Could Animals Detect an Approaching Tsunami?

Tsunamis are waves generated by underwater earthquakes or landslides that displace large amounts of water. These waves propagate toward land at great speeds and inundate the coast. While losses to Human life and property were great in the recent Asian-Tsunami disaster, independent reports from across affected nations indicate that animals, especially elephants, escaped the disaster. 

Our research focuses on the various ways in which the animals could have detected the tsunami-generated signals and examines the possibility of early detection of tsunamis using these mechanisms. 

A tsunami generates acoustic waves in air, due to undulations on the sea surface, akin to that of a drum-membrane vibration. Whilst tsunamis in deep water travel at speeds close to the sound speed in air (330 m/s), they slow down as they approach shallower water (to about 10 m/s). As a result, the sound waves generated in air due to the tsunami travel much faster than the tsunami itself and so, could serve as a potential early warning signal to warn the animals. 

Besides the Acoustic waves in air, the pressure variations on the sea bottom due to the tsunami wave motion also generate seismic waves in the sea-bottom, which propagate toward land at speeds much higher than the tsunami wave. A particular wave, called a Rayleigh wave, constitutes a major proportion of the ground displacement. These typically travel at about 1800 m/s, suffering cylindrical spreading loss as they propagate toward shore. 

Both these signals have the potential to serve as early warning signals for elephants, which are known to pick up infrasound (i.e. low frequency sound) signals. Our research focuses on developing models for both mechanisms and answering interesting questions of remote sensing abilities in animals.