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Eastern Quakes Can Trigger Big Shakes

In the first week of November 2011，people in central Oklahoma experienced more than two dozen earthquakes. The largest,a magnitude（量）5.6 quake,shook thousands of fans in a college football stadium,caused cracks in a few buildings and scared many people who had never felt a quake before. Oklahoma is not an area of the country famous for its quakes. If you watch the news on TV,you see reports about all sorts of natural disasters. But the most dangerous type of natural disaster,and also the most unpredictable,is the earthquake.

Researchers at the US Geological Survey（USGS）estimate that several million earthquakes occur globally each year. That may sound scary,but people don't feel many of them because they happen in remote and unpopulated regions. Many quakes happen under the ocean,and others have a very small magnitude.

Scientists know about small,remote quakes only because of very sensitive electronic devices called seismometers（地震仪）。 These devices detect and measure the size of ground vibrations（震颤）produced by earthquakes. Altogether,USGS researchers use seismometers to identify and locate about 20000 earthquakes each year.

Although earthquakes can happen anywhere in the world,really big quakes occur only in certain areas. The largest ones register a magnitude 8 or higher and happen,on average,only once each year. Such big ones typically occur along the edges of Earth's tectonic plates（构造板块）.a

Thctonic plates are huge pieces of Earth's crust（外壳）,sometimes many kilometers thick. Often,edges of these plates temporarily lock together. When plates push and scrape（擦）past each other earthquakes occur. On average,tectonic plates move very slowly——bout the same speed as your fingernails grow.

But sometimes earthquakes rumble（轰轰作响）through portions of the landscape far from a plate's edges. Although less expected,these"mid-plate"small earthquakes can be stantial damage. Some of the biggest known examples hit the eastern half of the United States two centuries ago. Today,scientists are still puzzling over why the quakes occurred and when similar ones might occur.

16. Oklahoma is an area often experiencing natural disasters.

A. Right

B.Wrong

C.Not mentioned

[参考答案]B

[解析]题意：俄克拉荷马是一个经常遇到自然灾害的地区。

关键词为0ften，经常。根据文中的Oklahoma is not an area of the country famous for its auakes. If you watch the news on TV，you see reports about all sorts of natural disasters一hurricanes，torna— does，flooding and wildfires，to name a few可知俄克拉荷马并不因地震而闻名，其他类型的灾难也很少在电视上看到，由此可判断奥克拉荷马并不受灾难的眷顾。故选B.

17. The earthquake is the most unpredictable natural disaster.

A. Right

B.Wrong

C.Not mentioned

[参考答案]A

[解析]题意：地震是最不可预测的自然灾害。

根据文中第一段最后一句But the most dangerous type of natural disaster，and also the most un-

predictable，is the earthquake可知，地震是最难预测的自然灾难。故选A.

18. Few earthquakes happen without people's awareness.

A. Right

B.Wrong

C.Not mentioned

[参考答案]B

[解析]题意：人们能感觉到几乎所有的地震。

关键字是few.few是几乎没有的意思，表否定，与a few不同。文中第二段第二句……but people don't feel many of the tremors because they happen in remote and unpopulated regions说明，在人迹罕至的地区发生的地震，人们是感觉不到的。故选B.

19. Seismometers can identify and locate most of the earthquakes in China.

A. Right

B.Wrong

C.Not mentioned

[参考答案]C

[解析]题意：地震仪能确认和定位中国的很多地震。

文中并未提及中国。故选C.

20. Big earthquakes of a magnitude 8 or higher seldom happen far from the edges of tectonic plates.

A. Right

B.Wrong

C.Not mentioned

[参考答案]A

[解析]题意：八级或以上的地震基本上都发生在板块边缘。

关键字seldom，这也是一个表否定的词汇。文中第五段第二、三句The largest Ones register a magnitude 8 0r higher and happen，on average，only once each year.Such big ones typically occur a— long the edges of Earth's tectonic plates明确指出，八级或更大的地震一般发生在地壳板块边缘。故选A.

21. Whenever tectonic plates move,earthquakes happen.

A. Right

B.Wrong

C.Not mentioned

[参考答案]B

[解析]题意：当板块移动时就会发生地震。

根据文中第六段倒数第二句When plates jostle and scrape past each other earthquakes occur可知，板块互相挤压时才会发生地震，而不是板块一动就地震。故选B.

22. The earthquake that hit the eastern half of the United States two centuries ago is the biggest“mid-plate"one in history.

A. Right

B.Wrong

C.Not mentioned

[参考答案]C

[解析]题意：200多年前袭击美国东半部的地震是最大的板块中间类型的地震。

文中并未提及200多年前袭击美国东半部的地震是最大的板块中间类型的地震。故选C.