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| Fig. 1: The aftermath of the 1995 Oklahoma City Bombing. (Courtesy of the DOD. Source: Wikimedia Commons) |
Before the September 11, 2001 attacks, the Oklahoma City Bombing in 1995 was the worst, most fatal terrorist attack on American soil. A rental truck filled with homemade explosives was detonated outside a federal building (see Fig. 1), killing 168 people, including 19 children, and injuring upwards of 500 more. The bomber, Timothy McVeigh, used what was a common industrial ingredient to blow up the Alfred P. Murrah Federal Building, causing mass terror, and eventually forcing legislation on the product. [1]
After the attack, it was discovered that the 4,800 pounds bomb was filled with a mixture of ammonium nitrate and fuel oil. Colloquially known as ANFO, ammonium nitrate fuel oil was commonly used in mining, quarrying, and road-building, but was also regarded as a potential volatile substance. The bombers exacerbated the explosion by placing metal cylinders within the explosive package, filling them with hydrogen and potentially acetylene. This addition was used to increase the potential fireball and burning power of the explosion.
According to officials who spoke to the Washington Post, a safety fuse measuring around eight feet was likely used to detonate the package, while a public release of two seismographs gave an indication to the strength of the blast. A seismogram record from 26km showed two low-frequency wave trains about 10 seconds apart, consistent with what you'd expect from a single impulsive energy source. [2]
In December, 2007, legislation was enacted to regulate the sale and transfer of ammonium nitrate, the main ingredient used in the Oklahoma City Bombing. The new regulation, known as 6 U.S. Code 488a, forced the sale and transfer of the substance to go through an ammonium nitrate facility, specifically to prevent the 'misappropriation or use of ammonium nitrate in an act of terrorist'.
The 1995 Oklahoma City bombing, to this day, marks one of the most tragic and devastating terrorist attacks on American soil. However, this attack simultaneously enlightened American authorities about to accessibility of ANFO, and how it may continue to threaten the safety of US citizens. As a result, legislation was passed, which dramatically reduced the accessibility of ammonium nitrate, and thus the likelihood that someone may attempt a similar act of terror.
© Isaac White. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] C. S. North et al., "Coping, Functioning, and Adjustment of Rescue Workers After the Oklahoma City Bombing," J. Trauma. Stress 15, 171 (2002).
[2] B. Pfefferbaum, "The Impact of the Oklahoma City Bombing on Children in the Community," Mil. Med. 166, Suppl. 2, 49, (2001).
