A tsunami warning system using an ionospheric technique

Earthquakes generate Rayleigh waves which travel along the surface of the earth about 20 times faster than the potentially destructive tsunami (if one is also generated) and reach distant points several hours before the tsunami. The Rayleigh wave excites an upward-propagating acoustic wave which, because of the exponential decrease in air density with height, increases to a large amplitude at ionospheric heights and produces ionization density changes in the ionosphere proportional to the amplitude and form of the wave. HF radio signals reflected from the ionosphere are Doppler-shifted by these motions and can be processed to produce a record which is a faithful reproduction of the Rayleigh wave. By analyzing the ionospheric record and tracing the Rayleigh wave back to the earthquake's epicenter, the characteristics of the earthquake can be determined. This information can then be used to deduce the probability that the earthquake generated a tsunami Instrumentation for a tsunami warning system based on this method is simple and inexpensive.