特别广播英语第 150 课：Predicting Earthquakes 预测地震-2

It is important to note that a reading of 4 indicates an earthquake ten times as strong as one with a reading of 3. 必须注意的是，读数为4级的地震表明其强度是读数为3级的10倍。

Scientists want to be able to predict those earthquakes that have a reading of over 4 on the Richter Scale. 科学家想预测那些读数超过里氏4级的地震。

How do earthquakes occur? Earthquakes are caused by the shifting of rocks along cracks, or faults, in the earth's crust. 地震是怎么发生的呢？地震是由地壳中的裂缝，或称断层处的岩石发生移位而引起的。

The fault is produced when rocks near each other are pulled in different directions. 当邻近岩石受到不同方向的拉力时便产生了断层。

The best-known fault in North America is the San Andreas fault in the state of California in the United States. 北美洲最著名的断层是位于美国加利福尼亚的圣安德烈亚斯断层。

The nations that are actively involved in earthquake prediction programs include Japan, China, Russia, and the United States. 积极参与地震预测计划的国家包括日本、中国、俄罗斯和美国。

These countries have set up seismic networks in areas of their countries where earthquakes are known to occur. 这些国家在已知发生地震的地区建立了地震网络，

These networks are on the alert for warning signs that show the weakening of rock layers that can precede an earthquake. 这些网络一直处于戒备状态，搜索着告警的迹象，这些迹象显示出在地震前可能发生的岩层松动的状况。

Many kinds of seismic instruments are used by the networks to monitor the movements of the earth's crust. 这些网络使用多种地震仪器来监测地壳的运动。