未分类题

Can earthquake be predicted? Scientists are (1)_____ programs to predict where and when an earthquake will occur. They hope to (2)_____ an early warning system that can be used to (3)_____ earth-quakes so that lives can be saved. The scientists who are (4)_____ this work is called seismologists. The word seismologist is (5)_____ from the Greek word seismos, meaning earthquake.
Earthquakes are the most dangerous and (6)_____ of all natural events. They occur in many parts of the world. Giant earthquakes have been (7)_____ in Iran, China, India, Alaska, and so on. Two of the biggest earthquakes that were ever recorded (8)_____ in China and Alaska, which measured about 8.5 on the Richter Scale. The Richter Scale was (9)_____ by Charles Richter in 1935, and compares the energy (10)_____ of earthquakes. An earthquake that measures a 2 on the scale can be felt but causes (11)_____ damage. One that measures 4.5 on the scale can cause slight damage, and an earth-quake that has a reading of over 7 can cause (12)_____ damage. It is important to note that a reading of 4 indicates a quake ten times as strong as one with a reading of 3. How do earthquakes occur? Earthquakes are caused by the shifting of rocks along cracks, or faults, in the earth's crust. The (13)_____ is produced when rocks near each other are pulled (14)_____ different directions.
Earthquake (15)_____ is in its infancy. Scientists have only a (16)_____ understanding of the physical (17)_____ that cause earthquakes. Much more research has to be done. New and more up-to-date (18)_____ have to be found for collecting earthquake data and analyzing it. (19)_____, seismologists have had some success in predicting earthquakes. Several small earthquakes were predicted. While this is a small start, it is (20)_____ a beginning.