Arecibo Observatory undergoing emergency repairs after earthquake damage

The Arecibo radio telescope in Puerto Rico.

The NAIC Arecibo Observatory's 305 meter (1,000 ft) radio telescope is undergoing emergency repair after being damaged during a 6.4 magnitude earthquake on January 13, 2014.

A large cable that supports the telescope's receiver platform had "serious damage," according to Bob Kerr, the Director of the Arecibo Observatory.

Bob Kerr

"A protocol structural survey following the January 13 earthquake revealed serious damage to [a] short cable section, with apparent breach of several cable strands," Kerr told reporters.

"An experienced structural engineering firm was brought to assess the damage, and to consider repair options."

The earthquake's epicenter was located in the ocean about 60 kilometers (37 miles) northwest of Arecibo and was one of the largest to hit Puerto Rico in several years.

The quake caused some floor cracking in buildings and homes on the island, as well as power outages, but no major damages or injuries, officials said.

There were, however, at least 70 aftershocks with at least three of a magnitude 3.5 or greater.

The famous radio observatory is located near Puerto Rico's north coast, and opened in 1963. It was built inside a depression left by a sinkhole and is the largest curved focusing dish on Earth.

The dish's surface is made of thousands of perforated aluminum panels, each about 1 by 2 meters (3 by 6 feet), supported by a mesh of steel cables.

The receiver is on a 900-ton platform suspended 137 meters (450 feet) above the dish by 18 cables running from three reinforced concrete towers.

It was one of these 18 cables that was damaged, and this particular cable was actually a known potential problem.

Kerr said that during original construction of the telescope in 1962, one of the original platform suspension cables that was delivered to the observatory was too short, and another short cable section was "spliced" to provide sufficient reach to the platform.

"That cable segment and splice near the top of one of the telescope towers was consequently more rigid than the balance of the suspension system," Kerr said.

"When the earthquake shook the site, just after midnight on January 13, it is that short cable and splice that suffered damage."

The platform hangs above the Arecibo dish, supported by cables. 

Credit: Cornell University.

"You might say that our structural Achilles heel was exposed," Kerr added.

Inspectors from New York's Ammann & Whitney Bridge Construction, who have been inspecting the Arecibo observatory site since 1972, were brought in to access the situation.

Kerr said a relatively low-cost (less than $100,000) repair option was designed, and materials are now being procured to complete a repair that is expected to bring the telescope back into full service.