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Earthquakes and their consequences
History on earthquakes essay
Assignment about earthquake
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1: Introduction
Earthquakes are one of the most destructive natural disasters. They can cause many other natural disasters for example, tsunamis, avalanches or volcanic eruptions. Earthquakes occur when one tectonic plate collides with another.
There are 15 main different tectonic plates spread around the globe. Earthquakes can be recorded with seismometers. The magnitude of Richter is the most common scale. Earthquakes are movements of the Earth caused by the release of stress accumulated by geologic faults or by volcanic activity. In the last years, many scientists think that drilling for oil and gas (fracking) causes earthquakes too. There are three different types of earthquakes that will be defined in this discussion.
2: Discussion
Earthquakes:
The magnitude is used to quantify the
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Volcanoes:
When violent volcanic eruptions happen, impulsive disturbances are susceptible of generating an Earthquake or a Tsunami. Tsunamis generated by Volcanoes are infrequently.
Meteorite impact:
Asteroids and meteors colliding with earth are really rare but the “scientists realize that if these celestial bodies should strike the ocean, a large volume of water would undoubtedly be displaced to cause a tsunami.” Meteor impact is the less common factor that could generate a tsunami. Tsunami generated by meteoric impacts is very rare.
Landslides:
Icefalls, rock falls and underwater slumps or landslides could move water that could cause a tsunami. It is rather rare that a landslide cause a tsunami.
Earthquakes:
Tectonically movements of plates that generate tsunami can create a fault that could cause a Tsunami. Earthquakes are the most common generator of tsunamis.
The tallest tsunami ever recorded was 1,720 feet tall, which is approximately the height of one tower of the World Trade Center. This occurred in 1958 when a landslide fell into a fjord in Alaska.
Volcanic
Earthquakes are best described as a shaking or vibration of the ground caused by breaking of rock. Sometimes they are very strong and other times you would hardly notice them. This shaking occurs when stress that builds up in the crust is suddenly released as the crust breaks free and/or slides against the other pieces of crust. Earthquakes may also be thought of as the breaking of a popsicle stick by applying pressure to both ends at the same time. Should you try this experiment , you will feel the pressure build up as you apply more force until the stick snaps. When the stick snaps you will feel an instant of pain at your fingers as the stress reduces and energy waves move throughout the stick. When the earth's crust is placed under similar types of stress, binding as the stress builds, it will also snap and release the energy into the surrounding rocks, 'ooch'. Thinking about earthquakes will become more clear if you try another experiment.
Tsunamis caused by the Earthquake leads to flooding along the coastal environment. This damages any homes. Flooding caused new lakes or sag ponds on the land. Increasing groundwater flow from springs and displacing stream channel. ("Flood Consequences")
Earthquakes, by Webster’s dictionary definition, are, “a shaking or trembling of the earth that is volcanic or tectonic in origin.” World Book Encyclopedia reports scientists believe that more than 8,000 earthquakes occur each day without causing damage. A little more than 1,000 each year are strong enough to be felt. Earthquakes occur in the general sense, anywhere on land. Other earthquakes go by different names, such as volcanic eruptions and tsunamis, large tidal wave storms that occur underwater, primarily in the Pacific Ocean.
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.
A tsunami is a series of waves “created by an underwater disturbance such as an earthquake, landslide, volcanic eruption, or meteorite” (ready.gov). Tsunami waves are quite different from normal waves. Once a tsunami is set in motion there is no way to really “prevent” it fully, or to stop such an event. Precautionary steps can be taken, such as in Japan where a sea wall was built to protect people and property. However, this was a futile attempt since in 2011 a tsunami was able to surge over the wall, with the water building up and rushing over the top. The lesson learned is that one should not
TOHOKU, Japan, Friday, Mar. 11 -Yesterday, a 9.0 magnitude Earthquake struck the east of Tohoku, Japan. The epicentre of the earthquake was located approximately 72 km east of Tohoku (38.3 degrees North latitude and 142.4 degrees East longitude), or 130 km east of Sendai as shown by the X in figure 3 below. The focus of the earthquake was 24.4 km under the epicentre. The earthquake therefore caused a tsunami due to the displacing of water above the Pacific Plate. The earthquake and tsunami together have caused approximately 20,000 deaths, 6152 injuries and 2500 people missing. Approximately 90% of these deaths were by drowning. Approximately 140,000 people have been displaced and over 500,000 buildings and structures have been destroyed or damaged. The early warning system of Japan stopped many bullet trains, and many residents received texted warnings of the earthquake and tsunami on their mobile phones giving them time to evacuate. Figures 1 and 2 show exactly how destructive the tsunami caused by the Tohoku Earthquake was.
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.
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
While the early warning saved thousands of people, the Japan’s Meteorological Agency underestimated this earthquake as the subduction zone of Japan should not produce the magnitude 9.0 quake (Oskin, 2013a). The Tohoku Earthquake and its tsunami approximately killed 16 thousand people, injured 6 thousand people and around 3 thousand people were missing. Most people died from drowning. Around 300 thousand buildings, 4000 roads, 78 bridges, and many more were affected by the earthquake, tsunami, and fires from leaking oils and gas. Electricity, telecommunication, and railways were severely damaged. The debris of 25 million tons was generated and carried out to the sea by water (BBC News, 2012). The country’s authorities estimated more than 309 billion US dollars of damages. Landslides occurred in Miyagi and liquefaction in Chiba, Tokyo, Odaiba, and Urayasu (USGS, 2013). Furthermore, the tsunami destroyed protective tsunami seawalls. Approximately 217 square miles of Japan covered in water (Oskin,
Gammon, Crystal. "Massive Sea-floor Shove Triggered Japan's Tsunami." LiveScience. TechMedia Network, 02 Dec. 2011. Web. 16 Mar. 2014.
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).
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 are vibrations felt at the surface of the earth which are caused by disturbances of the energy in the earth's interior. These vibrations are known as seismic waves. (Skinner Robinson McVerry 1) There are different type sof seisimc waves such as Primary (P) waves, whcih travel the fastest, Secondary (S) waves which cause the earth to vibrate vertically, Surface (L) waves. P and S waves are "affected by changes in the density and the rigidity of the materials through which they pass." (Columbia Encyclopedia) Earthquakes vary in their intensity and duration. Often times they are strong enough to cause massive destriction. Tall buildings often suffer as a result of these natural disasters. In recent years this has become a larger and larger threat with both the number of large buildings, and their number of occupants increasing. In an effort to try to minimize the damage caused by earthquakes many some engineers focus primarily on designing and constructing earthquake resistant buildings. Earthquake engineers have gathered much of their information from analyzing past earthquakes, and learning which buildings can and can't withstand the tremors. The goals of these engineers is to design buildings that can withstand moderate earthquakes and obtain minimal damage, and that the buildings will not collapse lowering the probability of human deaths.
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).