Almost all countries that have a coastline are connected to a subsea cable. There are over 100 cables damaged every year around the world. We list the types and causes of damage and how 70% of cable damage can be prevented.
As of early 2017 there are approximately 428 subsea cables in service around the world spanning over 1.1 million kilometres, carrying power and transmitting data from continent to continent. (source Telegeography).
Nearly all countries that have a coastline are connected to a subsea cable.
Depending on the location of the cables, they either rest on the ocean floor or are buried in the seabed.
Cables near the shore-end, in waters often less than 150 metres deep, are usually buried during installation to depths of 1-3 metres into the seabed, to protect them from damage by fishing, anchors and other causes.
However, subsea cables do break. Causing issues from minor outages to lowered internet speeds to a complete loss of connectivity which can be disastrous.
And more often than not, cables are damaged rather than broken, typically by ship anchors or a fishing trawler that snags the cable and damages it.
There are on average over 100 cable faults every year (source Telegeography Blog). Here are some types and causes of damage...
Shunt fault - this type of damage breaks the insulation and allows electrical power for repeaters to shunt to sea water. Shunt faults may leave fibres intact.
Fibre fault - these faults can disrupt communications.
Complete break - where electrical and fibre optic cables are completely severed or cut.
In water depths greater than 1,000 metres, faults are almost always caused by natural events such as current abrasion, underwater landslides and underwater seismic activity. In water depths of less then 200 metres faults are nearly always caused by man-made activities such as fishing and anchoring.
Around 70% of all cable faults are caused by fishing and anchoring activities (man-made) and around 12% are caused by natural hazards (current abrasion or earthquakes). The AssetMonitor service from UltraMAP can protect subsea cables from fishing and anchor damage saving clients millions of pounds in repair, loss of service and potential insurance costs.
Fishing activity from trawlers - Over a 3rd of all cable damage is caused by fishing activity. Trawling and fixed nets including stow nets cause damage. The East Asian region has high cable fault rates as stow nets are used intensively in the East China Sea. Their large anchors drag through the mud and damage cables. Pair trawling uses a net towed between two vessels which can snag cables resting on the seabed causing damage.
Damage from anchors - 25% of subsea cable damage arises from ship anchors. Large anchors of fishing vessels and merchant vessels cause cable damage. Anchoring outside designated areas causes damage. Dragging anchors in error during passage causes damage (recent fault records show that merchant ships sometimes do not fasten their anchors securely during short passages and these can cause cable damage).
Natural disasters and undersea landslides - 8% of damage is caused by the environment but can impact multiple cables. Most faults caused by seabed movement occur in deep water.
Current abrasion - Around 6% of cables are damaged through the current scraping cables against rocky surfaces.
Shark bites - Cable damage from shark attacks is exceedingly rare and often considered a myth. While it’s true that in the past sharks have bitten a few cables, they are not a major threat.
Other causes - Equipment failure is less common.
Intentional cable cut - In March 2013 naval forces arrested three men alleged to have attempted to cut an undersea cable off the coast of Alexandria. The head of Egypt Telecom said the incident caused a 60 percent drop in internet speeds.
Mistaken cable cut - In 2011 an entire country lost internet for five hours after a 75 year old woman sliced through a fibre-optic cable with her spade while scavenging for copper.
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