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Can HF Radar detect Tsunamis ?

The 11th March 2011 Sendai Tsunami could be observed at the coast of Cile close to Conception 22 hours after generation. First results have been presented on the ROS 2011 workshop.

After the tsunami disaster at 26th December 2004 causing more than 260,000 lifes lost, the possibilities of HF radar to detect tsunami waves have been investigated. In contrast to wind-driven ocean surface waves, a tsunami's energy is distributed all along the water column from the surface to the bottom of the ocean. In wave theory, tsunamis have to be considered as shallow water waves, thus the tsunami's speed can be calculated by v = sqrt(g h)
tsunami speed vs. depth tsunami speed vs. depth
In the deep ocean, where the speed of a tsunami is in the order of 700 km/h at a waveheight of less than one meter, there is most probably no signature connected to the tsunami which can be seen by HF radar. However, when the tsunami travels into shallow water, e.g. at the shelf edge, the tsunami slows down in speed and gets transformed to a shorter wavelength. This process is connected to a strong ocean current signature along the tsunami front. As the bottom topography along the path of the tsunami plays a significant role if one wants to describe the tsunami's waheheight and the connected current pattern as a function of time, a numerical model simulation has been performed for the area of

using the initial conditions given by the strength and location of the earthquake of 26 December 2004.

The model results presented above show current fields with speeds up to 2 m/s which provide some evidence that such features can be most probably be detected and tracked by HF-radar, presumed that the radar technology allows for sufficient short integration times (roughly 4-5 minutes), as the tsunami 'signature' is very quickly passing through the radar ranges. This should be possible with WERA. Further investigations will be conducted in the near future.

The model has been set-up and run by Alexei Androssov in cooperation with Angelo Rubino.
They have provided a description of the model.


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