WASHINGTON, July 14, 2011 — The Defense Department’s U.S. Atomic Energy Detection System has monitored the planet for nuclear blasts since 1947, but its sensors also help to pinpoint and assess large natural disasters around the world.
|An Air Force technician performs depot repair of a seismometer. The instrument will be returned to service at one of 40 seismic stations around the globe to detect nuclear tests.
U.S. Air Force photo
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Since 1980, this state-of-the-art system, called USAEDS, has been the responsibility of the Air Force Technical Applications Center at Patrick Air Force Base, Fla.
AFTAC’s job is to make sure foreign nations adhere to three nuclear test-ban treaties that have been in force since the 1960s and 1970s and that prohibit nuclear testing in the atmosphere and some underground tests.
But the increasingly sophisticated tools the network uses in this effort also have more down-to-earth applications.
USAEDS has sensors on Global Positioning System and Defense Support System satellites that monitor space and Earth’s atmosphere for light flashes, radioactivity and other telltale signs of nuclear explosions.
The system’s hydroacoustic sensors are microphones that listen for nuclear explosions under the sea. Infrasound sensors measure changes in the atmosphere generated by very-low-frequency acoustic waves that can come from above-ground nuclear explosions.
As part of the system, a WC-135 aircraft flies to the sites of explosions and collects air that scientists on the ground analyze for radioactive particles and radioactive gases.
And the system’s 40 seismic stations around the world — using the same technology scientists use to measure earthquakes — monitor the planet for underground nuclear explosions.
“When nuclear testing was forced underground [in the 1970s], we had to switch over to more dependence on things like seismic sensors, and our seismic stations started to expand,” AFTAC chief scientist David O’Brien told American Forces Press Service.
“Our first station was in Turkey, probably in the late 1950s, probably close to where the then-Soviet Union was testing [nuclear devices],” O’Brien said. “As time went on and more and more testing was going on underground,” he added, “we started establishing more of our overseas sites.”
Because of AFTAC’s critical mission to detect and report nuclear blasts, system sensors conform to the highest technical standards and operate day and night, 365 days a year.
So if anything cataclysmic happens anywhere on Earth — a large earthquake, for example — the system knows about it.
“If it’s a very large earthquake, anything over about magnitude 6.0, we will notify the U.S. Geological Survey, which is responsible for participating in the International Tsunami Early Warning System, O’Brien said.
“This is not a nuclear explosion, this is an earthquake [but] it’s large and it could be causing a lot of damage so we will immediately let the USGS know,” O’Brien said.
“The USGS probably has detected it too,” he added, “but this augments their information as well.”
The USGS National Earthquake Information Center in Colorado has a domestic network of seismic stations called the Advanced National Seismic System, and it is part of an international system called the Global Seismographic Network.
USGS, the U.S. National Science Foundation and an organization called the Incorporated Research Institutions for Seismology formed the international system, which has more than 150 seismic stations around the world.
The Pacific Tsunami Warning Center in Hawaii, part of the U.S. National Oceanic and Atmospheric Administration, uses USGS seismic data and a range of sensors in oceans around the world to issue earthquake and tsunami warnings for Hawaii, American territories in the Pacific, 25 countries in the Pacific Ocean basin, and the Indian Ocean region.
But there’s a big difference between these dedicated disaster warning systems and AFTAC’s nuclear detection network.
“We install our systems in areas where there is very low seismic noise,” O’Brien said.
“The USGS may have their stations close to cities where there’s lots of vibration in the ground,” he said, or in areas like California or New Zealand that have lots of seismic activity.
“The USGS is really looking for big earthquakes,” the scientist added. “They don’t have the requirements that we do — to look for very, very small explosions” that may occur underground during a nuclear test.”
The U.S. Atomic Energy Detection System looks for sometimes-subtle indicators of an atomic explosion, he said.
“I can’t tell you how low we go,” he said, referring to the lowest-level magnitude the system can detect, “but we go very much lower than a disaster network might go.”
Unlike many disaster and research networks, USAEDS runs 24 hours a day, seven days a week, 365 days a year, he said.
“Data is continually coming in, in real time from all these worldwide sensors. We analyze data as soon as it comes into the building,” O’Brien said.
“Our responsibility is to provide immediate notification if an explosion occurs anywhere in the world,” he said.
Another network that, like the Defense Department, monitors for nuclear explosions but also detects natural disasters is the Comprehensive Test Ban Treaty Organization’s International Monitoring System.
The treaty opened for signature in 1996 and is signed by most countries in the world but not yet ratified by enough countries to put the treaty into force.
In the meantime, the treaty organization, headquartered in Vienna, Austria, is building a global network of sensors and other program elements that ultimately will help enforce the treaty.
AFTAC experts have advised the organization about building its 337-facility network, and both AFTAC and the United States contribute data to the system.
“The United States is part of the International Monitoring System,” O’Brien said.
“When we signed the treaty, which we have not ratified yet, we agreed to put stations on U.S. soil to participate in the system. That includes seismic and hydroacoustic stations,” he said.
“Some of the sites we have in our USAEDS network also contribute to the IMS, he added, “but not all.”
In foreign countries where USAEDS has established seismic sites, the United States has agreements with those countries, O’Brien explained.
“Each country can decide whether or not they want to contribute to the International Monitoring System” or any other seismic network, he said.
“We want the data, but whether they give it to somebody else or not, we don’t care,” O’Brien said, “although [sharing the data] certainly benefits the International Monitoring System. That’s a positive aspect.”
In May, after a 9.0 magnitude earthquake and tsunami affected hundreds of thousands of people and damaged the Fukushima Daichi power plant in Japan, USAEDS was pressed into service, the scientist said.
The system’s seismic stations “most certainly detected the earthquake and many aftershocks,” O’Brien said, and the system was recruited to support U.S. efforts in response to the Japanese nuclear reactor accident.
“We deployed our WC-135 aircraft to collect air over the ocean east of Japan to determine radioactivity levels there,” he said.
Also in May, radionuclide sensors that are part of the International Monitoring System picked up traces of radioactive particles and gases from the stricken power plant. So far, more than 35 radionuclide stations have provided information on the spread of radioactivity from the Fukushima accident.
In addition to its primary mission, USAEDS also contributes to a U.S. program established through the Department of Homeland Security after the Sept. 11 attacks on the World Trade Center and the Pentagon in 2001.
“One thing the [new] Department of Homeland Security had to address was the possibility that a terrorist could detonate a nuclear device in the United States,” O’Brien said.
The result, he said, was the National Technical Nuclear Forensics Program, an interagency effort that involves the departments of Homeland Security, Security, Energy and Justice — primarily the FBI — as well as the Defense Department and the intelligence community.
The team, O’Brien said, “would respond to a nuclear explosion in the United States for the purpose of trying to determine who did it. It’s called attribution.”
In that effort, he added, USAEDS would use its aircraft to sample radioactive debris.
“The Army would do ground sampling,” O’Brien said, “but because we have been doing analysis on radioactive debris for many years and have laboratories in the United States that support us, we would oversee all the analysis of radioactivity.”
Whether radioactivity is detected by the Department of Energy or AFTAC’s aircraft or the FBI, the scientist said, “we would be the single point for the nation to do analysis of that debris for the attribution process.”
U.S. Department of Defense
Office of the Assistant Secretary of Defense (Public Affairs)