地震预测新技术：暗光纤网络

When an earthquake hits or a volcano erupts, scientists traditionally record the shaking using a specially designed instrument called a seismometer. These sensors are extremely sensitive, but they’re also expensive and distributed unevenly around the world. So scientists are working on another strategy to monitor earthquakes: using fiber optic cables—like the ones that form the backbone of the internet.

当地震来临或火山爆发时，科学家通常会使用专门的地震仪器来记录震动。这些传感器是非常敏感的，但它们也是非常昂贵的，而且在世界各地分布不均衡。因此，科学家们正在制定另一个监测地震的策略：使用光纤电缆来预测地震。

“So the motions are very clear. Specifically, you can see the arrival of different bits of the seismic energy from the location at which the earthquake occurred. So the p wave and the s wave, and the different phases that move out from the site of rupture in the earth, are used by seismologists to locate the event. And so we can detect the important pieces of information above the noise using the fiber optic cable and then, in that way, the fiber optic measurement is just as good as a seismometer.”

“所以行动计划非常清楚。具体而言，你可以看到震源地震强度的不同点。所以p波和s波以及从地球破裂部位移出的不同阶段，这些被地震学家用来定位地震。所以我们可以使用光缆检测噪声之上的重要信息，这种光纤测量地震的方式和地震仪一样好。“

Nate Lindsey, a PhD student and seismologist at the University of California, Berkeley. Here’s how it works: the scientists basically take a snapshot of the fiber by shining a laser down it and measuring the photons that bounce back after scattering off of small cracks and impurities in the glass. By doing this tens of thousands of times a second, the researchers can record how the cable deforms as seismic waves pass through it.

加州大学伯克利分校的博士生和地震学家Nate Lindsey认为，以下是它的工作原理：科学家们基本上是通过激光照射光纤来测量，在玻璃中的小裂缝和杂质散射后反射回来的光子。 通过每秒数千次的研究，研究人员可以记录地震波如何通过电缆变形的。

So far, Lindsey’s team has tested the technique in optical fibers they installed themselves in Fairbanks, Alaska, and around the Bay Area. They got promising results. But their ultimate goal is to capitalize on the vast network of unused cables—known as dark fiber—that’s already been installed by telecommunications providers for future use. Dark fiber covers much of the country, and stretches across the ocean basins—which are hard to study using traditional seismometers.

到目前为止，Lindsey的团队已经测试了他们安装在费尔班克斯、阿拉斯加和湾区周围的光纤线路。他们得到了很好的结果 但是他们的最终目标是利用广泛的未使用电缆网络(被称为暗光纤) 已经被电信供应商安装，以备将来用来预测地震。深色纤维覆盖全国大部分地区，并且横跨海洋盆地地区，这些地区是很难用传统地震仪来研究的。

“To put the same sensor near a volcano that occurs offshore requires infrastructure to deploy the sensor, like a big boat. It also requires a tethered cable, a battery. The sensor has to be waterproof, obviously. It’s also very corrosive underneath the ocean, and so there’s been a limitation of our ability to study offshore volcanoes. Similarly faults. Earthquake processes are understood based on faults that are on land.”

“为了把同一个传感器放在离岸的火山附近地区，需要基础设施来部署传感器，就像一艘大船。它还需要系绳和电池。当然了传感器还必须防水。在海洋下面也有很强的腐蚀性，所以我们研究离岸火山的能力有限。地震的过程是根据地面上的故障来推理的。

“Offshore cables could also improve earthquake early warning systems in places like the Pacific Northwest, where big, dangerous earthquakes actually occur under the ocean.“We can record that earthquake more quickly and then provide a warning that much quicker. So it might be a second or two seconds more that this fiber optic technology provides.”

“海底电缆也可以改善太平洋西北地区的地震预警系统，这些地方在海底实际上发生了大规模的危险地震。”我们可以更快记录地震发生情况，然后提供更快的警报。所以这个光纤技术可能还要再过两秒钟才能实现。”

Lindsey is presenting his work this week at the fall meeting of the American Geophysical Union in New Orleans. The results were also published recently in Geophysical Research Letters. If the technique proves reliable, Lindsey says it could usher in a whole new way of studying earthquakes and volcanoes. All that dark fiber may shed light on the Earth beneath our feet.

Lindsey本周将在新奥尔良美国地球物理联盟秋季会议上介绍他的工作。该研究结果最近也发表在“地球物理研究快报上。Lindsey说，如果这项技术证明可靠，它可以引入一种研究地震和火山的全新方式。所有那些黑暗的纤维可能会在我们的地球上散发出更多光芒来。