Predicting Earthquakes
Can earthquakes be predicted? Scientists are working on programs to predict where and when an earthquake will occur. They hope to develop an early warning system that can be used to forecast earthquakes so that lives can be saved.
Earthquakes are the most dangerous and deadly or all natural events. They occur in many parts of the world. Giant earthquakes have been recorded in Iran, China, Guatemala, Chile, India, and Alaska. Two of the biggest earthquakes that were ever recorded took place in China and Alaska. These earthquakes measured about 8.5 on the Richter Scale. The Richter Scale was devised by Charles Richter in 1935, and compares the energy level of earthquakes. An earthquake that measures a 2 on the scale can be felt but causes little damage. One that measures 4.5 on the scale can cause slight damage, and an earthquake that has a reading of over 7 can cause major damage. It is important to note that a reading of 4 indicates an earthquake ten times as strong as one with a reading of 3. Scientists want to be able to predict those earthquakes that have a reading of over 4 on the Richter Scale.
How do earthquakes occur? Earthquakes are caused by the shifting of rocks along cracks, or faults, in the earth's crust. The fault is produced when rocks near each other are pulled in different directions. The best-known fault in North America is the San Andreas fault in the state of California in the United States.
The nations that are actively involved in earthquake prediction programs include Japan, China, Russia, and the United States. These countries have set up seismic networks in areas of their countries where earthquakes are known to occur. These networks are on the alert for warning signs that show the weakening of rock layers that can precede an earthquake. Many kinds of seismic instruments are used by the networks to monitor the movements of the earth's crust. The scientists also check water in deep wells. They watch for changes in the water level and temperature that are associated with movement along faults.
Scientists in China, Russia, and the United States measure radon in ground water. Radon is a gas that comes from the radioactive decay of radium in rocks. The gas flows through the ground and dissolves in underground streams and wells. Scientists speculate that the amount of radon increases in the ground when rocks layers shift, exposing new rock, and thus more radon.Chinese and Russian scientists have reported that in places where stress is building up, the radon levels of the water build up too. When the radon levels of the water subside and drop back to normal readings, an earthquake may occur. United States scientists have also placed radon monitoring stations in earthquake zones, particularly California. However, all the scientists agree that more data is necessary to prove that radon levels in water are associated with the possible birth of an earthquake.
Earthquake prediction is still a young science. Everyone agrees that earthquakes cannot be predicted with any reliability. Scientists have only a partial understanding of the physical processes that cause earthquakes. Much more research has to be done. New and more up to-date methods have to be found for collecting earthquake data and analyzing it. However, scientists have had some success in predicting earthquakes. Several small earthquakes were predicted in New York State, in the eastern part of the United States. Chinese scientists predicted a major one in Haicheng in 1975, and Russian scientists predicted a major one in Garm in 1978. While this is a small start, it is still a beginning.
译文：
预测地震
地震可以预报吗？科学家们正致力于研究预报何时何地会发生地震的计划，他们希望开发一种早期报警系统用来预报地震，以挽救人们的生命。
地震是自然灾害中最危险的最致命的，发生在世界许多地方。伊朗、中国、危地马拉、智利、印度和阿拉斯加都有过大地震的记录。有记载的最大两次地震是发生在中国和阿拉斯加。这两次地震经测量约为里氏8.5级。里氏震级是1935年查尔斯·里克特发明的，用来比较地震的能量等级。里氏地震级测出的2级地震可以感觉到，但几乎没什么破坏；测出的4.5级地震能够造成轻微破坏，读数超过7级的地震会带来重大破坏。必须注意的是，读数为4级的地震表明其强度是读数为3级的10倍。科学家想预测那些读数超过里氏4级的地震。
地震是怎么发生的呢？地震是由地壳中的裂缝，或称断层处的岩石发生移位而引起的。当邻近岩石受到不同方向的拉力时便产生了断层。北美洲最著名的断层是位于美国加利福尼亚的圣安德烈亚斯断层。
积极参与地震预测计划的国家包括日本、中国、俄罗斯和美国。这些国家在已知发生地震的地区建立了地震网络，这些网络一直处于戒备状态，搜索着告警的迹象，这些迹象显示出在地震前可能发生的岩层松动的状况。这些网络使用多种地震仪器来监测地壳的运动。科学家还检查深井里的水，观察与断层运动有关的水位与温度的变化。
中国、俄罗斯和美国的科学家测量地下水的氡含量。氡是来自岩石中镭辐射衰变而产生的气体。这种气体溢出地面并溶解到地下溪流和井里。科学家推测当岩层移位时，新岩石露出，产生更多的氮，这样地层中的氡数量就增加了。中国和俄罗斯报告说压力增加的地方，水中氡的含量也会增加。当水中氡的含量下降，回到正常读数时，地震就可能发生。美国科学家也在地震区，特别是加利福尼亚，设置了检测站。不过，所有的科学家都一致认为，需要更多的资料才能证明水中氡的含量和可能发生的地震有关。
地震预测仍然是一门年轻的科学。人们都认为地震不可能可靠地预测。科学家对引起地震的物理过程只是部分了解，还必须作更多的研究，必须找到新的和更先进的方法收集地震数据并加以分析。不过，科学家已经在地震预测方面取得了一些成功：美国东部纽约州的几次小地震就已预测到了，1975年中国科学家预测到了海城大地震，1978年俄罗斯科学家预测了加尔姆大地震。虽然这只是个小小的起步，但毕竟是一个开端
课文讲解：
一、单词讲解：
1.work on 从事（某工作），对。。。施加影响，对。。。起作用
例如：
He sat up far into the night working on the document .
