On the night of August 17, 1959, at about 20 minutes before midnight, the ground in the vicinity¹ of Yellowstone National Park began shaking violently. At the time there was a rumbling² sound, something like a huge truck would make. Both the heaving³ of the ground and the noise were very frightening but lasted not quite 45 seconds.

1959年8月17日的晚上，大约午夜前20分钟，黄石国家公园附近大地开始猛烈摇动。同时，大地发出如同重型卡车发出的轰响。大地的升降和 啸叫都令人非常害怕，但是一切不超过45秒。

What was even more frightening was the sound of huge boulders⁴ which began rolling down the steep mountain. In one part of the upper reaches of the Madison River, a whole mountain began shifting, then came crashing down to fill the deep valley and dam the great river with millions of tons rock and trees.

更令人害怕是巨石开始从陡峭的山上滚下来的声音。在麦迪生河上游 的一条支流处，一整座山开始移动，之后，它崩塌下来填满深深的山谷，上 百万吨岩石和大树如坝般阻挡住大河。

A dozen or more campers along the river were buried deep beneath the great landslide⁵. Others were able to climb to safety, some of them badly hurt, but were trapped by the slide. Finally these people were saved, many of them by helicopter.

十几个，或许更多沿河的露营者被深埋在大滑坡下。幸存的野营者开 始爬向较安全的地方，其中一些人伤得很重，仍然不时陷入滑坡。最后这些 人都获救了，其中很多人得救于直升飞机。

This earthquake near Yellowstone Park was just one of nearly a million that happen every year all over the world. And as bad as this quake was, many have been worse.

在黄石公园附近发生的地震，仅仅是每年全世界发生的上百万次地震 中的一次。若就地震灾害而论，有许多地震甚至更严重。

Earthquake experts say that the Yellowstone quake of 1959 was about as bad as the one which hit San Francisco in 1906. But the San Francisco quake caused more damage because it struck in a place where there were so many people living. In San Francisco 700 person lost their lives.

地震专家说，1959 年的黄石的地震，差不多相当于1906年发生在旧金山的地震。旧金山地震造成更多的破坏，它发生在人口密集地方。在旧金山约700人丧失生命。

An earthquake in Japan in 1923 took 160,000 lives. In China in 1920 an earthquake took 200,000 lives. It is easy to understand why earthquake are so feared.

1923 年发生在日本的地震夺走了16万人的生命。1920年一场大地震发生在中国， 20万人死亡。因此，很容易理解人们为什么非常恐惧地震。

What causes these terrible shakes of the very ground on which we live?

是什么原因造成我们生活的这块土地发生可怕的摇动?

To answer that question we must first understand some things about the earth itself.

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。

Forty miles deep in the earth is the edge of the outer crust of the earth, and there it is so hot that instead of hard rock there is material much like the hot lava⁶ that a volcano erupts.

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 物质代替了坚硬的岩石。

It is the earth's 40 mile deep crust with which we are concerned when we seek the cause of earthquake.

若我们寻求地震的起因，这40英里地壳恰恰是我们应该关心的地带。

The earth's crust is formed of many different layers of rocks. The layers of rocks are not laid evenly, as a bricklayer would build a wall. Instead, the earth's crust is made of rock layers that are often uneven⁷ and not perfectly⁸ balanced.

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。

Because of the great weight pressing down on them, these layers tend to fold downward at weak spots, and this finally causes an actual break in the crust. When this break occurs, or when the sides of an old break slip, the earth quakes, or shakes, while the crust is settling into a new position.

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—个新位置。

Sometime these faults are very small, and we then feel only little tremor⁹. 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 that which occurred in Madison Canyon¹⁰.

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。

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.

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—个大地震之后。有时这种情况要持续 多年。

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.

地球的某些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英里。

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, then closed, leaving no trace of those who perished¹¹. We know now this does not happen.

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。

What we need to fear most are the after-effects of a bad earthquake: fires, flood, and landslides¹².

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。

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.

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。

Even though earthquakes happen every day, an occurrence¹³ 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.

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。