The Frequency and Effects of Earthquakes around the World

By Nicky Lee

Introduction

Recently, one big shock damaged Haiti. It caused numerous effects to wound many people and damage many buildings. Earthquakes are one of many catastrophes. Sometimes an earthquake is related to a Tsunami which is a hazardous natural disaster from the deep sea or ocean. According to the experts, “Tectonic earthquakes will occur anywhere within the earth where there is sufficient stored elastic strain energy to drive fracture propagation along a fault plane. In the case of transform or convergent type plate boundaries, which form the largest fault surfaces on earth, they will move past each other smoothly and seismically only if there are no irregularities or asperities along the boundary that increase the frictional resistance” (“Earthquakes”). As you read, the natural disasters such as earthquakes, tsunamis or avalanches damaged nature and people who are especially poor and completely destitute. Of course, some of the geologists who are specialists of plate tectonics are still studying up on earthquakes and researching the makeup of the soil. A great amount of pressure will occur underneath the mantle of the Earth while the Earth’s plates are moving in the opposite direction of each other. The lithosphere, which is the rigid outer layer of earth, would break when the pressures from the Earth break out. For instance, think about a little stick. When you give a force to each side of a stick, it is easier to break than when you just set it in a normal position. Actually, this is similar to earthquakes. It means that two forces between different sides of the lithosphere are powered to each side. When these pressures and stresses are great enough, the crust will break. After the crust breaks, the pressure will decrease as energy is moving among the Earth's layers in form of waves, and earthquakes happen. People need to recognize some information about earthquakes, especially, the size and frequency of occurrence, records of earthquakes’ effects, and how to measure the earthquakes’ degrees.

Size and Frequency of Occurrence

Usually minor earthquakes are taking place nearly constantly around the world like in Alaska or Oklahoma in the U.S. as well as on the Asian continent. Also, these usually occur in Chile, Peru, Indonesia, Iran, Pakistan, the Azores in Portugal, Turkey, New Zealand, Greece, Italy, and Japan, but earthquakes can occur almost anywhere, including New York City, London, and Australia. Larger earthquakes, however, come about less frequently. Therefore a few countries or cities are damaged badly seismically by magnitudes 4~6 in a particular time period.

Most of the world's earthquakes (90%, and 81% of the largest) take place in the 40,000-km-long, horseshoe-shaped zone called the circum-Pacific seismic belt, also known as the Pacific Ring of Fire, which for the most part bounds the Pacific Plate. Massive earthquakes tend to occur along other plate boundaries, too, such as along the Himalayan Mountains. With the rapid growth of mega-cities such as Mexico City, Tokyo and Tehran, in areas of high seismic risk, some seismologists are warning that a single quake may claim the lives of up to 3 million people(“Earthquake”).

Measuring the Size of An Earthquake

Magnitude (“Earthquakes and Volcanoes”)

Modern seismographic systems precisely amplify and record ground motion (typically at periods of between 0.1 and 100 seconds) as a function of time. This amplification and recording as a function of time is the source of instrumental amplitude and arrival-time data on near and distant earthquakes. Although similar seismographs have existed since the 1890's, it was only in the 1930's that Charles F. Richter, a California seismologist, introduced the concept of earthquake magnitude. His original definition held only for California earthquakes occurring within 600 km of a particular type of seismograph. His basic idea was quite simple: by knowing the distance from a seismograph to an earthquake and observing the maximum signal amplitude recorded on the seismograph, an empirical quantitative ranking of the earthquake's inherent size or strength could be made. Most California earthquakes occur within the top 16 km of the crust; to a first approximation, corrections for variations in earthquake focal depth were, therefore, unnecessary.

Largest and Deadliest Earthquakes by Year (1990 – recent)

The largest earthquakes since 1990 occurred off the West Coast of Northern Sumatra in Southeast Asia. Many people who enjoyed the leisure on the beach were killed or wounded by the biggest earthquake. Actually it was the Tsunami made by earthquakes. It was initially reported as moment magnitude 9.0 (“2009 Sumatra Earthquakes”). The hypocenters of main earthquakes were approximately 160 kilometers (100 miles). According to the U.S. Geological Survey, a total of 227,898 died and this is one of the ten worst earthquakes on record (“2009 Sumatra Earthquakes.”).

The deadliest earthquake occurred in Haiti in January 2010. Until now, it is impossible to count and estimate how many people have died because there has been a lot of destitution and rescue and search team have had problems.

Conclusion (Prevention)

As you know, earthquakes, which are kinds of natural disasters in the world, are shaking of ground caused by movement of the earth’s crust. Although the Earth’s plates are moving in the opposite directions of each other, they make great impacts on the lithosphere. When the plates move, they stress on each other and themselves. When these pressures and stresses are great enough, the crust breaks. After the crust breaks, the pressure will decrease as energy moves among the Earth's layers in the form of waves, and earthquakes happen. Many scientists are continuously thinking of ways to try and reduce earthquake power. Some are trying to lessen the friction between colliding plates. According to the special instruments that are now in existence to give warnings in California, Japan, and New Zealand, little vibrations show if land has begun to shift dangerously on a certain side of a fault. Other instruments are used to detect certain gases collecting in groundwater.

Architects are also designing earthquake-proof buildings, constructing on rock instead of gravel, or on soft sand or clay. Large structures are made with strong frameworks of steel or reinforced concrete, so that the frame stands firm even if the ground is shaking. The pyramid-shaped Transamerica building in San Francisco was designed in this fashion. Researchers are always trying to reduce the impact of earthquakes. They continue to study and experiment with ways to tame the Earth. However, we all still have much more to learn before we can control the power of one of nature’s most amazing phenomena.

Works Cited

“2009 Sumatra Earthquakes.” http://en.wikipedia.org/wiki/2009_Sumatra_earthquakes
Archer, Jules. Earthquake! New York: Crestwood House, 1991. 10 Feb 2010.

“Earthquakes.” Wikipedia. Web. 28 Jan. 2010.

“Earthquakes.” http://mediatheek.thinkquest.nl/~ll125/en/earthqke.htm

Lampton, Christopher. Earthquake. Brookfield, Connecticut: The Millbrook Press, 1990. 10 Feb 2010.

Spence, William, and Stuart A. Sipkin, and George L. Choy. Earthquakes and Volcanoes. Volume 21(1). Web.1989. 4 Feb 2010.

Van Rose, Susanna. Eyewitness Books: Volcano & Earthquake. New York: Alfred A. Knopf, 1992. 10 Feb 2010.