She worked on her friends to help her.
2.warning 警告、前车之鉴：
She ignored the policeman’s warning.
3. forecast:
1)预报、预言:
The teacher forecast that 15 of his students would pass the examination.
2) 预报、预言n.
The weather forecast on the radio tonight tells of coming storm.
4. indicate指明、表明、说明：
Indicate where the pain is with your finger.
If you put up your hand it will indicate that you agree with me.
5.associate把。。。和。。。连接起来、和。。。往来、 和。。。共事：
I don’t associate the two ideas.
6.dissolve 融解、分解、消失、解散、解除：
Salt dissolves in water.
7.speculate 思考、思索、作投机买卖：
I’ve been speculating on my future.
8.build up:建设起来、发展起来、加强（力量）、增强（体质）、积累、集聚、逐步增加、盖满房子（用于被动语态）
例如：
The area has been built up since I lived here 从我住这里起，这里盖满了房子
He has built up a good business over the years
课文解释：
1.They hope to develop an early warning system that can be used to forecast earthquakes so that lives can be saved. 他们希望开发一种早期报警系统，用来预报地震，以挽救人们的生命。
1） 本句含有so that引导的目的状语从句。如果主句是一般现在时，从句常用may或can,如果主句时一般过去时，从句常用could, should 或might.例如： He wrote her a long letter to clarify the fact so that she would not misunderstand him 他写了一封长信说明事实真相，以便不使她误会。
2） 主句中动词不定式短语to develop an early warning system that can be used to forecast earthquakes 作hope的宾语，其中that can be used to forecast earthquakes 是定语从句，修饰system.
2. These networks are on the alert for warning signs that show the weakening of rock layers that can precede an earthquake.这些网络一直处于戒备状态，搜索着报警的迹象，这些迹象显示出在地震前可能发生的岩层松动的状况。
1） 本句中是含有双重定语从句的复合句。That show the weakening of rock layers that can precede an earthquake修饰warning signs,而that can precede an earthquake 又修饰the weakening of rock layers.
2） on the alert 意为：“处于警惕状态”例如： Drivers must be on the alert for traffic signals.
