Ice Quake!
美国研究人员发现，南极洲冰流滑动能产生巨大震波，威力与地震相仿。这是研究人员首次在南极洲发现“冰震”。华盛顿大学教授道格拉斯·威恩斯从2001年开始在南极洲周边地区设置多台地震仪。从当年到2003年，地震仪监测到多次震波信号。威恩斯说：“起初我们不知道震波来自哪里，但最终我们确定震源为冰流。”监测数据显示，这块冰流宽约100公里，厚约800米。每次移动时，冰流发出的震波波及整个南极洲，最远甚至在澳大利亚都能监测到。浙江大学地球科学系教授陈汉林进一步解释了“冰震”现象。陈教授指出，这种“冰震”，就相当于大型的物体敲击水面，从而产生震波，与地震类似，而且，根据各种测定数据，也可以核算出震级来，这与炸药爆炸等产生一定震级的破坏力道理是一样的。当然，这种冰流的规模要够大，滑动时能产生足够大的能量，从而对下面的冰层乃至遥远的陆地产生一定的冲击波。
Over a hundred quakes have happened in the last decade. But they didn't occur near fault lines（断层线）. What were they near? Find out on this Moment of Science.
We’re used to thinking of earthquakes as (1)tremors（震动，颤抖） that happen along fault lines when tectonic plates （（地球表面的）构造板块）shift. They’re dramatic（吸引人注目的） events: a good-sized（相当大的，大型的） earthquake can bring buildings and bridges (2)toppling down（推翻；倒塌）.
Those destructive energy bursts are high frequency（高频） ground vibrations（震动）, and that’s the range of vibrations seismologists（地震学家） most actively study. Just recently, though, a geophysicist（地球物理学者） at Harvard University named G?ran Ekstr?m studied low-frequency（低频的） vibrations instead, and discovered something interesting.
He found over a hundred quakes have happened in the last decade that aren’t along any fault line. What are they near instead? Ice.
A glacier（冰川） can be thought of as a very (3)slow-moving（动作缓慢的） stream. It’s made of solid ice, but over long periods of time it can flow gradually over the land, sometimes carving deep (4)trenches（沟，沟渠） and (5)bulldozing（推土） up rock and soil. Just because it takes centuries to rearrange(重新排列) things, though, doesn’t mean a glacier isn’t enormously powerful at any given moment.
By carefully measuring seismic(地震的) signals, Ekstr?m was able to spot numerous low-frequency quakes in Greenland that hadn’t been identified. He also found that they mostly occurred during July, August, and September. Those warmer months melt lots of glacial ice.
Ekstr?m suspects that liquid water is （6）pooling（淤积） underneath the glacial ice to the point where the thin （7）veneer（外表） of water at the base of the glacier allows the whole mass to slip（滑动） a little, the way your foot can skid（打滑） on a slick（光滑的） road.
The quakes he recorded, he believes, are the vibrations set up by all that ice–in one case, six cubic（立方的） miles of it–skidding as much as forty-two feet in under a minute. When that much ice scrapes（刮掉，擦掉）, the earth itself shakes.
Notes:
(1)tremors ['trem?z] n.震动；颤抖（tremor的复数）v.颤动（tremor的三单形式）
1.They got only blushes, ejaculations, tremors, and titters, in return for their importunity.
她们只是用脸红、惊叫、颤抖和傻笑来回答他们的要求。
2.Rescuers are continuing into a third day the hunt for survivors of the earthquake that hit Peru's central coast, as fresh tremors shake the area.
救援一直持续到了第三天，搜寻发生在秘鲁中部海岸的地震后的幸存者，这次地震又引起了这个地区的震动。
(2)topple down 推翻；倒塌
The wounded soldier toppled down time after time.
伤兵一次又一次地跌倒。
(3)slow-moving ['sl?u'mu:vi?] adj.滞销的；动作缓慢的
We looked like a bunch of awkward kids riding a slow-moving carousel.
我们看起来就像一群骑在旋转木马上的笨拙的孩子。
(4)trench [trent?] n.沟,沟渠；战壕；堑壕 vt. 掘沟 vi.挖战壕；侵害
1.The soldiers trenched an outpost.
士兵们用战壕防御前哨。
2.A long narrow trench or furrow dug in the ground, as for irrigation, drainage, or a boundary line.
沟渠，排水沟，''。'水道'。''在地面上狭长的沟渠或细沟，用于灌溉、排水或用作分界线。
(5)bulldoze ['buld?uz] vt. 强迫；恫吓；用推土机清除
1.The workers bulldozed the building site.
工人们用推土机把建筑工地推平。
2.His normal style when confronted with an obstacle was to bulldoze it into submission.
在前进的道路上碰到障碍时，他通常的做法是铲平障碍，继续前进。
(6)pooling n.联营，合并；池化 v.积水成池；淤积（pool的ing形式）
1.The road was deeply rutted and pooled with rain.
道路坎坷不平，到处是坑坑洼洼的雨水。
2.Object pooling is a good example.
对象池就是一个很好的例子。
(7)veneer [v?'ni?] n.外表；虚饰；饰面；胶合板的一层；薄木片 vt.胶合；虚饰；给…镶以饰片
1.Civilization is a thin veneer over a very ancient structure.
文明是建立在古老结构上的一层薄薄的外表。
2.Book-matched and quartered cherry veneer recessed panel in base.
预订匹配和驻扎樱桃饰面休会小组在基地。 |