Communication cables laid on the sea bed will help in enhanced prediction of tsunamis

Syed Akbar

Hyderabad: Communication cables laid on the sea bed will help in enhanced prediction of tsunamis, scientists at the city-based National Geophysical Research Institute, and the University of Colorado, USA, have discovered.

Tsunamis, which are triggered by earthquakes, volcanic eruptions or even meteors hitting the seas, send electric signals through the ocean. The communication cables, both serving and discarded, on the sea bed are capable of picking up those electric signals. Moreover, the salty sea water around boosts these electric signals.

A simple monitoring of the undersea communication cables for any electric surge will aid in detection of tsunamis. The work was carried out by a team led by Dr Manoj Nair of University of Colorado and Dr T Harinarayana of NGRI. Scientists from the National Institute of Oceanography, Goa, and Swiss Federal Institute of Technology, Zurich, also participated in the research work.

"Vessels far out at sea may not notice the waves passing underneath at

the speed of a jetliner, because the wave heights are very small in the deep ocean. This makes their detection and monitoring a challenge. Tsunamis send electric signals through the ocean that appear to be sensed by the vast network of communication cables on the sea bed," Dr Manoj pointed out.

The researchers used computer models to estimate the size of an electric field created by the force of the 2004 Indian Ocean tsunami as it travelled over major submarine cables. It is estimated that the 2004 tsunami induced voltages of about 500 milli volts (mV) in the cables. This is very small compared to a 9-volt battery, but still large enough to be distinguished from  background noise on a magnetically quiet day.

"By monitoring voltages across this network of ocean cables, we may be able to enhance the current tsunami warning system," they said.

The movement of electrically conducting ocean water in the ambient geomagnetic field induces secondary electric and magnetic fields in the oceans. Ocean water transport is now routinely inferred from undersea cable voltage data.