Undersea telecommunications cables in and out of Japan seem to have mostly survived the devastating earthquake that struck the country on Friday.
There are 20 trans-Pacific and intra-Asia cable systems that land in Japan, according to research firm Telegeography. As of early Saturday in Japan, there were some press reports of damaged cables within Asia, but the effects on communications appear to have been limited.
Mainland Chinese carrier China Unicom said two or three cables between Japan and China may have been damaged but traffic was being routed around the breaks, and Taiwan-based Chunghwa Telecom said the APCN2 cable was damaged but communication had not been disrupted, according to a report on the Wall Street Journal's MarketWatch site.
APCN2 is a 19,000-kilometer (11,800-mile) cable that links China, Hong Kong, Japan, Malaysia, the Philippines, Singapore, South Korea and Taiwan, according to Telegeography. Its capacity is nearly 2T bps (bits per second.)
Japan historically has been the biggest hub for undersea cable systems in Asia, though there is an increasing number of lines going to other countries in the region, said Telegeography analyst Stephan Beckert.
"There's a complete cat's cradle of cables out there," Beckert said.
Earthquakes have damaged undersea cables in the past. Last year, a major quake and aftershocks in Taiwan damaged four cables in six places, knocking out service for parts of two days. In 2009, an earthquake in Taiwan and undersea landslides caused by a typhoon damaged cables to China, disrupting access to some websites. In both cases, carriers eventually were able to restore traffic by rerouting it. Service providers typically use capacity on more than one cable to prevent outages.
"There is, at this point, a good deal of resiliency in the international networks," Beckert said.