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Tsunami and physics
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Tsunamis are waves, or series of waves, created by a disturbance in the ocean. Most of the time this disturbance is by an earthquake but can be from meteorites, landslides, or even explosions. They are sometimes known as tidal waves but this is a misnomer because tsunamis have nothing to do with tides. While tsunamis are feared particularly in light of the December 26th tsunami, the physics behind them is fascinating.
One the largest tsunamis in recent history was the Cascadia tsunami in 1700. This occured when two continental plates (stretching from Vancouver to California) slipped causing a 9.0 magnitude earthquake. The resulting tsunami stretched across the entire Pacific and is recorded in Japanese history. Researchers have recently found the evidence in the Washington/Oregon area of the huge tsunami there. Both Japanese and Northwest Native American cultures tell of the tsunami. Japanese historians say that the tsunami was over 5 meters tall, and Native American legends tell of landslides and entire villages disappearing in the same time period.
Most of the information about tsunamis is from the last century and specifically the last 50 years; this is because this is when we have just started to understand the physics behind them.
Most of the major tsunamis that have occured are in the Pacific because there are much more earthquakes in the Pacific "Ring of Fire". The Pacific tectonic plate is very active and causes sucduction and slipping between plates, thus causing many earthquakes.
Another large tsunami occured in 1946. This was caused by a 7.8 earthquake on the Aleutian Islands that spread to Hawaii. There was little warning in Hawaii and a large death toll followed. The result of the tsunami was 165 deaths ...
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...56 before the advent of sonar and modern depth techniques. The scientists knew the amount of time it took for the tsunami to reach Hawaii from Alaska, and also the distance, so they thus knew the velocity. Since g is already known, they simply solved for the average ocean depth.
Another factor in the creation of tsunamis is the depth of the earthquake. If the earthquake occurs more than 100 km below the surface, a tsunami will not occur because there is not enough vertical displacement of the water.
Bibliography
"Physics for Scientists and Engineers", (2004), Serway and Jewett, Brooks/Cole Thomson Learning
"Furious Earth - The Science and Nature of Earthquakes, Volcanoes, and Tsunamis", (2000), Ellen Prager, McGraw-Hill Publishing
"The Official Tommy Tsunami and Ernie Earthquake Coloring Book", (1980), Jewell Hermon, Alaska Emergency Services
The scenario mentioned above was based on the rupture located along the Cascadia fault line. This fault system runs from Northern California to Vancouver Island about 700 miles off the shore (FOX5). Scientists use to believe that the San Andreas Fault was where a large earthquake tsunami would originate, but recently their attention has shifted to the Cascadia subduction zone which is now said to be much more dangerous than previously thought (FOX5). Recent earthquake events have added even more tension and possibility for a large-scale tsunami. On March 10, 2014, a 6.8 magnitude earthquake struck off the coast of Northern California, which put a lot of stress on the Mendocino Triple Junction (Davidson). The Mendocino Triple Junction is where three tectonic plates collide, and is very unstable (Davidson). This junction has all this built up pressure and is about ready to explode. Scientists believe that this junction will be the origin of a tear along the 680-mile long Cascadia Subduction Zone. (Davidson). The disaster that follows will be considered the United State’s largest modern-day earthquake.
Tsunamis can go the same speed as a jetliner and that massive wave can out run the fastest runner. When there is a lot of waves at once, or the water goes back that is a sign that a tsunami is coming. If that tsunami is far then people need to get to the tallest and strongest building there is in the city that way they are safe and helicopter can pick them up. Tsunamis can wipe out an entire city or 1/4 of the country. Tsunamis can last up to an hour, or more.
Gordon, Mary, and Cameron King jr. "Earthquake and Fire in San Francisco." University of California Press. 48.1 (1985): 69-79. Web. 5 Mar. 2014. .
