In 132 CE, Chinese polymath Zhang Heng presented the Han court with his latest invention. This large vase, he claimed, could tell them whenever an earthquake occurred in their kingdom– including the direction they should send aid. The court was somewhat skeptical, especially when the device triggered on a seemingly quiet afternoon. But when messengers came for help days later, their doubts turned to gratitude. Today, we no longer rely on pots to identify seismic events, but earthquakes still offer a unique challenge to those trying to track them. So why are earthquakes so hard to anticipate, and how could we get better at predicting them?
在公元 132 年, 中国的博学家张衡 向汉朝宫廷展示了 他的最新发明。 他声称,这个巨大的地动仪 能够感知到任何时候 发生在中国的地震—— 并且指明哪里需要救助。 朝廷有些怀疑, 特别是在一个看上去安静的下午, 这个装置被触发了。 但当几天后,信使 带来求援的消息时, 他们的疑虑变为了感谢。 今天,我们不再依靠地动仪 来辨别地震的发生, 但是捕获到地震的发生任然是 一件独具挑战的事情。 所以,为什么地震 如此难被预测呢? 并且,我们怎样才能 更好的预测地震呢?
To answer that, we need to understand some theories behind how earthquakes occur. Earth’s crust is made from several vast, jagged slabs of rock called tectonic plates, each riding on a hot, partially molten layer of Earth’s mantle. This causes the plates to spread very slowly, at anywhere from 1 to 20 centimeters per year. But these tiny movements are powerful enough to cause deep cracks in the interacting plates. And in unstable zones, the intensifying pressure may ultimately trigger an earthquake.
为了回答这些问题, 我们需要了解一些 地震背后的理论知识。 地球的地壳被许多巨大、 不规则地岩石构成, 这些岩石被叫做构造板块, 每一个板块浮在炙热、 熔化的地幔层上。 这也使得板块地运动非常缓慢, 每年移动 1 到 20 厘米。 但即使是很微小地运动, 也会释放巨大能量 造成相互作用地板块 间形成巨大裂缝。 并且,在不稳定地区域, 板块间不断增加地 压力会引发一次地震。
It’s hard enough to monitor these miniscule movements, but the factors that turn shifts into seismic events are far more varied. Different fault lines juxtapose different rocks– some of which are stronger–or weaker– under pressure. Diverse rocks also react differently to friction and high temperatures. Some partially melt, and can release lubricating fluids made of superheated minerals that reduce fault line friction. But some are left dry, prone to dangerous build-ups of pressure. And all these faults are subject to varying gravitational forces, as well as the currents of hot rocks moving throughout Earth’s mantle.
监控这个微小运动 是一件很难得事, 但是转变为地震的事件 因素更加多样化。 不同的断裂线将 不同的岩石分开 面对压力有的很坚硬, 有的很松软。 不同的岩石对摩擦与 高温有不同的反应。 一部分岩石被融化, 并释放由超热的矿物质 构成的润滑液, 这减少了断裂线之间的摩擦。 但是一些是干燥的, 容易形成危险的内在压力。 所有这些断层受到 不同重力作用, 以及流经地幔的热溶岩。
So which of these hidden variables should we be analyzing, and how do they fit into our growing prediction toolkit?
所以,哪些隐含的参数 需要我们去分析? 并且,如何使得它们适应 不断更新的预测工具?
Because some of these forces occur at largely constant rates, the behavior of the plates is somewhat cyclical. Today, many of our most reliable clues come from long-term forecasting, related to when and where earthquakes have previously occurred. At the scale of millennia, this allows us to make predictions about when highly active faults, like the San Andreas, are overdue for a massive earthquake.
由于其中的一部分力 有固定的发生机率, 板块的行为具有周期性。 今天,我们的许多可靠 线索来自长期预测, 与之前发生地震的 时间与地点有关。 几千年来, 这种方法使得我们能够 预测何时断层高度活跃, 就像圣安东列亚斯, 这种活跃是大地震的前兆。
But due to the many variables involved, this method can only predict very loose timeframes. To predict more imminent events, researchers have investigated the vibrations Earth elicits before a quake. Geologists have long used seismometers to track and map these tiny shifts in the earth’s crust. And today, most smartphones are also capable of recording primary seismic waves. With a network of phones around the globe, scientists could potentially crowdsource a rich, detailed warning system that alerts people to incoming quakes. Unfortunately, phones might not be able to provide the advance notice needed to enact safety protocols. But such detailed readings would still be useful for prediction tools like NASA’s Quakesim software, which can use a rigorous blend of geological data to identify regions at risk.
但是由于太多的参数被考虑, 这种方法只能预测出 很模糊的时间表。 为了预测更加准确的时间, 研究人员调查地震前 地球产生的振动。 地质学家长期使用地震仪, 来捕捉并绘制出地球 地壳中的微小变化。 今天,大多智能手机也能 记录主要的地震波。 使用遍布全球的手机网络, 科学家能够融合这些丰富信息, 并研制出警告人们地震即将 来临的详细预警系统。 不幸的是手机并不能提供 人们所需要的预告信息, 来制定安全的方案。 但是一些详细的数据仍然有用, 对于像美国宇航局的 Quakesim 软件一样的预测工具, 它可以使用严谨的地址数据组合 来识别有风险的区域。
However, recent studies indicate the most telling signs of a quake might be invisible to all these sensors. In 2011, just before an earthquake struck the east coast of Japan, nearby researchers recorded surprisingly high concentrations of the radioactive isotope pair: radon and thoron. As stress builds up in the crust right before an earthquake, microfractures allow these gases to escape to the surface. These scientists think that if we built a vast network of radon-thoron detectors in earthquake-prone areas, it could become a promising warning system– potentially predicting quakes a week in advance.
然而,最近的研究表明 所有这些传感器也可能 无法察觉到最明显的地震信号。 在 2011 年, 就在日本东海岸发生地震前, 附近的研究人员记录到 惊人的高浓度的 同位素对:氡和钍。 当地震前地壳内压力增加时, 这些气体通过微小裂痕溢出到地表。 一些科学家认为如果 我们在地震多发地区 建造一个巨大的氡钍探测器网络, 它将成为一个有前景的预警系统 可能提前一周预报地震。
Of course, none of these technologies would be as helpful as simply looking deep inside the earth itself. With a deeper view we might be able to track and predict large-scale geological changes in real time, possibly saving tens of thousands of lives a year. But for now, these technologies can help us prepare and respond quickly to areas in need– without waiting for directions from a vase.
当然, 所有这些技术都无法和 直接观察地球内部相比。 一个深入的观点,我们可能 可以实时记录和预测地质变化, 每年有可能会拯救数万条生命。 但是对于现在, 这些技术能够帮助我们快速 准备与响应有需要的地区 不用等待地动仪的指示。