Earthquakes the Major Earthquake That Struck Offshore Essay

  • Length: 5 pages
  • Sources: 5
  • Subject: Geography
  • Type: Essay
  • Paper: #21848046

Excerpt from Essay :


The major earthquake that struck offshore from Japan in March, 2011, was one of the largest earthquakes experienced in that region of the world in many years. It caused massive damage and it spawned a powerful tsunami that literally wiped many Japanese towns off the map. The causes of earthquakes are known to scientists, although science has not yet become sophisticated enough to predict when and where an earthquake will occur. This paper reviews the many aspects of earthquakes and the ramifications of those disruptions of the earth's crust.

Causes of earthquakes: The United States Geological Survey (USGS) explains that an earthquake happens "when two blocks of the earth suddenly slip past one another." The surface of the ground where the slippage took place is called the "fault" or the "fault plane." The earth actually has "four major layers, the inner core, outer core, mantle and crust," the USGS explains. The "skin" of the planet is the "mantle" and it is made up not of one solid piece, but of a number of pieces joined together in jagged edges "like a puzzle covering the surface of the earth"; what's more, these jagged pieces keep moving, they slide past one another, they crash into each other, and they are actually called "tectonic plates" (USGS).

The great majority of earthquakes result from these tectonic plates interacting with one another. The edges are jagged, as noted previously, and they are very rough, so they lock together over many years. But when the pressure has built up sufficiently they become un-stuck, and that break causes an earthquake.

How are earthquakes measured? The USGS explains that the intensity of the earthquake depends on the "amount of slip on the fault," and it is measured with seismogram recordings on the surface of the earth. The seismograph records the intensity of the earth's movement at the fault line. The slippage at the fault line causes the seismograph to create wiggly lines on the seismograph; short lines that "don't wiggle very much" means a small earthquake has taken place, but a long wiggly line that "wiggles a lot" means it was a large earthquake; the "length of the wiggle depends on the size of the fault, and the size of the wiggle" reflects the amount of slip on the tectonic plates (USGS).

How do earthquakes cause damage? According to the College of Charleston the damage from an earthquake is caused according to the way energy moves through the earth matched with how the geology of that area allows the energy to flow through. For example, a very hard rock like limestone or granite, might "vibrate very quickly with short movements" but it won't likely break apart. But when the earthquake happens in wet sand, or silt, the shaking will likely be more intense; in this case the soil may respond like a liquid, hence the word "liquefaction" comes into play. When an earthquake happens in a sandy area, and liquefaction takes place, great damage can occur and buildings, roads and other items on the earth will tend to sink with liquefaction. However, a wooden building tends to bend in an earthquake while masonry "tends to shatter"; that means that building made of reinforced steel will stand a violent shaking more than buildings that are not supported with steel (South Carolina Earthquake Education & Preparedness Program -- College of Charleston).

The Limitations of Earthquake Prediction: The USGS admits that they cannot predict earthquakes; no scientists from USGS or from Caltech "…nor any other scientists have ever predicted a major earthquake." That having been said, it is true that "probabilities can be calculated for potential future earthquakes," the USGS explains. The USGS gives an example in that scientists have estimated that within the next "30 years" there is a probability that a major earthquake will occur in the San Francisco Bay area; there is a 67% chance that a huge earthquake will happen in San Francisco, the USGS asserts, and there is a 60% chance of a major earthquake in southern California. Since they can't be certain as to when a big one will happen, what needs to be focused on, the USGS continues, is to help improve "the safety of structures" rather than trying to accomplish any prediction as to exactly when one will happen.

Geological change from earthquakes: The massive 9.0 magnitude quake that caused enormous damage in Japan caused changes to the geology of that area of the world. According to, the USGS reported some "startling information" regarding the geological changes following the Japanese quake. For example, Earth's axis apparently shifted "10 inches" resulting from the earthquake. Japan's coastline shifted by 2.4 meters and it was a "permanent" shift. There were a reported 100+ aftershocks that measured 5.0 or more after the main major quake, the site explains. Moreover, the quake was 900 times as strong as the huge earthquake that rocked San Francisco in 1906 and media outlets in St. Louis, Missouri that the city "moved an inch as a result of the [Japanese] quake" (p. 2).

Major Earthquake area: It is often the case that people east of the Mississippi believe the majority of earthquakes happen in California. Actually, according to the USGS, most earthquakes -- about 90% of them -- happen on what is called the "Ring of Fire," also known as the Circum-Pacific belt. It is a zone of very active earthquake faults that surround the Pacific Ocean. The ring of fire extends up the western coast of South America, continuing up Central American and North America, and continuing through the Aleutian Islands and into Asia and down all the way on the eastern coasts of China and Southeastern Asia down to Australia and New Zealand. The next most seismic region is called the Alpide belt, which extends from the Mediterranean region, east into Turkey and northern India. The USGS explains that about 5 to 6% of the earthquakes occur in this region.

Effected Human and Environment by Earthquake: The massive earthquake that hit Japan in March, 2011, did a great deal of damage to cities, humans, and to the environment. The powerful tsunami that was generated by the earthquake did serious damage to the Fukushima Daiichi nuclear power plant. For days the Japanese nuclear workers tried to cool down the plant, which was overheating because the tsunami had "knocked out crucial diesel back-up generators that were designed to cool the reactors in an emergency" (Brumfiel, 2011). The earthquake's powerful undersea thrusting -- two huge blocks tectonic plates suddenly slipped past one another and caused massive release of energy -- created the tsunami that actually crashed into the nuclear plant with enormous force.

In a few days, the three nuclear reactors that were operating at the time of the accident "overheated and released hydrogen gas, leading to massive explosions" How much radiation was released by this accident? The Japanese government released figures that the editors of Scientific American assert were incorrect. The Japanese did not report accurately, Brumfiel writes, because the newest information on how much dangerous, cancer-causing radiation was actually released shows far more than the Japanese government reported.

Journalist Beth Thomas writes in Bloomberg that the Fukushima nuclear plant was responsible for "…the biggest discharge of radioactive material into the ocean in history"; it was "20 times the amount estimated by its owner, Tokyo Electric Power Company (Thomas, 2011, p. 1). The study that Thomas references in her article was conducted by the Institute for Radiological Protection and Nuclear Safety, and that research indicated that an estimated "27,000 terabecquerels of radioactive cesium 137" leaked into the Pacific Ocean, and "35,800 terabecquerels of cesium 137 were released into the atmosphere" (Thomas, p. 1). Cesium can damage human cells, and cause cancer.

Earthquakes that caused enormous death and damage: The powerful earthquake that occurred in the Indian Ocean on December 26, 2004, created a tsunami that was as powerful as "23,000 Hiroshima-type atomic bombs" (National Geographic News, 2005) (NGN). An estimated 150,000 people were dead or missing in 11 different countries due to the sudden tsunami. The earthquake happened because the India tectonic plate slid under the Burma tectonic plate, and the violent shift of earth's crust in those two places -- the rupture was "more than 600 miles long" -- caused the seafloor to be displaced "horizontally" by ten yards (NGN).

In 1906, the San Francisco earthquake (estimated at 8.0 on the Richter scale) caused massive damage and took an estimated 700 lives. The tectonic plates that broke lose along the San Andreas fault for 296 miles (USGS). Much of the city burned to the ground from fires started by the quake.

Can people predict when earthquakes will occur? The answer is no.

Evacuation after an earthquake: The 5.9 earthquake that occurred in Virginia in August, 2011, was felt on the East Coast and caused "light damage" but people were ordered to evacuate the Pentagon (for safety reasons), and many buildings in New York City, Washington D.C., and elsewhere,…

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