Latest oceanic fiber-optic cable detects undersea quakes

July 7, 2008 (IDG News Service) The Japan Meteorological Agency (JMA) began laying a fiber-optic cable under the Pacific Ocean on Sunday, but it won't be used for telecommunications. The cable is part of an advanced monitoring and alert system that could provide warning should a destructive earthquake occur close to Japan.

Undersea earthquakes are particularly dangerous because they can start tsunamis, or tidal waves -- destructive waves that possess much more energy than normal waves. Japan has been hit by killer tsunami waves in the past, but the most famous series occurred in December 2004 following an earthquake off Indonesia. More than 225,000 people are estimated to have been killed in that tsunami's wake.

The new fiber cable extends 130 miles off the south coast of Japan near Shizuoka prefecture -- an area that has long been viewed by seismologists as having a significant chance of a major earthquake.

Along the cable are nine large pods, each about six feet long and 10 inches wide. The pods were developed by NEC Corp. as part of the project.

Five of the pods contain earthquake sensors, three have tsunami sensors, and the final one handles signal relay from the far end of the cable back to shore. From the shore, the signals are sent to data processing centers in Tokyo and Osaka. The two cities are several hundred miles apart, so if one is affected by an earthquake, the other should keep running.

Data from the pods will be used to help better determine the location and size of undersea earthquakes and the chances of a tidal wave.

Japan is one of the most seismically active nations in the world and is hit by several earthquakes per day that are strong enough to be felt. As a result, it has a highly sophisticated earthquake-reporting system. Typically, the size and intensity of a quake is announced by the JMA and flashed over TV screens within two or three minutes of it occurring. An integral part of this reporting system is determining whether the danger of a tsunami exists.

A more recent innovation is an early warning system that seeks to provide notice seconds in advance of strong quakes. The system monitors the fast-moving but weak primary waves to quickly determine the approximate location and intensity of a quake and attempts to get out a warning in advance of the more destructive secondary waves.

Recently, the warning system provided about 13 seconds' warning of a strong quake to the 1 million residents of Sendai city in northern Japan. The warning system can't yet provide alerts fast enough to those very close to the epicenter, but it's still fairly new, having started operation last October.

Reprinted with permission from

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