Physics of Tsunamis
Wendy M. Blevins
PS102 Explorations in Physics
Embry-Riddle Aeronautical University
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...