3. Scientists speculate that the amount of radon increases in the ground when rocks layers shift., exposing new rock, and thus more radon.科学家推测当岩层移位时，新岩石露出，产生更多的氡，这样地层中的氡的数量就增加了。
1） 本句中的主句是：Scientists speculate that the amount of radon increases in the ground，主句中的that the amount of radon increases是宾语从句。
2） when racks layers shift是时间状语从句。
3） 现在分词短语exposing new rock, and thus more radon作伴随状语。
4．While this is a small start, it is still a beginning虽然这只是一个小小的起步，但毕竟是一个开端。
本句是由while引导的让步状语从句，突出对比主句和从句所表示的两种差异的情况。例如： He is experienced while he is young 他虽然年轻，但却很有经验。
补充材料：
一、不用倒装的十种情况：
在英语中，为了加强语气或某些句子结构的需要，要采用倒装语序。但是，当出现以下情况时，则不用倒装语序，而用陈述语序。
1．以here，there，up，down，away， in，out等副词开头的句子，若主语为人称代词时。如：
Here he is．他来了。
Away she went．她走了。
2．当疑问代词及其所构成的短语在句子中作主语时。如：
Whos on duty today？今天谁值日？
Whats in the bag？包里有什么？
3．若直接引语后注明引语是何人说的，且主语为代词时。如：
“Lets go！”he said．他说：“咱们走！”
4．若only后强调的不是状语，而是主语时。如：
only Lucy knows this．只有露西知道此事。
5．若so提前，为了对上述情况加以强调、肯定，构成“so＋主语＋谓语”结构时。如：
—He is a student．他是一名学生。
—So he is．他的确是（确实如此）。
6．当两个分句的主语或谓语不一致时，或两个分句的谓语动词分别是肯定或否定时，若表示“某人也是如此”时，用：So it is ／ was with sb．如：
I came to Heilongjiang，Heilongjiang was my hometown． So it was with my wife．我来到黑龙江，黑龙江是我的故乡，我妻子也是如此。
7．为了强调，把宾语移至句首时。如：
This book I will keep for myself．这本书为我所有。
8．在名词性从句中，如宾语从句中等。如：
I don't know when he came here．我不知道他什么时候来这儿的。
When they will leave here is unknown．他们将什么时候离开无人知晓。
9．当疑问句为双重疑问句时。如：
What do you know it is made up of？你知道它是由什么构成的？
10．当not only．．．But also， neither．．．Nor连接主语时，虽位于句首也不用倒装。如：
Not only I but also she likes English．不仅我而且她也喜欢英语。
二、补充语序讲义
一、跟在及物动词后的由连接副词或连接代词how，when，where，why，who，which，whom， what，whose以及whether，if 引导的宾语从句要用陈述句语序，即主语、谓语不必颠倒。例如：
I cant describe what I felt at that moment．
Could you tell me why many writers are not fully appreciated until long after they die？
二、在以think，believe，suppose，expect等动词引起的宾语从句中，尽管从句表示否定意义，一般却是通过否定主句的谓语动词来否定从句。例如：
Don't expect that he will come here in time next Sunday．
I don't believe that they could finish the work within this week．
三、由as引导的让步状语从句，常常用部分倒装。例如：
Young as he is，he is excellent in his work．
Poor health as she has，she insists on working hard in her post．
四、句首为带有否定意义的词或词组时，常用部分倒装。
这类词或词组有：hardly，little，never，not until，no sooner，at no time，by no means，in／ under no circumstances，in vain，no longer，not often等。例如：
Under no circumstances should we do anything that will benefit ourselves but harm the interests of the state．
Not only is he a talented president of a university，but also he is open-minded．
否定副词如果放在句首只是限定主语而非修饰全句，则句子不必倒装。例如：
No survivor has yet been found．
五、有些表示程度的副词或短语作状语而又置于句首时，句子用部分倒装表示强调。这类词或词组有：so．．．That，to such an extent，to such a degree，to such extremes等。例如：
So hard does she study that all her teachers like her．
So late was he for the class that the teacher criticized him．
六、句首为“only ＋状语”时，常用部分倒装。例如：
only by changing your working style can you be accepted by your colleagues．
Only then did I realize how childish I was in hoping him to change his habit．
七、在比较和方式状语从句中，如果主语不是人称代词，常可在主语前添加助动词或系动词代替前面出现过的动词，形成一种部分倒装的形式。例如：
The standard of living of the people in our country now is much higher than was the case ten years ago．
I spent more time on practicing my oral English than did most of my classmates when I was at college．
八、在含虚拟语气的条件句中，如果if被省略，那么were，had或should要移至主语之前。例如：
Were there no gravity，there would be no air around the earth．
Should anyone come to our home to sell things，don't let him ／her in．
另外，在一些感叹句和某些表示祝愿的句子里，已形成一种固定结构的倒装表达法。例如：
How wonderful is the fashion show！
Long live our friendship！
九、hardly，barely，scarcely和when连用以及no sooner和than连用时，形成固定的倒装结构，表示一件事紧接着另一件事发生，意为“一……就……”。在时态上，主句一般用过去完成时，而从句用过去时。例如：
Scarcely had I left home for school，when it began to rain heavily．
Hardly had I put down the phone，when the phone rang again．
No sooner had the result of the appointment of some leader positions turned out，than came some rejections. |
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