Sample Paper on Tsunami and Earthquake of Japan in 2011

Tsunami and Earthquake of Japan in 2011

A tsunami is a cycle of huge waves resulting from underwater disturbance in a large water body. It can be triggered by geological processes such as earthquakes, volcanic explosions, meteoric or cosmic forces. On 11th March, 2011 a huge 9.0 magnitude earthquake hit Pacific Ocean, about 129 kilometers east of Sendai Japan, 2 kilometers below sea level triggering a giant 30 feet tsunami (Malamud, 2011). The tsunami caused huge devastation of buildings and two nuclear power plants. The number of casualties as at February, 2014 was close to 16000, and damages are estimated at about $300 billion (, 2014). Earthquakes are the major causes of tsunamis and are vibrations on the earth’s surface caused by energy released when there are dislocations on the earth’s crust.

According to plate tectonics theory, the earth’s crust constitutes of eighteen plates that float on the surface on hot molten rock called mantle; as the plates drift apart, they collide with each other and pressure increases along the fault lines. The pressure can cause the plates to bend and break depending on the collision energy.  The energy released is massive causing vibrations called seismic waves that reach the earth’s surface as earthquake (Reinburg et al., 2007). In Japan, for example, the tectonic movement occurs along the Pacific plate causing it to slide under the mantle (Rhea et al., 2010). A normal fault can occur due to tension where an overlying block sinks usually in spreading zones. When two plates compress, more often than not in subduction zones, the top block can bend upwards resulting to a thrust fault. Thirdly, in transform zone, plates can slide past one another and such horizontal movement is referred to as lateral faulting (USGS, 2013).

The inner mantle is always in motion causing underground disturbances that cause shockwaves, and disruptions of the earth’s crust (The Physics of Tsunamis, n. d). Not all shockwaves are experienced on the earth’s surface; thousands of low magnitude earthquakes occur without causing devastation. A seismograph with a Richter scale measures the magnitude of earthquakes as a logarithm of the wave’s amplitude. Earthquakes of magnitude 1.0 to 2.0 on Richter scale are not felt on the surface, while earthquakes of 6.0 and above are rare and destructive when they occur (Allen, 2011).

It has been discovered that majority of earthquakes occur along fault lines zones. Japan is prone to earthquakes because it is located close to a subduction zone. There are plates at the zone that slip past one another along the fault lines, with one plate being forced under another. The movement of the thick crusts annually can be small but due to their size they collide with a lot of energy being dissipated. Immense vibrations are produced due to friction as plates glide past one another (Malamud, 2011).

Tsunamis have occurred when the origin of the earthquake referred to as the epicenter is beneath the floor of the ocean or sea. Pacific Ocean has been a source of most of the tsunamis that have been experienced in the world. Changes in the water levels are caused by the instability of the ocean floor. The earthquake in Japan’s catastrophe was caused an earthquake that was caused by slippage of one plate under the other causing a rise in sea level. Subsequently, there is turbulence of the water due to gravitational force as it regains balance (The Physics of Tsunamis, n. d).

Due to the large volume of water in involved, tsunamis produce high energy waves with high velocities of up to 600 miles per hour (National Geographic, 2011). The waves generated have long wavelengths, therefore, lose energy slowly and are able to travel many kilometers at high speed. The velocity of the tsunami decreases as depth decreases towards the coastline. However, the energy change is minimal but the waves grow in height forming tides, characterized by sudden surge of water vertically up to 30 meters (The Physics of Tsunamis, n. d; Hays, 2013). The energetic water causes floods on the land near the ocean, and the water hits objects, destroying houses and other erected structures. Tsunami water retreats to the ocean with the debris (National Geographic, 2011). The Japanese tsunami of 2011 receded with millions of tons of wreckage and people. Due to ripple effect of waves, tsunamis can continue for some time as energy is released causing more turbulence and generation of more waves.

Tsunamis are unpredictable, and their forecasting can only be based on the location of zones which have high likelihood of occurrence. Since the ability to determine time of occurrence and the magnitude has not been discovered, people living in hazardous regions can only take precautionary measures. Seismologists warn people after detecting seismic activity, minutes before tsunamis, in order to vacate regions close to the ocean. Regions that are susceptible to tsunamis, for example, Japan rely on warnings because the first waves are detected earlier. The country has also embarked on educating the citizens and trained them on how to take cover in the event of an earthquake. They also construct swinging buildings that are resistant to collapsing when shaken by earthquakes (Malamud, 2011).


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