How to forecast a tsunami?

Mathematicians from Novosibirsk and Krasnoyarsk, working on a joint project with American colleagues (sponsored by the CRDF and the Federal Agency for Science and Innovations (Rosnauka)) have improved the tsunami forecasting system. To this end, they applied the method of the so-called circulation of tsunami data obtained in a real-time mode. This newest method is based on the latest results achieved by researchers in the theory and numerical algorithms of inverse problem solution.

A tsunami, which means “a wave in a harbor” in Japanese, is a grandiose sight with disastrous effects. It can be caused by the underwater earthquake and a volcano’s work, or even by falling of a large landslip or a huge piece of ice. The majority of tsunamis originate from the Pacific Ocean. This ocean is not “pacific” at all, as more than three fourths of all active volcanoes of the Earth are hidden on its bottom. Unfortunately, tsunami forecasting remains a complicated task, waters continue to take away hundreds of thousands of lives. Firstly, not every earthquake results in a tsunami, secondly, dangerous waves are not seen from ships or satellites in the majority of cases. Sometimes, the waves running at an aircraft’s speed are small at the depth but they turn into billows near the coast.

Researchers are trying to determine how and where the tsunami will spread and how dangerous it can be to coastal zone inhabitants. To this end, firstly, tsunami recorders and tsunamometers should be installed in the ocean. By the way, such devices have been installed by the US environment protection laboratory – P?EL NOAA – in seven points of the Pacific Ocean. They allow to transmit up to 98 percent of data and to measure tsunamis with the amplitude of less than one centimeter. Once the first tsunami data becomes available, it should be processed quickly and accurately with the help of mathematical models, the forecast should be made and people should be warned about possible danger.

A group of Siberian researchers (the Sobolev Institute of Mathematics, Siberian Branch of Russian Academy of Sciences, Novosibirsk State University, Krasnoyarsk, etc.) has developed such software module. Special algorithm determines the tsunami source by processing records from deep-water oceanic receivers. The researchers built the software into the tsunami forecast system and tested it – the method worked perfectly well. The first calculations are performed right after the first wave reaches the closest tsunami analysis station. This provides the first order forecast. When the wave reaches the next station, the computations are repeated for both stations thus obtaining the second order forecast and so on.

However, the researchers say that the preliminary calculation system still needs significant improvement. They developed three new independent circulation methods for tsunami forecasting. “The methods applied to tsunami data circulation can also be used for investigation of the problem of optimal recording station placement in the ocean. Additional stations should be installed in locations that provide the most effective forecast”, says Mikhail Lavrenev, Russian project manager.

To raise the tsunami forecasting quality, the researchers suggest that the models should include special algorithm for determining initial shift in tsunami source based on two-dimensional inverse problem solution. This algorithm allows to restore the tsunami source by records of its waves at recently created stations. The researches claim that the development of neuronet software module will help to define more precisely the initial shift in the source.

Russian scientists’ large-scale project intended to improve the tsunami forecasting quality will also assist in finding appropriate locations for placement of new deep-water oceanic stations. The researchers are planning to test new investigations at the Pacific and Alaska tsunami notification centers.