Turbidity Currents & Subsea Cable Outages: Current WACS Outage

A turbidity current is the likely culprit for the WACS trunk outage. The same holds true for the 2Africa Ivory Coast branch failure. The Taiwan earthquake of December 2006 is instructive in this regard. The 22 knocked out cables failed in sequence over the course of several hours. So the sheer force of the earthquake was not responsible. Instead, the seismic event caused sediment to begin moving down the undersea slope of Taiwan's continental shelf. This was not a gentle slope, but rather the steep sides of the Kaoping subsea canyon, which is 4 kilometers deep. As the chart shows, cables went dark in sequence radiating from the epicenter outward as this undersea tidal wave traveled down the sides of the subsea canyon. The turbidity current traveled at speeds ranging from 3.7 meters per second to 5.7 meters (roughly 20 kilometers per hour). The sequence of events suggests there were at least 2 and probably turbidity currents involved. 

It is probably not a coincidence that the Ivory Coast also has a major subsea canyon like Taiwan. Canyons provide the gravitational force necessary to accelerate these debris slides. Turbidity currents are generally triggered by earthquakes or torrential rains that lead wide rivers to dump immense amounts of sediment and debris into the open sea. What sustains them is a subsea canyon which serves as a funnel to focus the energy and accelerate it.

Diagram Showing Sequence of Cable Failures In the Aftermath of the 2006 Taiwan Earthquake


Chart Listing Cables and Time That Their Outage Began

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