『新东方在线托福阅读』为托福考生准备了ETS托福TPO/Official 75 Passage2阅读练习：In paragraph 3, the author presents the characteristics of S-waves by真题题目及答案解析，TPO/Official 75 Passage2阅读原文范文音频翻译

托福TPO/Official 75 Passage2阅读原文In paragraph 3, the author presents the characteristics of S-waves by题目答案及解析-新东方托福官方网校手机版

地震波——由地震产生的能量波——让科学家们可以确定地球内部各圈层的位置、厚度和特性。

Seismic waves—energy waves produced by earthquakes—permit scientists to determine the location, thickness, and properties of Earth's internal zones.

它们产生于岩石体突然受扰动时，例如岩石破裂或断层发生时。

They are generated when rock masses are suddenly disturbed, such as when they break or rupture.

振动从震动源向四周传播，以不同速度穿过地球地壳和内部不同化学成分及物理特性的区域。

Vibrations spread out in all directions from the source of the disturbance, traveling at different speeds through parts of Earth's crust and interior that differ in chemical composition and physical properties.

这些波的主要类别分为纵波、横波和表面波。

The principal categories of these waves are primary, secondary, and surface.

这三种类型的波均通过名为地震仪的仪器记录。

All three types of waves are recorded on an instrument called a seismograph.

纵波（或称P波）是三种波中传播速度最快的，因此地震后它们会最先到达地震台站。

Primary waves, or P-waves, are the speediest of the three kinds of waves and therefore the first to arrive at a seismograph station after there has been an earthquake.

它们以每秒4到5千米的速度穿过地壳上部，但在接近地壳底部时则以每秒6或7千米的速度传播。

They travel through the upper crust of Earth at speeds of 4 to 5 kilometers per second, but near the base of the crust they speed along at 6 or 7 kilometers per second.

在纵波中，能量脉冲以压缩和膨胀交替形式传递，方向与波传播方向平行。

In these primary waves, pulses of energy are transmitted as a succession of compressions and expansions that parallel the direction of propagation of the wave itself.

因此，在地震中运动的部分岩体会被推向相邻岩体并反弹。

Thus, a given segment of rock set in motion during an earthquake is driven into its neighbor and bounces back.

相邻岩体撞击下一个岩体并反弹，后续岩体持续此运动。

The neighbor strikes the next particle and rebounds, and subsequent particles continue the motion.

振动能量呈类似手风琴的推拉运动，可通过固体、液体和气体传递。

Vibrational energy is an accordion-like push-pull movement that can be transmitted through solids, liquids, and gases.

当然，P波的传播速度会因介质密度和弹性特性不同而变化。

Of course, the speed of P-wave transmission will differ in materials of different density and elastic properties.

横波（或称S波）的传播速度比P波慢每秒1到2千米。

Secondary waves, or S-waves, travel 1 to 2 kilometers per second slower than do P-waves.

与P波不同，横波中岩石的振动方向与能量传播方向呈垂直角度。

Unlike the movement of P-waves, rock vibration in secondary waves is at right angles to the direction of propagation of the energy.

这种波可通过将一根绳子拴在挂钩上并摇动另一端来演示。

This type of wave is easily demonstrated by tying a length of rope to a hook and then shaking the free end.

绳索中会形成一系列波浪并向挂钩方向移动，即传播方向。

A series of undulations will develop in the rope and move toward the hook—that is, in the direction of propagation.

然而，绳索上的任意物体都会沿与传播方向垂直的方向上下运动。

Any given particle along the rope, however, will move up and down in a direction perpendicular to the direction of propagation.

正是由于更复杂的运动方式，S波比P波传播更慢。

It is because of their more complex motion that S-waves travel more slowly than P-waves.

它们是地震台站接收到的第二组波动。

They are the second group of oscillations to arrive at a seismograph station.

与P波不同，横波无法穿透液体或气体。

Unlike P-waves, secondary waves will not pass through liquids or gases.

P波和S波有时也被统称为体波，因为它们能穿透地球深处的内部或地体。

Both P- and S-waves are sometimes also termed body waves because they are able to penetrate deep into the interior or body of our planet.

体波在弹性更大的岩石中传播更快，因此其速度随着向地球内部更有弹性区域下移而逐步增加，当体波开始向地表上升时，速度则逐渐减缓。

Body waves travel faster in rocks of greater elasticity, and their speeds therefore increase steadily as they move downward into more elastic zones of Earth’s interior and then decrease as they begin to make their ascent toward Earth’s surface.

体波进入不同弹性的岩石时速度的变化会导致波的路径发生弯曲或折射。

The change in velocity that occurs as body waves invade rocks of different elasticity results in a bending or refraction of the wave.

数量众多的小折射使体波在地球内部呈现弯曲路径传播。

The many small refractions cause the body waves to assume a curved travel path through Earth.

体波不仅会受折射影响，还可能部分反射回密度高的岩层表面，就像光线会从抛光表面上反射一样。

Not only are body waves subjected to refraction, but they may also be partially reflected off the surface of a dense rock layer in much the same way as light is reflected off a polished surface.

Many factors influence the behavior of body waves.

体波传播的岩石温度升高会导致速度降低，而周围压力的升高则会导致波速相应增加。

An increase in the temperature of rocks through which body waves are traveling will cause a decrease in velocity, whereas an increase in confining pressure will cause a corresponding increase in wave velocity.

