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Associated Press October 30, 2001

Technology alone may not find bin Laden's cave

by Al Grillo

SAN JOSE, Calif. (AP) - President Bush is vowing to smoke Osama bin Laden and his lieutenants out of caves, but detecting subterranean lairs is no small feat. Under ideal conditions, high-tech tools can reveal the location and structure of underground cavities by measuring subtle changes in the force of gravity, seismic waves and electrical resistance.

"It's a real easy job if you have a bunch of graduate students and you can walk around on the ground taking measurements," said Antony Fraser-Smith, a Stanford University geophysicist. Afghanistan today is hardly the place for such field trips. Meanwhile, almost all U.S. reconnaissance tools - including radar and communications interception devices - are built for detecting something. Caves are all about the absence of something.

During the Vietnam conflict, U.S. soldiers faced enemies adept at tunneling. One of the most successful detection techniques involved carefully observing entrances for smoke or body odor.

In the early 1990s, a tunnel apparently dug by North Korea was found hundreds of feet beneath the Demilitarized Zone. Seismic testing and radar confirmed the location.

Smugglers also move drugs through underground passages from Mexico into the United States. These have usually been discovered through tips, rather than technology.

In all those cases, however, the cave-detectors were people on the ground.

To be most effective, cavern-hunting in Afghanistan would require much the same - while likely employing methods originally designed by geologists to find pipes, oil deposits and earthquake faults.

A common technique for mapping the underground is to monitor seismic waves produced in earthquakes, intentional explosions or simply thumping the ground with a large sledgehammer.

But small explosions near a suspected hide-out would attract unwanted attention as well as produce results far from conclusive.

"Seismic techniques are not ideal at all for detecting a cavity in the ground because the seismic waves don't go through the cavity - they go around it," Fraser-Smith said. "You tend not to see it."

Ground-penetrating radar, which works like underwater sonar and has been used to find archaeological treasures, is most effective on flat surfaces and has limitations.

"It can't get to the depths that you would need," said Roy Greenfield, a geosciences professor at Pennsylvania State University.

In another technique, researchers measure very slight fluctuations in the pull of gravity, which changes with variations in the planet's mass.

"It will show you oil deposits. It will show you lots of structures in the ground," Fraser-Smith said. "But they're not so good at picking up the absence of something."

And though possible to perform from the air, the technique is far more conclusive done on land.

It's also possible to detect cavities by measuring how electrical currents change as they pass through the ground, said Mats Lagmanson, a geophysicist and president of Austin, Texas-based Advanced Geosciences.

"I can't really say our troops can use this in a battle situation," he said. "They could use it when things have calmed down," because of danger to those who would administer it.

The U.S. military may have other, secret technologies at its disposal. In the Gulf War, soldiers faced enemies in underground bunkers, which led to more research into detection and destruction techniques.

U.S. Defense analysts, meanwhile, scour high-resolution satellite images for telltale signs of underground life, such as smoke rising from an entrance and roads that seem to lead to nowhere. Infrared sensors also might spot the heat of cooking fires, electrical generators or people.

"The tough aspect is doing it quickly," said William C. Martel, professor of national security affairs at the Naval War College. "I think the consensus probably is that if you have sufficient time, you can find these things."

Afghanistan should be well-covered by spy satellites given its Cold War history, particularly after the Soviet invasion in 1979, said Tim Brown, senior associate at GlobalSecurity.org, a security issues think-tank. "The Afghan war was just a practice," Brown said of the conflict that ended with the Soviets' 1989 withdrawal. "There should be a wealth of data (and) imagery left behind."


Copyright 2001 The Associated Press.