Tsunami: How They Work and How We Cope With Them

Scott Hughes
Idaho State University
Department of Geosciences

Tsunami, also known as “great waves,” occur when the ocean becomes disrupted by violent forces of nature.  Tsunami are caused by earthquakes, volcanic explosions, landslides, and even meteorite impacts.  Most are caused by earthquakes, which will be discussed in this lecture along with the reason a large tsunami occurred in the Indian Ocean on December 26, 2004.

Compared to regular wind-caused waves, tsunami have very long wavelengths, up to many km, and travel across the surface of the ocean at speeds similar to that of a commercial jet.  Compared to fluctuations of the sea surface due to tidal forces, tsunami cause rapid changes in local sea level with high and low levels extending much farther inland and seaward, respectively.  These distances are directly related to the land elevation.  Hence many flat coastal areas are inundated several km, so areas like Banda Aceh and Meulaboh, Indonesia, and Phuket, Thailand, are severely damaged and experience significant loss of life and property.

Our understanding of tsunami are helping to predicting, and even forecast such devastating events.  We will finalize our discussion with an explanation of the tsunami warning system that covers most of the Pacific Ocean, and how the Deep-ocean Assessment and Reporting of Tsunamis (DART) is being implemented.

Scott Hughes
Idaho State University
Department of Geosciences