Earthquakes
This is an excerpt from the paper...
At 5:04 on the afternoon of October 17, 1989, an earthquake, without warning, struck Loma Prieta, California (60 miles south of San Francisco), lasted for six to ten seconds, killed 63 people, injured 3,757 others, caused $6 billion in damages, registered 6.9 to 7.1 on the Richter scale, and produced 6,000 aftershocks. The Loma Prieta landscape came to life when subsurface tension in one of the shifting chunks of earth's crust, the Pacific Plate, snapped beneath the San Andreas fault line. Satellite observations show that the Pacific Plate- southwest of the San Andreas fault line- slipped more than six feet closer to the North Pole, relative to the North American Plate northeast of the fault. In comparison, the 1906 San Francisco earthquake had an average slip of 15 feet over almost 300 miles of the fault line, had released about 50 times more energy, and had lasted almost 80 seconds. In theory, the Bay Area should not have been so badly shaken because the epicenter was more than 100 kilometers away, and the seismic waves should have weakened considerably as they spread away from the source. The secret of Loma Prieta's long reach, however, is believed to lie deep in the crust, where Loma Prieta's waves were focused on San Francisco by deep crustal layers acting like mirrors. It is believed that the deep crusts near the epicenter could have efficiently reflected seismic waves from the event back toward the surface. Key to the reflection process would have been the layers of
. . .
ese weights to a rod going deep into the earth's crust assures the seismologists that only earthquake vibrations will make it move. Their study of vibrations indicate there are three kinds: surface waves (which move along the surface of the earth), P (Pressure) waves and S (Shear) waves, which move right through the earth. P waves vibrate back and forth in the direction it is traveling, and S waves vibrate sideways (or perpendicular) to the way it is traveling. P waves, travelling faster, are the first detected by seismologists. The farther the seismograph is from the earthquake, the longer will be the time between the arrival of P and S waves, which, in turn, are used to determine how far away, but not the direction, the epicenter (or origin) of the earthquake is.
Two systems measure earthquakes: the Mercali scale and the Richter scale, which many experts consider more accurate. The Richter scale starts at zero and goes as high as the earthquake dictates- each number representing an earthquake ten times as powerful as the number below it. To date, no earthquake higher than 9.0 has been detected. The most common method of predicting earthquakes (the where not he when)is the seismic gap method, which is based on pressure measure
. . .
Some common words found in the essay are:
Loma Prieta, San Francisco, Honshu Hokkaido, Southern Armenia's, Fever Newsweek, San Andreas, South America, Quake Science, Kong Zealand, Mental Health, loma prieta, san francisco, andreas fault, san andreas fault, san andreas, science 15, 15 december, science 15 december, october 1989, north american, sharp shock science, sharp shock, prieta saved short, bay mud, short sharp shock,
Approximate Word count = 3490
Approximate Pages = 14 (250 words per page)
More Essays on Earthquakes
|
Customer Service
to Over
32,000 Professionally Written Papers!!!
