|
海底光缆，能用来测量地震
图片来源：Pixabay 隐藏在海洋深处的，除了巨型甲壳类动物和令人毛骨悚然的鮟鱇，还有一条重要的科技线：将几乎所有大陆和群岛都与互联网相连的海底光缆。不过，除了让猫猫梗图向全球扩散外，这些深海光缆似乎还有其他用途。 “从海底光缆之中，我们能够很好地收集到地震信息。” 乔纳森·阿霍-富兰克林（Jonathan Ajo-Franklin）是美国莱斯大学（Rice University）和劳伦斯·伯克利国家实验室（Lawrence Berkeley National Lab）的应用地球物理学家。他说，光纤电缆就像内部混有杂质的玻璃细丝。当你把激光射入光纤时，这些杂质会让一部分激光反向散射回激光源。 “我们测量了这些反向散射激光随时间的变化，从而获得每个位置上电缆拉伸的信息。” 在美国加利福尼亚州蒙特雷（Monterey, California）海岸附近，有一段处于维修期的电缆，暂时没有用于通信。阿霍-富兰克林的团队研究了这段电缆中的细微形变，结果感应到一些小型地震，还能准确定位到海底未测绘的断层、观测到水柱（water column）的流动。所有这些都可能引起海洋学家的兴趣。 他们的研究发表在《科学》（Science）期刊上。 阿霍-富兰克林指出，在全球海洋中部署的地震仪相当稀少，“这是一片巨大的空白……[查看全文] Internet Cables Could Also Measure Quakes In addition to giant crustaceans and creepy anglerfish, the deep oceans hide a vital piece of technology: the cables connecting almost every continent and archipelago to the Internet. But it seems those undersea cables can be used for more than just sending cat memes around the world. “We can do a good job picking up earthquakes in offshore cables.” Jonathan Ajo-Franklin is an applied geophysicist at Rice University and Lawrence Berkeley National Lab. He says that fiber-optic cables are like threads of glass—and there are impurities built in. So when you shoot lasers through the fibers, those impurities backscatter some of the light right back to the laser source. “We make measurements of the change in the backscattered light over time, which gives you information on the stretch of the cable at each location.' His team took advantage of a brief maintenance period when a particular cable, off the coast of Monterey, California, was not being used for communication. The researchers studied the slight deformations in the cable and were able to sense a small earthquake, pinpoint unmapped faults in the seafloor and observe movements in the water column—all of which might be of interest to oceanographers. Their work is in the journal Science. [Nathaniel J. Lindsey, T. Craig Dawe and Jonathan B. Ajo-Franklin, Illuminating seafloor faults and ocean dynamics with dark fiber distributed acoustic sensing] Ajo-Franklin points out that seismometers are pretty sparse in the world’s oceans: “It’s a big blank spot…[full transcript] “ Lindsey, N.J., Dawe, T.C. and Ajo-Franklin, J.B., 2019. Illuminating seafloor faults and ocean dynamics with dark fiber distributed acoustic sensing. Science, 366(6469), pp.1103-1107. |
|
|
