章节大纲

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  • 地震

    The Mission District in San Francisco post-1906 earthquake, with buildings on fire and destruction visible.
     

    What causes the greatest damage in an earthquake?
    ::在地震中造成最大破坏的是什么?

    This photo shows the Mission District of San Francisco burning after the 1906  .  In this earthquake, the shaking broke the gas mains and the  water  pipes. When the gas caught fire, there was no way to put it out. The greatest damage in earthquakes is usually not from the ground shaking. The greatest damage is caused by the effects of that shaking, including fires, floods, and structural collapse.
    ::这张照片显示了1906年地震后旧金山任务区燃烧的情况。在这次地震中,震动打破了气管和水管。当气管着火时,没有办法熄灭。地震中最大的破坏通常不是来自地面的震动。最大的破坏是由震动的影响造成的,包括火灾、洪水和结构崩溃。

    Earthquake!
    ::地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震 地震

    An  earthquake  is sudden ground movement. This movement is caused by the sudden release of the  energy  stored in  . An earthquake happens when so much  stress  builds up in the rocks that the rocks break. An earthquake’s energy is transmitted by  .
    ::地震是突如其来的地面运动。 这一运动是由储存在其中的能源突然释放造成的。 当岩石破裂的岩石中出现如此巨大的压力时,地震就会发生。 地震的能量是由地震传播而来的。

    Causes of Earthquakes
    ::地震原因

    Almost all earthquakes occur at  plate boundaries . All types of plate boundaries have earthquakes.  Convection  within the Earth causes the  plates  to move. As the plates move, stresses build. When the stresses build too much, the rocks break. The break releases the energy that was stored in the rocks. The sudden release of energy is an earthquake. During an earthquake the rocks usually move several centimeters. Rarely, they may move as much as a few meters.  Elastic rebound theory  describes how earthquakes occur ( Figure   ).
    ::几乎所有地震都发生在板块边界。 所有类型的板块边界都有地震。 地球内部的对流导致板块移动。 随着板块移动, 压力会形成。 当压力过大时, 岩石就会破裂。 断裂释放了岩石中储存的能量。 能量的突然释放是一场地震。 在地震中, 岩石通常移动几厘米。 罕见的是, 它们可能会移动多达几米。 电磁反弹理论描述了地震是如何发生的( 图示 ) 。

    Elastic rebound theory showing fault movement during an earthquake.
     
    Elastic rebound theory. Stresses build on both sides of a fault. The rocks deform plastically as seen in Time 2. When the stresses become too great, the rocks return to their original shape. To do this, the rocks move, as seen in Time 3. This movement releases energy, creating an earthquake.

    Focus and Epicenter
    ::焦点和中心

    The two important words used to describe an earthquake's   are  focus  and  epicenter .
    ::用来描述地震的两个重要词是焦点和震中。

    Focus
    ::焦点

    The point where the rock ruptures is the earthquake’s  focus . The focus is below the Earth’s surface. A shallow earthquake has a focus less than 70 kilometers (45 miles). An intermediate-focus earthquake has a focus between 70 and 300 kilometers (45 to 200 miles). A deep-focus earthquake is greater than 300 kilometers (200 miles). About 75% of earthquakes have a focus in the top 10 to 15 kilometers (6 to 9 miles) of the  crust . Shallow earthquakes cause the most damage. This is because the focus is near the Earth's surface, where people live.
    ::岩石破裂是地震焦点的点。 焦点在地球表面之下。 浅度地震的焦点不到70公里(45英里 ) 。 中度地震的焦点在70至300公里(45至200英里 ) 之间。 深度地震的焦点在300公里(200英里 ) 以上。 大约75%的地震的焦点在地壳的顶部10至15公里(6至9英里 ) 。 浅度地震造成的破坏最大。 这是因为焦点在地球表面附近,人们居住的地方。

    Epicenter
    ::极地

    The area just above the focus, on the land surface, is the earthquake’s  epicenter  ( Figure   ). The towns or cities near the epicenter will be strongly affected by the earthquake.
    ::位于地表的上述地区是地震的震中(图 ) 。 震中附近的城镇将受到地震的严重影响。

    The relationship between an earthquake's focus and epicenter.
     
    The focus of an earthquake is where the ground breaks. The epicenter is the point at the surface just above the focus.

     

    Summary
    ::摘要

    • A sudden release of energy stored in rocks causes an earthquake.
      ::岩石中储存的能量突然释放 导致地震
    • The focus is where the rocks rupture. The epicenter is the point on the ground directly above the focus.
      ::焦点是岩石破裂的地方。中心是地面上直接在焦点上方的点。
    • Most earthquakes are shallow. Shallow earthquakes do the most damage.
      ::大多数地震是浅的,浅浅的地震造成的破坏最大。

    Review
    ::回顾

    1. Describe elastic rebound theory.
      ::描述弹性反弹理论。
    1. Where is an earthquake's focus? Where is its epicenter?
      ::地震的焦点在哪里?地震的中心在哪里?
    1. Why do shallow earthquakes cause the most damage?
      ::为什么浅水地震造成的破坏最大?

    Explore More
    ::探索更多

     

     

    1. What is it called when you feel the ground move?
      ::当你感觉到地面移动时,它叫什么来着?
    1. What does the Earth’s interior resemble? What is the outside layer called?
      ::地球的内部像什么?外层叫什么?
    1. What is Earth’s outer layer made of? What are they called?
      ::地球外层是由什么构成的?它们叫什么来着?
    1. How fast does this outer layer move usually?
      ::这个外层移动的速度通常有多快?
    1. What is a fault? How big are they?
      ::什么是错,它们有多大?
    1. What happens when too much pressure builds up at a fault?
      ::当压力过大导致错时会怎样呢?