Physics of Tsunamis

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Physics of Tsunamis

This paper will discuss the physics and warning systems of tsunamis, a destructive wave force that researchers have been studying for many years. Tsunamis are different than tides or surface waves because undersea earthquakes, instead of winds or the gravitational pull of the moon or sun, generate them. They can reach speeds of up to 700 kilometers per hour but can be undetected until they reach shallow water, then unexpectedly arise as deadly waves.

Tsunamis evolve from three physical processes, which are generation, propagation, and inundation of dry land. The propagation phase is the most understood, whereas generation and inundation are more difficult to model with computer simulations. Researchers apply a linear wave theory to the propagation phase, which assumes that the small height of the wave compared with the wavelength does not affect the wave’s behavior. Their theory predicts that the deeper the water and longer the wave, the faster the tsunami. Upon inundation, the wave height is so high that the linear wave theory fails to describe the interaction between the water and shoreline.

Emergency planners have struggled with getting reliable confirmation of the existence of tsunamis. This has snowballed into a seventy-five percent false alarm rate since the 1950’s. There are plans being put into place to upgrade the warning systems, but the success of improved safety will also depend on the people’s response. The education of coastal communities on evacuation routes and procedures is crucial to improvement of the current tsunami emergency evacuation plans.

Physics of Tsunamis

To fully understand tsunamis, it will be helpful to first distinguish them from wind generated waves or tides. Ocean breezes can crinkle the surface into relatively short waves that create currents that are restricted to a shallow layer. Strong winds are able to whip up waves that are 30 meters or higher but even these do not move deep water as the tsunamis do. Tides, which sweep around the globe twice a day, also do not produce currents that reach the ocean bottom. Unlike true tidal waves, however, tsunamis are not generated by the gravitational pull of the moon or sun. A tsunami is produced by an undersea earthquake, or much less frequently, volcanic eruptions, meteorite impacts, or underwater landslides. Even though tsunamis can reach speed...

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... better evacuation routes. With the combination of technology and community awareness, coastal residents will have a much better chance at avoiding the destructive forces of these killer waves.


Tsunamis have been a major threat to coastal areas for many years. The challenge in the past has been early detection; due to the way they speed towards the coastline hidden in deep waters, only to surface close to the shore as a powerful, destructive wave. However, with recent advances in technology and a better understanding of nature’s ways, we may be able to protect property and people by educating them on these powerful waves.

People in the tsunami’s path must use the current warning system improvements in conjunction with a timely response to avoid future catastrophes. Community education programs would seem to be a good starting point. If researchers, emergency planners, and community leaders will work together in a team effort, I believe the death toll and property damage will be kept to minimal figures.


Gonzales, Frank. “Tsunami” Scientific American 280, no. 5 (May 1999): 56-65. Describes the physics of tsunamis and early warning systems.

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