This 660-ton pendulum protects Taiwan's tallest skyscraper from earthquakes

• A 660-ton steel sphere hangs between the 87th and 92nd floors of Taiwan's tallest building.
• The "tuned mass damper" can reduce the building's movements by up to 40%.

Taiwan's tallest skyscraper has a special device to protect it from earthquakes and high winds: a 660-ton steel pendulum that hangs over a thousand feet above the ground.

The Taipei 101 building — the tallest building in the world when it was completed in 2004 — stretches 101 stories tall, reaching a height of 1,667 feet, including its spire.

Its famous pendulum helped Taipei 101 survive the latest 7.4 magnitude earthquake to strike Taiwan on Wednesday morning.

Because of its location in one of the most active seismic and volcanic regions in the world along the Pacific Ring of Fire, the building needs to have some pretty heavy-duty defenses against earthquakes.

The skyscraper was designed by C.Y. Lee & Partners, a local architectural firm, to be flexible enough to withstand the earthquake tremors and typhoon winds that are common in Taiwan.

And the cherry on top of the building is a massive steel sphere called a tuned mass damper. It weighs 660 metric tons and has the power to reduce, or "dampen," the building's movements by up to 40%, according to the company, A+H Tuned Mass Dampers, that helped create the device.

At about 18 feet in diameter, the tuned mass damper is constructed of 41 layers, each nearly 5 inches thick, of solid steel plating that are welded together to form the golden sphere, Taipei 101 explains on its website. It hangs from 92 steel cables, each about 3.5 inches thick and 138 feet long, between the 87th and 92nd floors in the center of the building.

A "bumper ring" at its base helps limit the range of the ball's back-and-forth swing to about 59 inches during extreme typhoon-force winds and powerful earthquakes.

And although tuned mass dampers are present in other buildings around the world, like New York's Central Park Tower and Ireland's Spire of Dublin, what makes Taipei 101's unique is that viewers can watch it in action from an indoor public observatory.

Other buildings in Taiwan didn't fare as well as Taipei 101 on Wednesday.

More than 100 buildings were damaged throughout Taiwan, about half of which were in Hualien County, CNN reported.

Taiwanese authorities have said 70 people are trapped in rock quarries and over a hundred people are trapped in highway tunnels.

The quake killed at least nine people and injured more than 900 others, the Associated Press reported.