Sunday, August 18, 2019
earthquake Essays -- essays research papers
Earthquakes have plagued our lives for as long as people have inhabited the earth. These dangerous acts of the earth have been the cause of many deaths in the past century. So what can be done about these violent eruptions that take place nearly with out warning? Predicting an earthquake until now has almost been technologically impossible. With improvements in technology, lives have been saved and many more will. All that remains is to research what takes place before, during, and after an earthquake. This has been done for years to the point now that a successful earthquake prediction was made and was accurate. This paper will discuss a little about earthquakes in general and then about how predictions are made. Earthquake, Ã¢â¬Å"vibrations produced in the earth's crust when rocks in which elastic strain has been building up suddenly rupture, and then rebound.Ã¢â¬ (Associated Press 1993) The vibrations can range from barely noticeable to catastrophically destructive. Six kinds of shock waves are generated in the process. Two are classified as body waves-that is, they travel through the earth's interior-and the other four are surface waves. The waves are further differentiated by the kinds of motions they impart to rock particles. Primary or compressional waves (P waves) send particles oscillating back and forth in the same direction as the waves are traveling, whereas secondary or transverse shear waves (S waves) impart vibrations perpendicular to their direction of travel. P waves always travel at higher velocities than S waves, so whenever an earthquake occurs, P waves are the first to arrive and to be recorded at geophysical research stations worldwide.(Associated Press 1993) Earthquake waves were observed in this and other ways for centuries, but more scientific theories as to the causes of quakes were not proposed until modern times. One such concept was advanced in 1859 by the Irish engineer Robert Mallet. Perhaps drawing on his knowledge of the str ength and behavior of construction materials subjected to strain, Mallet proposed that earthquakes occurred Ã¢â¬Å"either by sudden flexure and constraint of the elastic materials forming a portion of the earth's crust or by their giving way and becoming fractured.Ã¢â¬ (Butler 1995) Later, in the 1870s, the English geologist John Milne devised a forerunner of today's earthquake-recording device, or seismograph. A simple pen... ... warned that a major quake would occur along the New Madrid fault before the end of the year. Like most predictions of this type, it proved to be wrong. Ã¢â¬Å"Groundwater has also played an important part in earthquake predictions. A peak in radon in the groundwater at Kobe, Japan 9 days before the 7.2 earthquake cause quite a stir. Radon levels peaked 9 days before the quake, then fell below the normal levels 5 days before it hit.Ã¢â¬ (Monastersky July, 95) In North America, the series of earthquakes that struck southeastern Missouri in 1811-12 were probably the most powerful experienced in the United States in historical time. The most famous U.S. earthquake, however, was the one that shook the San Francisco area in 1906, causing extensive damage and taking about 700 lives.(Nagorka 1989) The whole idea behind earthquake predicting is to save lives. With the improvement in technology, lives have been saved. New ideas and equipment is starting to prove to be very helpful in pr edicting were and when an earthquake will strike. The time and research put into earthquake predicting has already started to pay off. It is only a matter of time before earthquakes will no longer be a threat to us.