Causes And Effects Of Earthquakes Essay Example For Students

Causes And Effects Of Earthquakes Essay I chose to research earthquakes and the prediction of earthquakes because I was curious as to how they work. In this paper, Iwill discus the history of earthquakes, the kinds and locations of earthquakes, earthquake effects, intensity scales, prediction,and my own predictions. An earthquake can be defined as vibrations produced in the earths crust. Tectonic plates have friction between them whichbuilds up as it tries to push away and suddenly ruptures and then rebounds. The vibrations can range from barely noticeable toa disastrous, and destructive act of nature. Six kinds of shock waves are generated in the process. Two are classified as bodywaves, that is, they travel through the inside of the earth and the other four are surface waves. The waves are further classifiedby the kinds of motions they incur to rock particles. Primary or compressional waves, known as P waves, send particlesmoving back and forth in the same direction as the waves are traveling, as secondary or transverse shear waves, known as Swaves, create vibrations perpendicular to their direction of travel. P waves always travel at faster speeds than S waves, sowhenever an earthquake occurs, P waves are the first to arrive and to be recorded at geophysical research stations worldwide. During ancient times very little was know about. Some of the ancient Greek philosophers connected earthquakes tounderground winds, where others blamed them on fires in the depths of the earth. Around AD 130 the Chinese scholar ChangHeng, believing that waves must ripple through the earth from the source of an earthquake, created a bronze object to recordthe directions of such waves. Eight balls were carefully balanced in the mouths of eight dragons placed around the outside ofthe object. When a passing earthquake occurred the wave would cause one or more of the balls to drop. Earthquake waves were observed in this and other ways for centuries, but more scientific theories as to the causes of quakeswere not proposed until modern times. One such concept was recreated and advanced in 1859 by an Irish engineer, RobertMallet. Perhaps recalling on his knowledge of the strength and behavior of construction materials, Robert Mallet proposed thatearthquakes occurred either by sudden flexure and constraint of the elastic materials forming a portion of the earths crust orby their giving way and becoming fractured. Later, in the 1870s, an English geologist, John Milne created a device similar toone of todays earthquake-recording device, a seismograph, which in Greek seismos means earthquake. A simple pendulumand needle suspended above a smoked-glass plate, it was the first instrument to allow visual difference of primary andsecondary earthquake waves. The modern seismograph was invented in the early 20th century by a Russian seismologist,Prince Boris Golitzyn. His device used a magnetic pendulum suspended between the poles of an electromagnet, created themodern era of earthquake research. There are three general classes of earthquakes that are now recognized: tectonic, volcanic, and artificially produced. Thetectonic kind is by far the most devastating, and these earthquakes create many difficulties for scientists trying to develop waysto predict them. The main cause of tectonic earthquakes is stress set up by movements of the dozen major and minor platesthat make up the earths crust. Most tectonic quakes occur at the boundaries of these plates, in zones where one plate slidespast another, such as at the San Andreas Fault in California, North Americas most quake-prone area, or where one plateslides beneath the other plate, subduction. Subduction-zone earthquakes count for nearly half of the worlds destructive seismicevents and 75 percent of the earths seismic energy. They are concentrated along the Ring of Fire, a narrow band about38,600 km long, that meet with the border of the Pacific Ocean. The points at which rupture occurs in these earthquakes tendto be far below the earths surface, at depths of up to 645 km. Alaskas disastrous Good Friday earthquake of 1964 is anexample of one such event. Tectonic earthquakes beyond the Ring of Fire occur in a variety of geological settings. Mid-oceanridges, which are the seafloor-spreading centers of tectonic plates, are the sites of many events of moderate intensity that takeplace at relatively shallow depths. These quakes are seldom felt by anyone and account for only 5 percent of the earths seismicenergy, but they are recorded daily on the instruments of the worldwide network of seismological stations. Another setting fortectonic earthquakes is an area stretching across the Mediterranean and Caspian seas, and the Himalaya, ending in the Bay ofBengal. In this zone, which releases about 15 percent of the earths seismic energy, continental landmasses riding on theEurasian, African, and Australian plates are being forced together to produce high, and new mountain chains. The resultingearthquakes, which occ ur at shallow to intermediate depths, have often devastated areas of Portugal, Algeria, Morocco, Italy,Greece, the Former Yugoslav Republic of Macedonia, Turkey, and other countries partly or completely on the BalkanPeninsula, Iran, and India. Financial Instability EssayAttempts at predicting when and where earthquakes will occur have had some success in recent years. At this time China,Japan, Russia, and the U.S. are the countries most actively supporting this research. In 1975 the Chinese predicted themagnitude 7.3 earthquake at Haicheng, evacuating 90,000 people only two days before the earthquake destroyed or damaged90 percent of the citys buildings. One of the clues that led to this prediction was a chain of low-magnitude tremors, calledforeshocks, that had started about five years earlier in the area. Other potential clues being investigated are tilting or bulging ofthe land surface and changes in the earths magnetic field, in the water levels of wells, and even in animal behavior. A newmethod under study in the U.S. involves measuring the buildup of stress in the crust of the earth. On this idea of suchmeasurements the U.S. Geological Survey, in April 1985, predicted that an earthquake of magnitude 5.5 to 6 would occur onthe San Andreas fault, near Parkfield, California, sometime before 1993. Many unofficial predictions of earthquakes have alsobeen made. In 1990 a zoologist, Dr. Iben Browning, warned that a major earthquake would occur along the New Madrid faultbefore the end of the year. Like most predictions of this type, it was proved wrong. While I was trying to predict earthquakes, my first prediction wasnt too far off of my target, I predicted one about 100 milessouth of the California-Mexico border. There were a couple of earthquakes that occurred in California, near L.A, they were ofcourse very minor and couldnt be felt, they were only detectable by seismographs. The next day I predicted that there wasgoing to be an earthquake in the same spot that it occurred the day before. I was correct, in fact there were three. The nextday I picked a spot about 50 miles north of the earthquake that occurred the day before, this time I was wrong, there weretwo that occurred near the San Francisco bay area and none within a 50 mile radius of my approximation. The next coupledays I predicted earthquakes that were within a 100 mile radius than were they actually occurred. From my experiments Iconcluded that predicting earthquakes was easy, you just have to pick a spot on the fault. The only thing that troubled me andprobably most scientists, is magnitude, there is no possible way of predicting an earthquakes magnitude. Which is what we arereally trying to predict. Earthquakes happen all the time, but what we are really trying to figure out how to predict is when amajor earthquake is going to occur. I learned that earthquakes are almost unpredictable, and devastating acts of nature. I also learned how earthquakes occur andalmost all of the earthquake dictionary. There is still alot more to be known about earthquakes that we still do not knowabout today. Prediction of large earthquakes is still under development, where prediction of small, unnoticeable earthquakescan be easy to predict because they happen mainly around fault lines. Science