Tsunami (source code)
= Tsunami
{wiki}
A <tsunami> is a train of long <surface gravity waves> generated by a rapid displacement of water, for example by seabed motion during an <earthquake> or by a <landslide>. Its wavelength can be much greater than the ocean depth, so the <shallow-water approximation> can apply even in a deep ocean.
In that limit the wave speed is $c=\sqrt{gH}$. The long wave can cross an ocean while its surface height remains small offshore. Entering shallower water lowers its speed and shortens its wavelength; coastal geometry, focusing and nonlinear flow then control amplification and inundation. Source displacement and <bathymetry> are therefore needed alongside an earthquake magnitude to predict local effects.<Tsunami Propagation by National Oceanic and Atmospheric Administration>[Propagation description: depth-dependent speed, long wavelength and coastal shoaling]{ref}
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