Tsunamis - Wave of Destruction

Running Head: Tsunami: Wave of Destruction

Tsunami: Wave of Destruction

Abstract

The purpose of this paper is to discuss the article “Tsunami!” written by Frank L. Gonzalez, a leading researcher with the National Oceanic Atmospheric Administration at the Pacific Marine Environmental Laboratory in Seattle Washington. It is my intent to outline several key points the author makes about tsunamis that have occurred between 1990 and 2000. This paper will attempt to inform the reader about the forces that generate tsunamis as well as the physics involved with their wave propagation, speed at which they travel, and eventual contact with coastal areas. Additional topics will introduce the newest scientific methods of detection, early warning systems, and the preparations that are underway to prepare the public as to the dangers associated with tsunamis.

Tsunami: Wave of Destruction

Tsunamis are clearly one of the most destructive phenomenons in nature. They are capable of transfer of an inconceivable amount of energy and can strike heavily populated areas with little or no warning destroying anything they encounter. Researchers are studying the causes and attempting to developed systems which can detect and warn inhabitants of the approach of these destructive waves.

REVIEW

At exactly 6:49 p.m. an earthquake with a magnitude 7.1 in the Bismarck Sea approximately 19 miles from villages of Sissano, Arop, Warupu, and other small villages took the lives of over 2,200 people. Within minutes the 15 meter high wave struck the unsuspecting villagers, destroying everything in its path. The cause of this horrific event was the product of the highly active tectonic plates around the Pacific Rim. 86 percent of all tsunamis in this area are caused by undersea earthquakes and since 1990 ten tsunamis have claimed the lives of over 4000 people. Historically, there have been an average of 52 tsunamis a decade but from 1990 to 2000 there were over 82. North and South America have not been immune to tsunamis; Hawaii, Alaska, and Nicaragua have all experienced the devastation of these massive waves. The Aleutian Islands in Alaska have been the site of 12 tsunamis since 1895. One such earthquake in 1946 produced a wave that traveled 3700 kilometers to strike Hawaii where it killed more than 165 people. Another quake in Nicaragua happened in 1992, waves 10 meters were responsible for claiming the lives of 170 people and leaving 13,000 homeless. Close to the mainland of the contiguous United States, researchers have been studying the Cascadia subduction zone. This is an area off the Pacific Northwest coast where a crustal plate carrying part of the Pacific Ocean is diving under North America.

The physics of a tsunami are differentiate them from the forces that generate wind blown waves and ocean currents. Wind generated waves can be 30 meters high; however, they only affect the surface of the ocean. Currents and tides are caused by the gravitational forces of the sun and moon which can cause flooding in coastal areas. However, tsunamis are most often caused by earthquakes, or less frequently, by volcanic eruptions, meteorites, and underwater landslides. The processes that give birth to tsunamis all share the same distinct origins, some disturbance of the water column, propagation from deeper water near the source to shallow coastal areas, and inundation of dry land. Of these three, propagation is the most understood while generation and inundation are more difficult to comprehend. Tsunamis all begin with some seafloor disturbance which results in the generation of some wave front that extends out from the source. The wave then makes its way from the deep ocean the water column is forced to compress. The forward momentum of the wave front carries it and the force of the waves behind it pushing it farther inland. Efforts are underway to assess vulnerable coastal areas and map inundation areas to provide inhabitants with some sort of early warning. NOAA is in work developing a network of deep-ocean reporting stations that can track tsunamis and report them in real time. The system is known as Deep-Ocean Assessment and Reporting of Tsunamis (DART) and the works by placing recorders on the ocean floor that sense the increase of pressure of waves passing over them. The measurements are transmitted to a buoy on the surface and relayed to ground stations via satellite and the information is then used to warn those areas possibly affected.