VOA标准英语2010年-Scientists Explain Haiti Earthquake

"This was a very shallow earthquake, which means it would tend to be more destructive." — Stuart Sipkin, USGS

Tuesday's earthquake hit Haiti hard, with extensive damage and many casualties.

Compared to the well-known seismic¹ areas like the Pacific Rim², the Caribbean seems geologically quiet, but this area — where tectonic plates meet — has a long history of earthquakes, tsunamis⁵, and volcanoes.

In 1946, the Dominican Republic, just across the border from Haiti, experienced a magnitude eight earthquake, which triggered a tsunami⁴. Other major recorded earthquakes in the 17th, 18th, and 19th centuries may have been produced by movement of the same fault that caused Tuesday's disaster.

Earthquakes generally occur when the tectonic plates that make up the Earth's crust move suddenly. Eric Calais, a geophysicist, says that sudden movement can follow a buildup of stress as adjacent plates struggle to move past each other.

"If you have a fault that is being strained at a speed of 7 mm per year, which is the case here," says the Purdue University professor. "The last major event on that fault occurred 250 years ago, so if the fault snaps, it's going to snap by 1.7 meters, and that's about a magnitude 7 earthquake."

There are different kinds of faults. In this case, the damage was caused by movement of a "strike-slip fault."

"It's a horizontal motion of two pieces of the Earth's crust on either side of a vertical⁶ crack in the Earth," said Calais. "That is very similar to the San Andreas Fault in California, for example. That is the way that fault operates as well."

In other cases, the plates may move up and down, rather than from side to side. Either way, the release of energy can cause tremendous damage. How much damage depends on several factors.

"The main factor is the earthquake's size," said Stuart Sipkin, a seismologist at the U.S. Geological Survey. "But then there is also the earthquake depth. As you can imagine, the deeper the earthquake goes, the more of the energy is attenuated⁷ or spread out as it goes toward the surface. This was a very shallow earthquake, which means it would tend to be more destructive. And then there's the proximity⁸ to where people live."

And, in fact, people live very close to the geologic³ fault that caused this earthquake.

"The city of Port au Prince, the capital of Haiti, is essentially⁹ built on that fault," said Purdue's Eric Calais.

The center of the earthquake was a scant¹⁰ 10 kilometers beneath the surface, and just 15 kilometers from the capital.

Tuesday's quake has been followed by a series of aftershocks, which Stuart Sipkin of the U.S. Geological Survey says are pretty typical.

"The aftershocks will start off being fairly large and fairly frequent, and then sort of peter out as time goes on, although you will see aftershocks for weeks to months after the earthquake. They will be decreasing in size and frequency, but at this point they're still large enough to be of concern in hampering¹¹ the rescue efforts."

Many of the aftershocks have been measured at over magnitude 5 - enough to cause additional damage, including toppling structures weakened by the original earthquake. 

 

1 seismic   

a.地震的，地震强度的

参考例句：

• Earthquakes produce two types of seismic waves.地震产生两种地震波。
• The latest seismic activity was also felt in northern Kenya.肯尼亚北部也感觉到了最近的地震活动。

2 rim   

n.(圆物的)边，轮缘；边界

参考例句：

• The water was even with the rim of the basin.盆里的水与盆边平齐了。
• She looked at him over the rim of her glass.她的目光越过玻璃杯的边沿看着他。

3 geologic   

adj.地质的

参考例句：

• The Red Sea is a geologic continuation of the valley.红海就是一个峡谷在地质上的继续发展。
• Delineation of channels is the first step of geologic evaluation.勾划河道的轮廓是地质解译的第一步。

4 tsunami   

n.海啸

参考例句：

• Powerful quake sparks tsunami warning in Japan.大地震触发了日本的海啸预警。
• Coastlines all around the Indian Ocean inundated by a huge tsunami.大海啸把印度洋沿岸地区都淹没了。

5 tsunamis   

n.海啸( tsunami的名词复数 )

参考例句：

• Our oceans are alive with earthquakes, volcanoes, and more recently, tsunamis. 海中充满着地震、火山，包括最近发生的海啸。 来自常春藤生活英语杂志-2006年2月号
• Please tell me something more about tsunamis! 请您给我讲讲海啸吧！ 来自辞典例句

6 vertical   

adj.垂直的，顶点的，纵向的；n.垂直物，垂直的位置

参考例句：

• The northern side of the mountain is almost vertical.这座山的北坡几乎是垂直的。
• Vertical air motions are not measured by this system.垂直气流的运动不用这种系统来测量。

7 attenuated   

v.（使）变细( attenuate的过去式和过去分词 )；（使）变薄；（使）变小；减弱

参考例句：

• an attenuated form of the virus 毒性已衰减的病毒
• You're a seraphic suggestion of attenuated thought . 你的思想是轻灵得如同天使一般的。 来自辞典例句

8 proximity   

n.接近，邻近

参考例句：

• Marriages in proximity of blood are forbidden by the law.法律规定禁止近亲结婚。
• Their house is in close proximity to ours.他们的房子很接近我们的。

9 essentially   

adv.本质上，实质上，基本上

参考例句：

• Really great men are essentially modest.真正的伟人大都很谦虚。
• She is an essentially selfish person.她本质上是个自私自利的人。

10 scant   

adj.不充分的，不足的；v.减缩，限制，忽略

参考例句：

• Don't scant the butter when you make a cake.做糕饼时不要吝惜奶油。
• Many mothers pay scant attention to their own needs when their children are small.孩子们小的时候，许多母亲都忽视自己的需求。

11 hampering   

妨碍，束缚，限制( hamper的现在分词 )

参考例句：

• So fraud on cows and development aid is seriously hampering growth. 因此在牛问题上和发展补助上的诈骗严重阻碍了发展。
• Short-termism, carbon-trading, disputing the science-are hampering the implementation of direct economically-led objectives. 短效主义，出售二氧化碳，进行科学辩论，这些都不利于实现以经济为主导的直接目标。