Via the electrical impulses they generate

Jan 25, 2010 11:29 GMT  ·  By

Scientists at the US National Oceanic and Atmospheric Administration (NOAA) and the University of Colorado have recently discovered that the vast network of communication cables that can be found today on the ocean floor have the ability to detect the electrical signals generated by tsunamis. This is made possible by the fact that salty seawater is a good conductor of electrical impulses. It is also able to generate an electric field, as it moves through the geomagnetic field our planet generates. Using a computer model, the team managed to establish the intensity of the 2004 Indian Ocean tsunami, and determine that it might have been picked up by the underwater cable network, PhysOrg reports.

“We estimate that the 2004 tsunami induced voltages of about 500 millivolts (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,” Manoj Nair, an expert who holds a joint appointment at NOAA and the UC, explains. The expert also underlines the fact that major research is needed into methods of separating the electrical signals caused by tsunamis from those coming from the upper layers of the atmosphere, such as the ionosphere. This layer can induce 100mV of voltage into marine communication networks, Nair explains.

The thing about tsunamis is that they are very tricky to detect. They are caused by a variety of factors, ranging from earthquakes and underwater volcanic eruptions to landslides and meteorite impacts. They travel underwater for most of their journey to shore, which means that, even if they pass under a ship at sea, at very high speeds, they are seldom detected. Before finally reaching the ground, they stay at a low level, and only increase in size in shallower waters. Therefore, even monitoring them is a challenge. Deep-water buoys are placed at various locations, but their efficiency is moderate.

Details of the new work appear in the February issue of the scientific journal Earth, Planets and Space. Researchers from the National Institute of Oceanography, India, and the National Geophysical Research Institute, also from India, were involved in this study as well. NOAA is currently placing a lot of emphasis on detecting tsunamis before they hit US shorelines, and the new investigation may help it do so successfully.