A、Because the waves coming from the center of a quake can spread to these places. B、Because there are the thickness of rocks mak

Some parts of the earth are more likely to have quakes than others. This is usually true of mountain areas, because there the thickness of rocks, which make up the earth’s crust, is not even. But quakes may often be felt in level regions, too, because the waves, which come from the center of a quake, run often for thousands of miles.
    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, and those who were killed disappeared forever. We know now this does not happen.
    What we need to fear are the after-effects of a serious earthquake: fires, floods, 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 occurring after the earthquake. This is, actually a foolish idea. Such a fear would keep us away from mountains the rest of our lives. Even though earthquakes happen every day something like the Madison River landslide does not happen very often. We can realize gratefully that few of us will suffer because of such a disaster. At the same time we can understand the need of being ready to help those who do suffer such trouble.