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Monday, December 24, 2007

The GITEWS -- German-Indonesia Tsunami Early Warning System

Everyone knows by now that tsunami is generated by earth's quick. Whenever there is an earth quick, there will be potential tsunami somewhere. Presently many of the fancy numerical models don't seem to go too much beyond this simple common sense understanding. Even with the addition of buoys -- every time a tsunami disaster happens, you can count on the government will managed to add more buoys, that doesn't seem to help very much either. That's pretty much the case that led to the disaster of Indonesia tsunami three years ago.

Well, at long last, there will be changes for the better in the air! I find myself impressed by what I have just read in AFP about the GITEWS - German-Indonesia Tsunami Early Warning System. Here's the basic concept behind it:
. . . based on different kinds of sensor systems. In ca. 90 % a tsunami is generated by an earthquake but also volcanic eruptions and landslides may be the triggering events. The conception aims at achieving indicators of a tsunami and its dimension by the analysis of different measurements at a very early stage. While a tsunami wave in the wideness of the sea spreads out with a speed up to 700 km/h, in the treated region a period of about 20 minutes elapses between the wave's generation and the first contact with the Indonesian mainland. In this timeframe the sensors, which will be installed at different locations inside the considered propagation areas, are able to rapidly detect deviations from normality (anomalies).
As the figure shows, the sensors for this system, as for the general tsunamis, comprise seismometers, GPS instruments, tide gauges, and buoys, as well as ocean bottom pressure sensors.

According to the AFP article, these sensors carry out measurements every 15 seconds and relay the information to a buoy which sends the information to Indonesia via satellite,
If a quake is detected and at the same time the seabed monitors measure abnormal water pressure, another complex part of the warning system kicks in, as the German National Research Centre for Geoscience (GFZ)'s technology seeks to predict where and when the tsunami will strike the coast.

"These calculations unfortunately take a long time because, since the seabed is not even, the range of variables to be taken into account is vast. We have therefore developed models of potential trajectories to save our computers time," Joern Lauterjung of GFZ said.

The system had what his team described as a "baptism of fire" in September when an 8.4-magnitude earthquake struck off the west coast of Indonesia's Sumatra island. It measured the size and location of the seism within a record five minutes.

This enabled the GFZ scientists to raise the alert to Indonesian authorities more than 10 minutes earlier than the Pacific Tsunami Warning Centre in Hawaii.

I am not certain, but I suspect this is the first time some one recognizes and accomplishes that in order to get tangible results, it has to have detailed comprehensive measurement. It is the case for tsunami, it will be the case for freaque waves and general ocean waves also!

It took the death of some 220,000 people after the December 26, 2004 tsunami to lead to the now GITEWS. Do we really need a major disaster to do something real meaningful. Why can't we do it before the disaster happens?

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