Earthquake Proof Buildings

Technology designed to keep buildings from collapsing works essentially in two ways: By making buildings stronger, or by making them more flexible, so they sway and slide above the shaking ground rather than crumbling.The latter technology employs an idea called "base isolation."For about 30 years, engineers have constructed skyscrapers that float on systems of ball bearings, springs and padded cylinders. They don't sit directly on the ground, so they're protected from some earthquake shocks. In the event of a major earthquake, they sway up to a few feet. The buildings are surrounded by "moats," or buffer zones, so they don't swing into other structures."You actually take the foundation of building and you put it either on almost like springs or on a mechanism so it is allowed to move a little bit with the earthquake," said Armstrong of the building code council.Well-designed buildings with base-isolation systems ensure that no lives will be lost, no matter the strength of an earthquake, said Michael Constantinou, a professor of civil engineering at the University at Buffalo, State University of New York.More difficult than perfecting the technology, he said, is figuring out how large of an earthquake will hit a certain area.

Tectonics Plates

This theory is now called plate tectonics. The plates "float"on the asthenosphere, a layer of soft, molten rock, and are pushed about by convection currents rising up from the mantle below. The plates move just an inch or two each year. But that's enough to create enormous stress when two plates run into each other.

Timeline of Recent Earthquake ( TOP 10 )

Chile Earthquake May Have Shortened Days on Earth

The massive 8.8 earthquake that struck Chile may have changed the entire Earth's rotation and shortened the length of days on our planet, a NASA scientist said Monday.

The quake, the seventh strongest earthquake in recorded history, hit Chile Saturday and should have shortened the length of an Earth dayby 1.26 milliseconds, according to research scientist Richard Gross atNASA's Jet Propulsion Laboratory in Pasadena, Calif.

"Perhaps more impressive is how much the quake shifted Earth's axis," NASA officials said in a Monday update.

The computer model used by Gross and his colleagues to determine the effects of the Chile earthquake effect also found that it should have moved Earth's figure axis by about 3 inches (8 cm or 27 milliarcseconds).

The Earth's figure axis is not the same as its north-south axis, which it spins around once every day at a speed of about 1,000 mph (1,604 kph).

The figure axis is the axis around which the Earth's mass is balanced. It is offset from the Earth's north-south axis by about 33 feet (10 meters).