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April 18, 1906, California's San Andreas Fault snaps, shaking San Francisco for nearly 60 terrifying seconds. When the trembling stops, the disaster is only beginning. Gas lines rupture, setting off massive fires, some 700 people die. Most of the city is reduced to ruins. This trembling of the ground caused when masses of rocks suddenly shift below the Earth's surface is called an earthquake. Hundreds of little earthquakes shake the planet every day, but most pass unnoticed. They usually occur along the boundaries of the thin plates that cover the Earth like an egg shell.
1906年4月18日，加州圣安德烈亚斯断层引发旧金山了近60秒钟的可怕地震。震感的消失只是灾难的开始。输气管道的破裂引发大火，导致近700人死亡。城市大部分只剩下灰烬。大量岩石突然移动到地表以下从而使地面震动的现象被称为地震。每天都会发生小型地震，只是大多数都不为人所注意。地震一般都在较薄的板块边缘沿线发生，而较薄的板块对地球而言就像鸡蛋壳一样。
Driven by the heat deep within the Earth's core, the plates grind against each other along lines called faults. When a plate's motion is blocked, stress builds up. Finally the fault gives way. The released energy raises through the Earth in the form of seismic waves. Scientists record these waves on a device called a seismograph. These zigzag lines show the strength of various seismic waves. Using the line, scientists grade the earthquakes on the Richter scale. For a quake to measure one number higher on the Richter scale, it must release about 30 times as much energy as the number below it.
在地球内核内部深处热量的驱动下，各个板块会在断层线上彼此摩擦。一旦某个板块的移动受阻，就会产生压力。最后断层线彼此错开。过程中释放出的能量会以地震波的形式出现。科学家用地震仪这个装置来记录地震波。这些Z字形线条可以表明各种地震波的强度。通过这些线条，科学家可以里克特来给不同的地震定级。里克特每上升一级，就意味着要多释放近30倍左右的能量。
Every year about 100,000 earthquakes rumble through the ground hard enough for people to feel them. Of these, only about 1,000 are strong enough to damage property. But a powerful earthquake can be devastating. On average, about 10,000 people die each year as a result of earthquakes. The greatest recorded earthquake ever to hit North America measured a massive 9.2. The tremor struck Alaska on March 28, 1964. A camera onboard a ship docked in Valdez recorded the draining of the entire harbor as a chasm opened up on the seafloor.
每年都有近10万场地震不为人所知。其中，只有近1000场地震震感强大，足以毁坏财物。但强震级的地震是具有毁灭性的。每年平均有近1万人在地震中死亡。有记录以来，北美洲遭受过的最强地震，其震级达9.2。那是1964年3月8日，阿拉斯加州发生的地震。停泊在瓦尔迪兹一艘船上的相机记录下了整个海港发生地震时的巨变，这是海底一道裂纹撕开所导致的天灾。
There is no stopping the surface of the Earth from changing and moving, so engineers are focusing on ways to create better buildings, highways and bridges, structures that will remain safe and stay in one piece the next time the Earth begins to shake.
地表是不会停止改变和移动的。所以很多工程师都在着重想办法建造更好的楼房、高速公路和桥梁，这样的结构才能始终保持安全，而且即便下一次发生地震也能保持完好无损。
1906年4月18日，加州圣安德烈亚斯断层引发旧金山了近60秒钟的可怕地震。震感的消失只是灾难的开始。输气管道的破裂引发大火，导致近700人死亡。城市大部分只剩下灰烬。大量岩石突然移动到地表以下从而使地面震动的现象被称为地震。每天都会发生小型地震，只是大多数都不为人所注意。地震一般都在较薄的板块边缘沿线发生，而较薄的板块对地球而言就像鸡蛋壳一样。
Driven by the heat deep within the Earth's core, the plates grind against each other along lines called faults. When a plate's motion is blocked, stress builds up. Finally the fault gives way. The released energy raises through the Earth in the form of seismic waves. Scientists record these waves on a device called a seismograph. These zigzag lines show the strength of various seismic waves. Using the line, scientists grade the earthquakes on the Richter scale. For a quake to measure one number higher on the Richter scale, it must release about 30 times as much energy as the number below it.
在地球内核内部深处热量的驱动下，各个板块会在断层线上彼此摩擦。一旦某个板块的移动受阻，就会产生压力。最后断层线彼此错开。过程中释放出的能量会以地震波的形式出现。科学家用地震仪这个装置来记录地震波。这些Z字形线条可以表明各种地震波的强度。通过这些线条，科学家可以里克特来给不同的地震定级。里克特每上升一级，就意味着要多释放近30倍左右的能量。
Every year about 100,000 earthquakes rumble through the ground hard enough for people to feel them. Of these, only about 1,000 are strong enough to damage property. But a powerful earthquake can be devastating. On average, about 10,000 people die each year as a result of earthquakes. The greatest recorded earthquake ever to hit North America measured a massive 9.2. The tremor struck Alaska on March 28, 1964. A camera onboard a ship docked in Valdez recorded the draining of the entire harbor as a chasm opened up on the seafloor.
每年都有近10万场地震不为人所知。其中，只有近1000场地震震感强大，足以毁坏财物。但强震级的地震是具有毁灭性的。每年平均有近1万人在地震中死亡。有记录以来，北美洲遭受过的最强地震，其震级达9.2。那是1964年3月8日，阿拉斯加州发生的地震。停泊在瓦尔迪兹一艘船上的相机记录下了整个海港发生地震时的巨变，这是海底一道裂纹撕开所导致的天灾。
There is no stopping the surface of the Earth from changing and moving, so engineers are focusing on ways to create better buildings, highways and bridges, structures that will remain safe and stay in one piece the next time the Earth begins to shake.
地表是不会停止改变和移动的。所以很多工程师都在着重想办法建造更好的楼房、高速公路和桥梁，这样的结构才能始终保持安全，而且即便下一次发生地震也能保持完好无损。