在没有刚性的流体中，S波无法传播，而P波则显著减速。

In a fluid where no rigidity exists, S-waves cannot propagate and P-waves are markedly slowed.

表面波是沿地球外层地壳传播的大振幅波动。

Surface waves are large-motion waves that travel through the outer crust of Earth.

其运动模式类似于投入池塘中心的鹅卵石激起的水波。

Their pattern of movement resembles that of waves caused when a pebble is tossed into the center of a pond.

当P波或S波从地壳内部传播至地表时，表面波便由此波动形成。

They develop whenever P- or S-waves disturb the surface of Earth as they emerge from the interior.

表面波是地震台站接收到的最后一类波动。

Surface waves are the last to arrive at a seismograph station.

它们通常是地震对人口密集区造成破坏的主要原因。

They are usually the primary cause of the destruction that can result from earthquakes affecting densely populated areas.

这种破坏性源于面波的能量集中于地表的薄层区域，它们的能量不会像体波那样，在经过的广大岩层迅速分散。

This destruction results because surface waves are channeled through the thin outer region of Earth, and their energy is less rapidly scattered into the large volumes of rock traversed by body waves.

Paragraph 2 indicates that compared to P-waves traveling through Earth's upper crust, P-waves traveling near the base of Earth’s crust

According to paragraph 3, the main reason that S-waves travel more slowly than P-waves do is that S-waves

In paragraph 3, the author presents the characteristics of S-waves by

The word “invade” in the passage is closest in meaning to

Which of the following can be inferred about body waves from paragraph 4 ?

According to paragraph 5, body waves travel more slowly through a mass of rock if the rock is

According to paragraph 6, why do surface waves create much of the destruction caused by an earthquake?

According to paragraph 6, surface waves differ from body waves in which of the following ways?

Look at the four squares  that indicate where the following sentence could be added to the passage. Since the rupturing of rock masses occurs deep within Earth, it cannot be directly observed, but it produces observable effects.  Where would the sentence best fit? Click on a square  to add the sentence to the passage.

Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.

Seismic Waves Seismic waves—energy waves produced by earthquakes—permit scientists to determine the location, thickness, and properties of Earth's internal zones.They are generated when rock masses are suddenly disturbed, such as when they break or rupture. Vibrations spread out in all directions from the source of the disturbance, traveling at different speeds through parts of Earths crust and interior that differ in chemical composition and physical properties.The principal categories of these waves are primary, secondary, and surface. All three types of waves are recorded on an instrument called a seismograph. Primary waves, or P-waves, are the speediest of the three kinds of waves and therefore the first to arrive at a seismograph station after there has been an earthquake. They travel through the upper crust of Earth at speeds of 4 to 5 kilometers per second, but near the base of the crust they speed along at 6 or 7 kilometers per second. In these primary waves, pulses of energy are transmitted as a succession of compressions and expansions that parallel the direction of propagation of the wave itself. Thus, a given segment of rock set in motion during an earthquake is driven into its neighbor and bounces back. The neighbor strikes the next particle and rebounds, and subsequent particles continue the motion. Vibrational energy is an accordion-like push-pull movement that can be transmitted through solids, liquids, and gases. Of course, the speed of P-wave transmission will differ in materials of different density and elastic properties. Secondary waves, or S-waves, travel 1 to 2 kilometers per second slower than do P-waves. Unlike the movement of P-waves, rock vibration in secondary waves is at right angles to the direction of propagation of the energy. This type of wave is easily demonstrated by tying a length of rope to a hook and then shaking the free end. A series of undulations will develop in the rope and move toward the hook—that is, in the direction of propagation. Any given particle along the rope, however will move up and down in a direction perpendicular to the direction of propagation. It is because of their more complex motion that S-waves travel more slowly than P-waves. They are the second group of oscillations to arrive at a seismograph station. Unlike P-waves, secondary waves will not pass through liquids or gases. Both P- and S-waves are sometimes also termed body waves because they are able to penetrate deep into the interior or body of our planet. Body waves travel faster in rocks of greater elasticity, and their speeds therefore increase steadily as they move downward into more elastic zones of Earth’s interior and then decrease as they begin to make their ascent toward Earth’s surface. The change in velocity that occurs as body waves invade rocks of different elasticity results in a bending or refraction of the wave. The many small refractions cause the body waves to assume a curved travel path through Earth. Not only are body waves subjected to refraction, but they may also be partially reflected off the surface of a dense rock layer in much the same way as light is reflected off a polished surface. Many factors influence the behavior of body waves. An increase in the temperature of rocks through which body waves are traveling will cause a decrease in velocity, whereas an increase in confining pressure will cause a corresponding increase in wave velocity. In a fluid where no rigidity exists, S-waves cannot propagate and P-waves are markedly slowed. Surface waves are large-motion waves that travel through the outer crust of Earth. Their pattern of movement resembles that of waves caused when a pebble is tossed into the center of a pond. They develop whenever P- or S-waves disturb the surface of Earth as they emerge from the interior. Surface waves are the last to arrive at a seismograph station. They are usually the primary cause of the destruction that can result from earthquakes affecting densely populated areas. This destruction results because surface waves are channeled through the thin outer region of Earth, and their energy is less rapidly scattered into the large volumes of rock traversed by body waves.