6、要回答这个问题,必须首先要了解关于地球自身的某些事物。地表面下40英里深,是地球外壳的边缘,此处非常之热,如同火山喷出的岩浆般的物质替代了坚硬的岩石。若我们寻求地震的原因,这40英里地壳恰恰是我们应该关心的地带。地壳由很多不同岩石层构成。而岩层并不像建筑工人建的墙一样均匀地平整铺开,相反的,岩层构成的地壳也往往是不均匀且不是完美平衡的。由于巨大重量向下压岩层,使它趋于在它的薄弱点处往下折叠,这最后将造成地壳里的某处断裂。当断裂发生时,或者旧的断裂块滑动时,地球震动、摇动,以使地壳安排它进入一个新位置。
   7. Sometime these faults are very small, and we then feel only little tremor. The tremor may even be so light that only the most delicate machine will record it. Most earthquakes are of this weak kind. Sometimes a break in the earth's crust comes about, which starts such a landslide as the which occurred in Madison Canyon. It then takes not one, but many shakes for the earth to heal the fault and settle. That is why many after-shocks follow a major earthquake. Sometimes these go on for several years.
   7、有些时候这些断裂非常小,我们仅仅能感到微小的颤动。这种颤动甚至轻到最精密的设备才可能记录它们。大多数地震属于这种类型。也有些时候地壳的一个断裂发生了,引起如同在麦迪生峡谷发生的大滑坡。这种大地震往往不是一次,而是很多次的移动,使地球去修补裂缝和调整(岩层的)姿态。这就是为什么很多余震紧跟在一个大地震之后。有时这种情况要持续多年。
   8. Some Parts of the earth are more likely to have quakes then others. This is usually true of mountainous country, because there the layers of rocks which make up the earth's crust are not at all even. But quakes may often be felt in level country, too, because the waves which come from the center of a quake run often for thousands of miles.
   8、地球的某部分比其它部分更容易发生地震。山地国家往往这样。山地区域构成地壳的岩层特别不均匀。但是,平原国家也会经常感觉到地震,因为从震源发出的震波往往可以传出上千里。
   9. It is easy to understand why man is so frightened by an earthquake. People used to think that when there was an earthquake, the ground opened, swallowed great numbers of people, and then closed, leaving no trace of those who perished. We know now this does not happen.
   9、很容易理解为什么人特别害怕地震。人们过去认为,当某个地方发生了地震,即大地裂开,吞下大量的人,然后又合上,人们被不留痕迹地毁灭。现在我们知道这一切从来不曾发生。
   10. What we need to fear most are the after-effects of a bad earthquake: fires, flood, and landslides. Since the Yellowstone earthquake some people have said that they would never go to that area for fear of being caught in a landslide such as occurred after the earthquake. That is foolish. Such a fear would keep us from mountains the rest of our lives. Even though earthquakes happen every day, an occurrence like the Madison River landslide does not happen very often. We can realize gratefully that few of us will suffer because of such disaster. At the same time we can understand the need of being ready to help those who do suffer such trouble.
   10、实际上我们需要更多担心的是一个大地震的震后影响:火灾、洪水、和滑坡。自从黄石地震后,一些人说,他们因为害怕被发生在地震后的大滑坡伤害,再也不会去那个地方。这是愚蠢的。这种恐惧将使我们终生远离大山。尽管地震每天都在发生,像麦迪生河大滑坡似的事件却不是经常发生。我们能够意识到,只有我们中的极少数可能受到地震灾害的伤害。同时,我们也能理解,遭受那种灾害伤害的人正需要其它人的帮助。