问题
选择题
纵波（P波）和横波（S波）的传播速度在莫霍面以下发生的显著变化是
A．都明显下降
B．都明显增加
C．S波完全消失、P波突然下降
D．P波完全消失、S波突然下降
答案
答案：B
本题考查地震波传播速度的变化。通过莫霍界面，纵波和横波的速度都明显加快，经过古登堡界面，纵波速度减弱，横波消失。
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纵波（P波）和横波（S波）的传播速度在莫霍面以下发生的显著变化是
A．都明显下降
B．都明显增加
C．S波完全消失、P波突然下降
D．P波完全消失、S波突然下降
答案：B
本题考查地震波传播速度的变化。通过莫霍界面，纵波和横波的速度都明显加快，经过古登堡界面，纵波速度减弱，横波消失。
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| Steve and Mark were good friends. They decided to spend their vacation in Haiti. Since they 1 no French, they took a French word book with them and hoped it would help them in difficult situations. The flight was 2 , and the hotel was very comfortable. Each day after breakfast, Steve and Mark 3 a picnic lunch and dinner and went off to visit interesting places. After a while, the boys became tired of 4 picnic meals and decided to eat a big fish dinner in a good restaurant. Unfortunately, they 5 their word book in the hotel. They 6 the menu carefully. After ten minutes, Steve said to Mark: "I don't understand this menu." "Neither do I," said Mark. "I see poison on this menu. Are they 7 here?" "Maybe. They even spelled poison 8 . They spelled it p- o-s-s-o-n instead of p-o-i-s-o-n. But it 9 mean the same thing. Maybe we should go to another restaurant. I don't 10 to eat something that will kill me." But Mark was 11 , so he said:"There is no other restaurant near here, and I'm tired of walking around the city. Let's order something else instead. It's 12 here, so the food must be good. "The boys looked at the menu again. They finally decided to order steak, 13 they really wanted fish. The boys just pointed to the word steak, and the waiter 14 . As they were eating they 15 some tourists speaking English. "This 16 is delicious." "We're lucky we picked a restaurant that's famous for its fish." Steve and Mark wondered about what they 17 . "Famous for its fish? There was no fish on 18 !" said Mark. Finally, Steve decided to find out what all this was about. "Excuse me, how did you order fish when it wasn't on the menu?" "Sure it's on the menu. It's right here. Poisson." The boy shouted: "Poisson. That's 19 ! We were wondering why a restaurant like this could have poison on the menu." The tourists 20 . One of them said: "No. Poisson is French for fish." | ||||
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