
William Park of BBC reports that ninety-nine percent of the world’s digital communications rely on subsea cables. When they break, it could spell disaster for a whole country’s internet. How do you fix a fault at the bottom of the ocean? Park writes:
It was a little after 17:00 on 18 November 1929 when the ground began to shake. Just off the coast of Burin Peninsula, a finger-like protrusion on the south of Newfoundland, Canada, a 7.2 magnitude earthquake disturbed the evening’s peace. Residents noticed only a little damage at first – a few toppled chimney pots.
But out at sea, an unseen force was moving. By around 19:30, a 13m-high (43ft) tsunami made landfall on the Burin Peninsula. In total, 28 people lost their lives as a result of drowning or injuries caused by the wave. […]
Although the landslide was not noticed at the time, it left a tell-tale clue. In its way lay the latest in communication technology at the time: transatlantic subsea cables. And those cables broke. Twelve of them were snapped in a total of 28 places. Some of the 28 breaks happened almost synchronously with the earthquake. But the other 16 breaks happened over a much longer period, as the cables snapped one after the other in a kind of mysterious ripple pattern, from 59 minutes after the earthquake to 13 hours and 17 minutes later, and over 500km (311 miles) away from the epicentre. (Read more about the undersea rivers that threaten the world’s internet.) […]
If a fault is found, a repair ship is dispatched. “All these vessels are strategically placed around the world to be 10-12 days from base to port,” says Mick McGovern, deputy vice-president for marine operations at Alcatel Submarine Networks. “You have that time to work out where the fault is, load the cables [and the] repeater bodies” – which increase the strength of a signal as it travels along the cables. “In essence when you think how big the system is, it’s not long to wait,” he says.
While it took nine months to repair the last of the subsea cable damage caused by the 1929 Newfoundland earthquake, McGovern says a modern deep-water repair should take a week or two depending on the location and the weather. “When you think about the water depth and where it is, that’s not a bad solution.”[…]
However, many countries are served by multiple subsea cables, meaning one fault, or even multiple faults, might not be noticed by internet users, as the network can fall back on other cables in a crisis.
“This really points to why there’s a need for geographic diversity of cable routes,” adds Clare. “Particularly for small islands in places like the South Pacific that have tropical storms and earthquakes and volcanoes, they are particularly vulnerable, and with climate change, different areas are being affected in different ways.” […]
In those places, an option is to tell people where cables are, and to increase awareness, adds Clare: “It’s for everyone’s benefit that the internet keeps running.”
Read more here.