Radar images from Japan tsunami offer hope for new warning system

[News_Editor]

Radar images from Japan tsunami offer hope for new warning system

2011-08-18 05:37:33 GMT+7 (ICT)

LOS ANGELES (BNO NEWS) -- U.S. and Japanese scientists have for the first time ever observed a tsunami by high-frequency radar, raising the possibility of new early warning systems.

Parts of northeastern Japan were devastated in March when an enormous 9.0-magnitude earthquake struck off its coast, unleashing a giant tsunami. Scientists at the University of California in Davis (UC Davis) were able to identify the tsunami waves with the help of high-frequency radar.

Professor John Largier, an oceanographer at UC Davis, and his colleagues have been using a high-frequency radar array at the Bodega Marine Lab to study ocean currents for the last 10 years. The lab is part of a network of coastal radar sites funded by the State of California for oceanographic research.

Largier, together with collaborators from Hokkaido and Kyoto universities in Japan and San Francisco State University, used data from radar sites at Bodega Bay and Trinidad in California and two sites in Hokkaido, Japan, to look for the tsunami offshore.

The scientists found that the radar does not pick up the actual tsunami wave - which is small in height while out at sea - but changes in currents as the wave passes. The researchers found they could see the tsunami once it entered shallower coastal waters over the continental shelf. As the waves enter shallower water, they slow down, increase in height and decrease in wavelength until finally hitting the coast.

The continental shelf off the California coast is quite narrow, and approaches to the coast are already well-monitored by pressure gauges, Largier said. But he said radar detection could be useful, for example, on the U.S. East Coast or in Southeast Asia, where there are wide expanses of shallow seas. "It could be really useful in areas such as south-east Asia where there are huge areas of shallow continental shelf," Largier said.

The earthquake and tsunami in Japan killed at least 15,698 people while more than 4,600 people remain missing. The tsunami also killed two people in Indonesia and in California.

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