The 2004 Indian Ocean earthquake and tsunami took place on December 26th, 2004 and had a magnitude of 9.15. The cause of the Sumatra Tsunami was due to the sliding of two tectonic plates. Sumatra, an island in Indonesia, is situated on the boundary of the two plates; part of Sumatra is situated on the India/Australian plate and the other part is on the Eurasian plate. The Indian/Australian plate and Eurasian plate connect on the ocean floor at the boundary, a little over 100 miles off the short of Sumatra. Sumatra was one among the many countries that was impacted by these natural disasters. To fully understand the Sumatra Tsunami one must examine the events that led up to it, what a tsunami is, and the damage caused.
study of the San Andreas fault system." (USGS) When the 1906 earthquake struck scientist set
The Great Kanto Earthquake also known as the Tokyo-Yokohama Earthquake of 1923 hit the metropolitan area of Kanto on September 1st, 1923 around 11:58 pm. It was a 7.9 on the Richter magnitude scale, killing over one-hundred and forty thousand people due to its high magnitude and the time it happened. The earthquake struck around lunch time, when many Japanese people were at home cooking at their charcoal or gas fueled stoves. At the moment the earthquake hit, it knocked down buildings that caught flames from the stoves that fell over, enflaming the city. The fire was swept up and able to spread due to the gusts of wind that occurred for two days afterwards, resulting in firestorms. Charles Blauvelt experienced the ordeal of the fire describing the flames as “[covering] the whole city [as they] burned all day and night.” In addition to the firestorms and the earthquake itself, there was a shock because of all the fallen debris which triggered tsunamis to fill and flood Japanese cities. These tsunamis, that were about thirty feet tall, destroyed central Tokyo and immensely added to the death toll.
“United States. National Park Service. "1906 Earthquake: Law Enforcement."National Parks Service. U.S. Department of the Interior, 27 Apr. 2014. Web. 10 May 2014.
Additionally, this earthquake occurred on a thrust fault. This fault was a subduction zone slip which occurred primarily beneath the ocean were the Pacific plate plunges underneath the North American plate. This sudden upward movement of the sea floor along the rupturing fault generated a massive tsunami. This vertical deformation
Gammon, Crystal. "Massive Sea-floor Shove Triggered Japan's Tsunami." LiveScience. TechMedia Network, 02 Dec. 2011. Web. 16 Mar. 2014.
In March of 2011, Japan suffered one of the largest most powerful earthquakes to hit Honshu, Japan. (“Facts about Japan”) The earthquake registered 8.9 and was the fifth largest most powerful earthquake in the world.... ... middle of paper ... ...
An earthquake occurs abruptly and causes severs damage to people, property, landscape and more. A great mega-thrust earthquake, known as the Great Tohoku Earthquake has shaken Japan at 5:46:24 UTC on March 11, 2011. It caused a severe disaster, including tsunami and nuclear radiation exposure.. This mega-quake located at the latitude 38.297 degree North and longitude of 142.372 degree East, near the east coast of Honshu, Japan (USGS, 2013). An earthquake and tsunami waves caused widespread damage to many areas of Japan. People in Japan are still recovering from the damages.
Tsunamis are barely noticeable in deep ocean water; however when it starts approaching the land and shallow water the waves start to slow down and the height starts increase sometimes reaching heights of over 100 feet (30.5 meters).
"Earth Island Journal." A Rising Ride Sinks All Islands Vol. 11. Fall 1999. 15 Jan 2005 .
The death toll climbs to over 10,000 and is still rising (Branigan 2). The disaster in Japan began without warning on Friday March 11, 2011 at 2:46pm with a 9.0 magnitude earthquake, the strongest ever recorded in the country (Fackler 3). A massive thirty-three foot high tsunami, generated by the earthquake, swept over lands in northern Japan, taking objects and debris with it. To make matters worse, the tsunami caused the cooling systems at several nuclear power plants to fail. The disaster in Japan was a tragic event, and it had a plethora of causes and effects.
Earthquakes belong to the class of most disastrous natural hazards. They result in unexpected and tremendous earth movements. These movements results from dissemination of an enormous amount of intense energy in form of seismic waves which are detected by use of seismograms. The impact of earthquakes leaves behind several landmarks including: destruction of property, extensive disruption of services like sewer and water lines, loss of life, and causes instability in both economic and social components of the affected nation (Webcache 2).