背景知識資料分享~P波 S波 - 英檢

前幾天閱讀考了地震波
(以前好像也有考過聽力)
而今年年初因為海地地震
CNN也介紹了P波S波

對地震波完全沒概念的同學
可以看看CNN主播怎麼介紹地震波
(只有前面不到三分半鐘,很短)
看完介紹應該可以知道S波為什麼這麼恐怖
希望對大家有幫助

http://0rz.tw/VQepd

以下是聽力原文,網頁上也有

JENNY HARRISON, CNN INTERNATIONAL WEATHER ANCHOR: Let me just show you where we are talking about. Here is the fault line. And of course, straightaway, you can see how close to that Port-au-Prince is. There's the epicenter close, as well, to Carrefour. This is the fault we're talking about. Now, this is what is called a strike-slip earthquake, and literally this is what happens. You have the two plates rubbing up against each other. That friction is building, it is building, it is building, and
eventually something has to happen.

Now, when you have an area that sees many, many earthquakes over whatever period of time, well, then what actually happens is that a lot of that pressure or that friction is actually released periodically, so you don't get this massive buildup of friction, which is exactly what happened here.

The deeper down, of course, as you can well imagine, by the time the waves actually reach the surface, those shockwaves, you barely feel it. The closer to the earth's surface, then the more shocking it will be; the more impact it is going to have. And again, the distance that you are from the epicenter plays a part, as well as the depth in the earth.

Now, also what happened here, was that the epicenter of the quake was well inside the mountains. Very, very dense; much less shaking. But again, once it headed out and was pushing out towards the coast, that's when it began to be felt. Much less dense.

Now, at the same time, of course, it couldn't have happened in a worse place because of the population. This gives you an idea of the population of Haiti. And of course, the gray blocks trying to illustrate the intensity of populations. So, the two most densely populated cities, of course, the capital Port-au-Prince and also Carrefour. The violent shaking was felt dramatically all around that area.

Now, first of all, you have what is called a primary wave, and this moves everything, obviously, very violently, but can sometimes be over fairly quickly. This is then followed by the S-wave, the secondary waves, of which there could be numerous. We've had numerous aftershocks reported. And you can see what happens. It's called that for a reason: it moves in an S shape. It moves vertically or horizontally. When it moves vertically, this is when we see the most damage, because this is when we see the tops
of the buildings coming off like the presidential palace. Literally, it is just shaken off the roots of its foundations.



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