When scientists received data from the earthquake that caused December's devastating Indian Ocean tsunami, they analyzed it in roughly half a minute. Within 25 minutes of the initial tremor, residents in the tsunami's path could have been warned. They were not.
Chinese geophysicist Ni Sidao, in a telephone interview with Xinhua, explained how the early warning procedure should work.
"If an alert had been released five minutes before the tsunami hit land," Ni said, "a huge number of people would have been saved."
The December 26 tsunami, resulting from an earthquake off the coast of Indonesia, claimed more than 200,000 lives and left another 1.5 million homeless.
Ni, professor at the Earth and Space Sciences School of the Hefei-based University of Science and Technology of China, said he, Hiroo Kanamori and Don Helmberger, both from the California Institute of Technology, found a way to spot the precise location and time span of big tremors by analyzing high-frequency signals of primary waves.
The new findings were published in the latest issue of Nature magazine.
"Most tsunamis are caused by undersea earthquakes which generate primary and secondary waves," Ni said, adding that the most powerful quakes can vibrate the earth like a bell.
Primary waves are important for quake analyses. Traditional monitoring of earthquakes focuses on collecting signals of low-frequency primary waves. But in big quakes, low-frequency signals might be overlaid by signals with higher frequencies, making research more difficult.
The 35-year-old Ni and his partners blazed a new trail in analyzing high-frequency primary waves and precisely identified the epicenter of the Indian Ocean earthquake and calculated its scale.
With data transmitted from the US Incorporated Research Institute for Seismology and the aid of two personal computers, Ni and his team assumed that the impact zone might be as long as 1,200 kilometers, even greater than the most powerful quake in human record, which occurred in 1960 off the coast of Chile.
Ni's description of the tremor was supported by Seth Stein and Emile Okal, both from Northwest University, in another research paper published in the same issue of Nature.
Ni said he hopes to further cooperate with the United States Geological Survey in data sharing and methodology discussion.
"If global cooperation runs smoothly," Ni said, "we could realize effective early warning for big tsunamis in two years, with 90 percent accuracy."
(Xinhua News Agency April 7, 2005)
