Why are earthquakes so hard to predict? - Jean-Baptiste P. Koehl

翻译人员: Jasper Han 校对人员: Tianji (Homer) Li

In 132 CE,

在公元 132 年，

Chinese polymath Zhang Heng

中国的博学家张衡

presented the Han court with his latest invention.

向汉朝宫廷展示了 他的最新发明。

This large vase, he claimed,

他声称，这个巨大的地动仪

could tell them whenever an earthquake occurred in their kingdom–

能够感知到任何时候 发生在中国的地震——

including the direction they should send aid.

并且指明哪里需要救助。

The court was somewhat skeptical,

朝廷有些怀疑，

especially when the device triggered on a seemingly quiet afternoon.

特别是在一个看上去安静的下午， 这个装置被触发了。

But when messengers came for help days later,

但当几天后，信使 带来求援的消息时，

their doubts turned to gratitude.

他们的疑虑变为了感谢。

Today, we no longer rely on pots to identify seismic events,

今天，我们不再依靠地动仪 来辨别地震的发生，

but earthquakes still offer a unique challenge to those trying to track them.

但是捕获到地震的发生任然是 一件独具挑战的事情。

So why are earthquakes so hard to anticipate,

所以，为什么地震 如此难被预测呢？

and how could we get better at predicting them?

并且，我们怎样才能 更好的预测地震呢？

To answer that,

为了回答这些问题，

we need to understand some theories behind how earthquakes occur.

我们需要了解一些 地震背后的理论知识。

Earth’s crust is made from several vast, jagged slabs of rock

地球的地壳被许多巨大、 不规则地岩石构成，

called tectonic plates,

这些岩石被叫做构造板块，

each riding on a hot, partially molten layer of Earth’s mantle.

每一个板块浮在炙热、 熔化的地幔层上。

This causes the plates to spread very slowly,

这也使得板块地运动非常缓慢，

at anywhere from 1 to 20 centimeters per year.

每年移动 1 到 20 厘米。

But these tiny movements are powerful enough

但即使是很微小地运动， 也会释放巨大能量

to cause deep cracks in the interacting plates.

造成相互作用地板块 间形成巨大裂缝。

And in unstable zones,

并且，在不稳定地区域，

the intensifying pressure may ultimately trigger an earthquake.

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,

监控这个微小运动 是一件很难得事，

but the factors that turn shifts into seismic events are far more varied.

但是转变为地震的事件 因素更加多样化。

Different fault lines juxtapose different rocks–

不同的断裂线将 不同的岩石分开

some of which are stronger–or weaker– under pressure.

面对压力有的很坚硬， 有的很松软。

Diverse rocks also react differently to friction and high temperatures.

不同的岩石对摩擦与 高温有不同的反应。

Some partially melt, and can release lubricating fluids

一部分岩石被融化， 并释放由超热的矿物质

made of superheated minerals

构成的润滑液，

that reduce fault line friction.

这减少了断裂线之间的摩擦。

But some are left dry,

但是一些是干燥的，

prone to dangerous build-ups of pressure.

容易形成危险的内在压力。

And all these faults are subject to varying gravitational forces,

所有这些断层受到 不同重力作用，

as well as the currents of hot rocks moving throughout Earth’s mantle.

以及流经地幔的热溶岩。

So which of these hidden variables should we be analyzing,

所以，哪些隐含的参数 需要我们去分析？

and how do they fit into our growing prediction toolkit?

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,

由于其中的一部分力 有固定的发生机率，

the behavior of the plates is somewhat cyclical.

板块的行为具有周期性。

Today, many of our most reliable clues come from long-term forecasting,

今天，我们的许多可靠 线索来自长期预测，

related to when and where earthquakes have previously occurred.

与之前发生地震的 时间与地点有关。

At the scale of millennia,

几千年来，

this allows us to make predictions about when highly active faults,

这种方法使得我们能够 预测何时断层高度活跃，

like the San Andreas,

就像圣安东列亚斯，

are overdue for a massive earthquake.

这种活跃是大地震的前兆。

But due to the many variables involved,

但是由于太多的参数被考虑，

this method can only predict very loose timeframes.

这种方法只能预测出 很模糊的时间表。

To predict more imminent events,

为了预测更加准确的时间，

researchers have investigated the vibrations Earth elicits before a quake.

研究人员调查地震前 地球产生的振动。

Geologists have long used seismometers

地质学家长期使用地震仪，

to track and map these tiny shifts in the earth’s crust.

来捕捉并绘制出地球 地壳中的微小变化。

And today, most smartphones are also capable

今天，大多智能手机也能

of recording primary seismic waves.

记录主要的地震波。

With a network of phones around the globe,

使用遍布全球的手机网络，

scientists could potentially crowdsource a rich,

科学家能够融合这些丰富信息，

detailed warning system that alerts people to incoming quakes.

并研制出警告人们地震即将 来临的详细预警系统。

Unfortunately, phones might not be able to provide the advance notice needed

不幸的是手机并不能提供 人们所需要的预告信息，

to enact safety protocols.

来制定安全的方案。

But such detailed readings would still be useful

但是一些详细的数据仍然有用，

for prediction tools like NASA’s Quakesim software,

对于像美国宇航局的 Quakesim 软件一样的预测工具，

which can use a rigorous blend of geological data

它可以使用严谨的地址数据组合

to identify regions at risk.

来识别有风险的区域。

However, recent studies indicate

然而，最近的研究表明

the most telling signs of a quake might be invisible to all these sensors.

所有这些传感器也可能 无法察觉到最明显的地震信号。

In 2011,

在 2011 年，

just before an earthquake struck the east coast of Japan,

就在日本东海岸发生地震前，

nearby researchers recorded surprisingly high concentrations

附近的研究人员记录到 惊人的高浓度的

of the radioactive isotope pair: radon and thoron.

同位素对：氡和钍。

As stress builds up in the crust right before an earthquake,

当地震前地壳内压力增加时，

microfractures allow these gases to escape to the surface.

这些气体通过微小裂痕溢出到地表。

These scientists think that if we built a vast network of radon-thoron detectors

一些科学家认为如果 我们在地震多发地区

in earthquake-prone areas,

建造一个巨大的氡钍探测器网络，

it could become a promising warning system–

它将成为一个有前景的预警系统

potentially predicting quakes a week in advance.

可能提前一周预报地震。

Of course,

当然，

none of these technologies would be as helpful

所有这些技术都无法和

as simply looking deep inside the earth itself.

直接观察地球内部相比。

With a deeper view we might be able

一个深入的观点，我们可能

to track and predict large-scale geological changes in real time,

可以实时记录和预测地质变化，

possibly saving tens of thousands of lives a year.

每年有可能会拯救数万条生命。

But for now,

these technologies can help us prepare and respond quickly to areas in need–

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

without waiting for directions from a vase.

不用等待地动仪的指示。