos and text to tell a compelling, human story through details about flooded tunnels and mangled steel. Engineers are among the key players featured in "Ground Zero Profiles," short essays with quotes from the individuals themselves. The "Imagining the Future" section includes a discussion of proposed designs for rebuilding on the site.
  • Lower Manhattan Development Corporation
  • The Lower Manhattan Development Corporation (LMDC) is a partnership between New York City and the state of New York aimed at rebuilding and revitalizing lower Manhattan. Created in the aftermath of the September 11 attacks, the LMDC coordinates the efforts of public and private stakeholders in the redevelopment of the WTC site. Available on the LMDC Web site are materials pertaining to this redevelopment, which will include, among other features, the 1,776-foot tall Freedom Tower and the September 11th memorial, Reflecting Absence.
  • New York New Visions: A Coalition for Rebuilding Lower Manhattan
  • The New York New Visions Web site represents the collective response of 20 architecture, planning, and design organizations who set forth some of their proposals and suggestions for the rebuilding of Lower Manhattan in the wake of September 11th. The cornerstone of the site is a 55-page report released in February 2002, which details their initial planning proposal for the economic, physical, and social rebuilding of the area. Different sections of the report deal with the importance of design standards, the interconnectivity of the area with the rest of New York, and a section dealing with the difficult question of the public planning process involved.
  • Rebuilding the World Trade Center
  • This report, by the Construction Institute of the American Society of Civil Engineers (ASCE), urges consideration of social, economic, and infrastructure factors in the redevelopment of the World Trade Center site. Trends discussed include:
  • the decrease in New York office leases since September 11
  • green building designs
  • the impact of suburban sprawl on city traffic patterns
  • security issues
  • The report also explains how lower building designs could address emergency evacuation, traffic congestion, and security and economic concerns.


Response and Recovery

  • Beyond September 11th: An Account of Post-Disaster Research
  • This volume contains the findings, lessons, and recommendations of the post-September 11 disaster research gathered by grant-recipient researchers with support from the National Science Foundation. The collection of 20 selections takes a distinct view in the wake of the disaster on topics ranging from engineering to behavioral science. Specific chapter headings include:
  • issues in disaster response
  • the engineered environment - buildings and infrastructure
  • individual and collective behavior
  • private sector roles and activities
  • public policy and political context
  • This collaborative production includes numerous conclusions and recommendations for the improvement of public policy and disaster response based on the findings from these studies. This publication may be ordered for $25 from the Natural Hazards Research and Applications Information Center, University of Colorado, 482 UCB, Boulder, CO 80309-0482 (telephone: 303-492-6818; fax: 303-492-2151; e-mail: The report may be downloaded free from the Web site as well.
  • Federal Investigators Classify WTC Victims' Locations within Collapsed Buildings
  • These results, from a study by the National Institute of Standards and Technology (NIST), provide information on the human toll of the attack on the World Trade Center, indicating the locations (in which building, above or below impact, or on which flight, for example) of those who lost their lives in New York City on September 11. Also included and categorized by the organizations they worked for are victims who were first responders.


Advanced Technologies

  • Images of the World Trade Center Site Show Thermal Hot Spots on September 16 and 23, 2001
  • This report presents results of the National Aeronautics and Space Administration's (NASA's) Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) remote sensing data and interpretations that mapped the distribution and intensity of thermal hot spots in the WTC area on September 16 and 23.
  • Lending a Helping Hand: Using Remote Sensing to Support Response and Recovery Operations at the World Trade Center
  • This article provides an overview of the role played by remote sensing in providing timely data and information on the nature of the World Trade Center (WTC) site following the 9/11 attacks. The article describes in detail the various types of satellite imagery and aerial data that were collected, rapidly processed and disseminated under very short notice and in challenging circumstances. This information was largely intended to provide practical information for use by emergency response teams at the WTC site and to keep decision-makers informed on the nature and magnitude of the disaster during a time of substantial uncertainty.