大学六级-473及答案解析.doc
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1、大学六级-473 及答案解析(总分:703.00,做题时间:90 分钟)一、BPart Writing(总题数:1,分数:106.00)1.1近年来,各类培训班如雨后春笋不断涌现,很多大学生报名参加各类培训; 2很多人认为参加培训班有诸多好处 3你的观点。(分数:106.00)_二、BPart Reading (总题数:1,分数:70.00)Directions: In this part, you will have 15 minutes to go over the passage quickly and answer the questions on Answer Sheet 1.For
2、 questions 1-4, mark Y (for YES) if the statement agrees with the information given in the passage; N (for NO) if the statement contradicts the information given in the passage; NG (for NOT GIVEN) if the information is not given in the passage. For questions 5-10, complete the sentences with the inf
3、ormation given in the passage. TsunamiUp until December of 2004, the phenomena of tsunami was not on the minds of most of the worlds population. That changed on the morning of December 24, 2004 when an earthquake of moment magnitude 9.1 occurred along the oceanic trench off the coast of Sumatra in I
4、ndonesia. This large earthquake resulted in vertical displacement of the sea floor and generated a tsunami that eventually killed 280,000 people and affected the lives of several million people. Although people living on the coastline near the epicenter of the earthquake had little time or warning o
5、f the approaching tsunami, those living farther away along the coasts of Thailand, Sri Lanka, India, and East Africa had plenty of time to move to higher ground to escape. But, there was no tsunami warning system in place in the Indian Ocean, and although other tsunami warning centers attempted to p
6、rovide a warning, there was no effective communication system in place. Unfortunately, it has taken a disaster of great magnitude to point out the failings of the worlds scientific community and to educate almost every person on the planet about tsunami. How Tsunamis Are Generated There is an averag
7、e of two destructive tsunamis per year in the Pacific basin. Pacific wide tsunamis are a rare phenomenon, occurring every 10-12 years on the average. Most of these tsunamis are generated by earthquakes that cause displacement of the seafloor. Earthquakes cause tsunami by causing a disturbance of the
8、 seafloor. Thus, earthquakes that occur along coastlines or anywhere beneath the oceans can generate tsunami. The size of the tsunami is usually related to the size of the earthquake, with larger tsunami generated by larger earthquakes. But the sense of displacement is also important. Tsunamis are g
9、enerally only formed when an earthquake causes vertical displacement of the seafloor. The 1906 earthquake near San Francisco California had a Richter Magnitude of about 7.1, yet no tsunami was generated because the motion on the fault (断层) was strike-slip motion with no vertical displacement. Thus,
10、tsunami only occur if the fault generating the earthquake has normal or reverse displacement. Because of this, most tsunamis are generated by earthquakes that occur along the subduction boundaries of plates, along the oceanic trenches. Since the Pacific Ocean is surrounded by plate boundaries of thi
11、s type, tsunamis are frequently generated by earthquakes around the margins of the Pacific Ocean. BExamples of Tsunami Generated by Earthquakes /BMay 22, 1960-A moment magnitude 9.5 earthquake occurred along the subduction zone off South America. Because the population of Chile is familiar with eart
12、hquakes and potential tsunami, most people along the coast moved to higher ground. 15 minutes after the earthquake, a tsunami with a run-up of 4.5 m hit the coast. The first wave then retreated, dragging broken houses and boats back into the ocean. Many people saw this smooth retreat of the sea as a
13、 sign they could ride their boats out to sea and recover some of the property swept away, by the first wave. But, about 1 hour later, the second wave traveling at a velocity of 166 km/hr crashed in with a run-up of 8 m. This wave crushed boats along the coast and destroyed coastal buildings. This wa
14、s followed by a third wave traveling at only 83 km/hr that crashed in later with a run-up of 11 m, destroying all that was left of coastal villages. The resulting causalities listed 909 dead with 834 missing. In Hawaii, a tsunami warning system was in place and the tsunami was expected to arrive at
15、9:57 AM. It hit at 9:58 AM and 61 people died, mostly sightseers that wanted to watch the wave roll in at close range (obviously they were too close). The tsunami continued across the Pacific Ocean, eventually reaching Japan where it killed an additional 185 people. Prediction and Early Warning For
16、areas located at great distances from earthquakes that could potentially generate a tsunami there, is usually plenty of time for warnings to be sent and coastal areas evacuated, even though tsunami travels at high velocities across the oceans. Hawaii is a good example of an area located far from mos
17、t of the sources of tsunami, where early warning is possible and has saved lives. For earthquakes occurring anywhere on the subduction margins of the Pacific Ocean there is a minimum of 4 hours of warning before a tsunami would strike any of the Hawaiian Islands. The National Oceanic and Atmospheric
18、 Administration (NOAA) has set up a Pacific warning system for areas in the Pacific Ocean, called the Pacific Tsunami Warning Center. It consists of an international network of seismographic stations, and tidal stations around the Pacific basin that can all send information via satellite to the Cent
19、er located in Hawaii. When an earthquake occurs somewhere in the region, the Center immediately begins to analyze the data looking for signs that the earthquake could have generated a tsunami. The tidal stations are also monitored, and if a tsunami is detected, a warning is sent out to all areas on
20、the Pacific coast. It takes at least 1 hour to assimilate all of the information and issue a warning. Thus for an average velocity of a tsunami of 750 km/hr, the regional system can provide a warning sufficient for adequate evacuation of coastal areas within 750 km of the earthquake. In order to be
21、able to issue warnings about tsunami generated within 100 to 750 km of an earthquake, several regional warning centers have been set up in areas prone to tsunami generating earthquakes. These include centers in Japan, Kamchatka, Alaska, Hawaii, French Polynesia, and Chile. These systems have been ve
22、ry successful at saving lives. For example, before the Japanese warning system was established, 14 tsunamis killed over 6000 people in Japan. Since the establishment of the warning system 20 tsunamis have killed 215 people in Japan. Tsunami Safety Rules A strong earthquake felt in a low-lying coasta
23、l area is a natural warning of possible, immediate danger. Keep calm and quickly move to higher ground away from the coast. A tsunami is not a single wave, but a series of waves. Stay out of danger until an “ALL CLEAR“ is issued by a competent authority. Approaching tsunamis are sometimes heralded b
24、y noticeable rise or fall of coastal waters. This is natures tsunami warning and should be heeded. A small tsunami at one beach can be a giant a few miles away. Do not let modest size of one make you lose respect for all. Never go down to the beach to watch for a tsunami? WHEN YOU CAN SEE THE WAVE Y
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