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爱尔兰地理学课程作业-解析地震学

论文作者:meisishow论文属性:短文 essay登出时间:2014-08-15编辑:meisishow点击率:5947

论文字数:1380论文编号:org201408141600595748语种:英语 English地区:爱尔兰价格:免费论文

关键词:冰川地震学科学家worldshock爱尔兰课程作业

摘要: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。

爱尔兰地理学课程作业


总体来说冰川地震学还是一个比较新的领域,是一门新兴的科学。直到20世纪50年代初,科学家才在加拿大巴芬岛报告“冰震”——冰层和饱和冻土的瞬间移动。随着兴趣的浓厚和设备的改进此领域有了长足的发展,而且现在科学家们已经熟悉了有意聆听全球冻土地区冰层的低吟和吱嘎。


这种被追踪的信号与我们日常所遇到的地震学并不相同;冰川的滑动与地壳的滑动起因不同,动态相异,并且如果有人执意聆听,发出的声音也有所差别。虽然大型地震能使远处构造活动区颤抖,但是地震与冰震被认为是不相干的活动。但是这周一篇发表于自然地球科学(Nature GeoScience)上的文章首次将两者联系起来。


THE title of glacial seismologist is, relatively speaking, a new one in science. It took until the early 1950s for scientists at Baffin Island in Canada to report “icequakes”, the sudden movement of ice and frozen, saturated earth. The field has grown considerably as both interest and instrumentation have progressed, and scientists are now accustomed to listening intently to the groaning and creaking of ice sheets in frozen regions around the globe.


But the pursuit has been considered inherently separate from seismology as we normally think of it; the slippage of ice sheets and that of slabs of the Earth’s crust arise from different causes, follow different dynamics and, for those who go to the trouble to listen, make different sounds. While a large earthquake can trigger tremors in distant, tectonically active regions, earthquakes and icequakes have been considered unconnected events. But this week saw the publication, in a paper in Nature Geoscience, of the first evidence linking the two.


Zhigang Peng, a seismologist at the Georgia Institute of Technology in America, and colleagues noticed that glacial calving—the falling of large chunks of ice from the end of a glacier into the sea—can be triggered by earthquakes that originate thousands of kilometres away. The tsunamis created by such quakes tug on icesheets, inciting ruptures and fractures.


But Dr Peng wondered whether remote earthquakes could trigger icequakes farther inland in Antarctica. To be sure, seismic activity is not uncommon in Antarctica; ice formation, too, triggers icequakes of smaller intensity. But the team was looking for something more substantial. They chose to examine data around the time of the 2010 earthquake in Chile—among the strongest on record, and not too distant from Antarctica. They suspected that only so-called surface waves, which travel along the Earth’s surface rather than through its bulk, could trigger icequakes. Such waves travel at a known speed and have characteristic frequencies, so the team knew what to look for and when.


On analysing the data from 42 Antarctic seismographs, they found 12 clear signals that marked the occurrence of icequakes within six hours of the Chilean quake, leaving little doubt as to the cause. Relatively speaking, the icequakes were minuscule. But as Kate Allstadt, an icequake specialist at the University of Washington, puts it, “things we think of as strong, like glaciers, can still react to them if the conditions are right'. Dr Allstadt has found that the annual load of snow on Washington’s Mt Ranier is enough to trigger thousands of icequakes each year.

Understanding these delicate mechanisms as they play out in Antarctica is critical because the vast majority of the planet's ice is trapped there. The movement and eventual loss of glaciers at the Earth’s poles will have a tremendous global impact; the collapse of the Western Antarctic Ice Sheet, which has arguably论文英语论文网提供整理,提供论文代写英语论文代写代写论文代写英语论文代写留学生论文代写英文论文留学生论文代写相关核心关键词搜索。

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