Terrorism is defined by the Federal Bureau of Investigation (FBI) as “the unlawful use of force or violence against persons or property to intimidate or coerce a government, the civilian population, or any segment thereof, in furtherance of political or social objective”. 

Frequency – Due to the differing types of terrorism and the variety of terrorist, political, and social extremist groups that perpetuate these acts, the likelihood of any act of terrorism taking place in Washington State is believed to be a frequency of once every 1 to 10 years.  Note: Although terrorist or violent extremist attacks and plots have not occurred consistently within the past decade, the Northwest has encountered more than 20 attempted and successful attacks in the past decade; averaging out to two per year.

People – If a terrorist attack were to occur in a highly populated city in Washington, it can be expected that 1,000 to 10,000 people could potentially be impacted.  Note: This is based on a ‘worst case’ scenario, where an improvised explosive device (IED) is used in a large-scale attack similar to that of 9/11 or Mumbai.  A more likely case scenario would be an active shooter, in which less than 100 people would be impacted.  The actual numbers of people impacted by a terror event is dependent upon the terrorists’ motivation or desired outcome, tactic used, specific location, and weapon type.

Economy – Recent terrorist attacks in the U.S. have negatively affected the local economy of the cities in which they occurred.  If a terrorist attack were to occur in Washington State, a 1-2% gross domestic product (GDP) change would be an expected result.  Note: The psychosocial impacts would be a major effecting factor on the economy, in addition to the physical damage caused by a terror attack.  Psychosocial impacts, also known as the “fear factor”, can include: the populaces’ perceptions of local or regional stability, hesitation of going to large public gatherings, mistrust in law enforcement and government to deter terror events, and a general uneasiness in certain areas where an extremist attack has occurred.

Property – If a large-scale attack was to occur in a highly populated city or on a critical infrastructure in Washington State, the expected damage would likely be in excess of $1 billion.  Note: This is based on a ‘worst case scenario’, where an IED is involved.  A more likely case scenario would be an active shooter, in which less than $1 million of damages would occur.  The actual dollar amount incurred in any terror event is completely dependent upon the terrorists’ motivation or desired outcome, tactic used, specific location, and weapon type.

Previous Occurrences - Since 2001, there have been more than 20 terrorism and violent extremism cases in or with connections to the Northwest (Washington, Oregon, Idaho).  Once viewed as an external problem, the U.S. has been subjected to a growing number of homegrown and domestic terrorism events, making it more commonplace than ever before.  Though terrorism is not new, the vast number of methods in which an attack can occur has seemingly expanded due to an increased interest.  A plot can include multiple combinations of tactic type, weapon(s) type, location, target type, and number of operators.  Increased security measures over time have forced terrorist and violent extremists to become more innovative in their attempts to concoct the most effective and lethal combinations of attack components while maintaining the ability to go undetected until the time of the operation.

Probability of Future Events - Historically, terrorists and violent extremists have demonstrated their continued desire to commit acts of terrorism in highly populated or high profile areas.  Numerous critical infrastructures and public events have been the targets of foiled terror plots in Washington State, as well.  The map below displays the population densities of counties within Washington.  Highly populated counties tend to have a heavier infrastructure base to support a large population and, therefore, typically have more potential targets for terrorists and violent extremists seeking to inflict harm on these types of systems.  This is not to say that these are the only target-rich environments.  For example, intelligence reporting indicates terrorists’ interests in targeting infrastructure such as dams, food supplies, or cyber infrastructures; which can be located in sparsely populated areas or are not centralized to one specific locale.

Population Densities by County:

terrorism statimage1

Densities are based on April 2012 county population estimates from the Washington State Office of Financial Management.

 The Department of Homeland Security has identified 18 critical infrastructure and key resource (CIKR) sectors which covers the gamut of facilities, sites, routes, and systems which are most vulnerable to acts of violence, intrusion, or destruction.  Additionally, special events or sites attracting large gatherings tend to be the most lucrative targets due to the high volumes of potential victims, and become even more appealing during visits by high profile personalities and dignitaries.  Examples of high impact targets within the 18 CIKR sectors include:

  • Commercial buildings (stadiums, concert venues, convention centers, theatres, parks, shopping malls, casinos, etc.)
  • Cyber / Information Technology (system networks, power grids, communication industry, etc.)
  • Special events (parades, religious services, festivals, other planned celebrations, etc.)
  • Government (courthouses, schools, universities, hospitals, etc.)
  • Law Enforcement / Emergency Services (first responders and all law enforcement facilities, equipment, personnel, etc.)
  • Defense (military bases, facilities, airfields, equipment, personnel, national laboratories, etc.)
  • Transportation (airports, bridges, ferries, interstate highways, passenger rail, tunnels, seaports, hazardous materials pipelines, etc.)
  • Financial Institutions / Banks
  • Historical landmarks, monuments, museums, and other iconic sites
  • Dams, water reservoirs, and the power distribution network


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