VOA标准英语2011--Earthquake Science Still a Shaky Busines

Earthquake Science Still a Shaky Business

The magnitude 5.8 earthquake that rattled 1 the East Coast of the United States in August caught everyone - even geologists 2 - by surprise. But even when there's reason to think an earthquake could be around the corner, scientists still can't make good predictions.

It’s been 200 years since big earthquakes rocked the New Madrid Seismic 3 Zone, a fault system that runs down the central U.S. through parts of Illinois, Missouri, Kentucky, Arkansas and Tennessee. The region has had plenty of smaller quakes since then, but no one can really say when the next big one might be.

The New Madrid earthquakes of the winter of 1811 to 1812 have become the stuff of legend. They were so powerful, the story goes, they made the Mississippi River run backwards 4.

“It was what we call a thrust fault," says Susan Hough of the U.S. Geological Survey in Pasadena, California. "And it came up to the surface beneath the river and actually created a stair step in the river bottom, to where it set up waves that went coursing back upstream.”

According to Hough, much of what we know about those early quakes comes from first-hand accounts, like this one written by future United States president Zachary Taylor, who felt the shaking 370 kilometers away in Louisville, Kentucky.

The sight was truly awful: houses cracking; chimneys falling; men, women and children running in every direction - in their shirts - for safety and a friend of mine was so much alarmed as to jump (out) of a window and was very much hurt.

Hough’s calculations put the largest New Madrid earthquake at about 7.0, the same magnitude as the January 2010 earthquake in Haiti. The official USGS estimate is 7.7.

The problem is, scientists can’t predict when, where, or even if another earthquake will happen.

Northwestern University geophysicist Seth Stein doesn’t expect another big quake at New Madrid anytime soon. He and others have been using GPS technology to measure how the ground moves - or deforms 6 - along active faults.

“Now, normally the way earthquakes work is that you store up energy, the ground deforms before a big earthquake - kind of like stretching a spring - and then it snaps, and you have an earthquake,” Stein says.

That warping 7 of the ground has been measured in California, Alaska, Oregon, and Washington - along every U.S. fault where we think a big earthquake is on the way. So that’s what Stein and his colleagues expected to see when they started taking those same kinds of GPS measurements at New Madrid.

To their complete surprise, they saw absolutely no motion of the ground. Stein says part of the explanation could be that seismic zones in the middle of a continent seem to behave differently from those in places like California, where the huge plates that make up the earth’s surface thrust up against each other.

“Faults in the middle of the continents will be active for short periods of time geologically, maybe a few thousand years, and then they’ll turn off and be inactive for times, and then start up again," he says. "So it looks like we may be seeing the end of one of those cycles.”

But many other geologists don’t agree. Robert Williams of the USGS in Colorado says you can’t ignore the past. The earthquakes 200 years ago liquefied the soil underground, blasting jets of wet sand out onto the surface.

“There’s been some great science done, with geologists digging into these 1811, 1812 sand blows, and then, lo and behold 8, discovering evidence for older sand blows caused by earthquakes of about the same magnitude as the 1811, 1812 sequence,” Williams says.

They realized that before 1811, there had been quakes in about 1450, and again before that, in 900. Williams says that pattern of very large earthquakes means another big one could be on the way.

“We can’t predict earthquakes. So the geologic 5 record is really the strongest piece of evidence we have to remain concerned about earthquakes there in the New Madrid region.”

Experts hope by the time the next big quake does hit the region, we’ll be ready for it.

点击收听单词发音  






1
rattled

  
 


慌乱的，恼火的


参考例句：





The truck jolted and rattled over the rough ground. 卡车嘎吱嘎吱地在凹凸不平的地面上颠簸而行。
Every time a bus went past, the windows rattled. 每逢公共汽车经过这里，窗户都格格作响。












2
geologists

  
 


地质学家，地质学者( geologist的名词复数 )


参考例句：





Geologists uncovered the hidden riches. 地质学家发现了地下的宝藏。
Geologists study the structure of the rocks. 地质学家研究岩石结构。












3
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。












4
backwards

  
 


adv.往回地，向原处，倒，相反，前后倒置地


参考例句：





He turned on the light and began to pace backwards and forwards.他打开电灯并开始走来走去。
All the girls fell over backwards to get the party ready.姑娘们迫不及待地为聚会做准备。












5
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。












6
deforms

  
 


使变形，使残废，丑化( deform的第三人称单数 )


参考例句：





Bad rheumatoid arthritis deforms limbs. 严重的类风湿性关节炎会造成四肢变形。
The specimen deforms under a tensile stress applied parallel to the fibres. 试样在平行于纤维的张应力作用下发生变形。












7
warping

  
 


n.翘面，扭曲，变形v.弄弯，变歪( warp的现在分词 )；使（行为等）不合情理，使乖戾，


参考例句：





Tilting, warping, and changes in elevation can seriously affect canals and shoreline facilities of various kinks. 倾斜、翘曲和高程变化可以严重地影响水渠和各种岸边设备。 来自辞典例句
A warping, bending, or cracking, as that by excessive force. 翘曲，弯曲，裂开：翘曲、弯曲或裂开，如过强的外力引起。 来自互联网












8
behold

  
 


v.看，注视，看到


参考例句：





The industry of these little ants is wonderful to behold.这些小蚂蚁辛勤劳动的样子看上去真令人惊叹。
The sunrise at the seaside was quite a sight to behold.海滨日出真是个奇景。