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地震知识知多少(转载)  

2012-05-29 05:48:18|  分类: 知识天空 |  标签: |举报 |字号 订阅

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以下原文转载自译言 - 编辑荐读

译者 123hurray

Just How Big Was the Biggest Earthquake?
This week marks the anniversary of the largest earthquake recorded, a magnitude-9.5 along southern Chile's coast in 1960
By Andrew Mustain and OurAmazingPlanet | May 24, 2012 | 3地震知识知多少(转载) - 大卫 - 峰回路转
地震知识知多少(转载) - 大卫 - 峰回路转
Image: Unknown, Courtesy of NOAA
This week marks the anniversary of the largest earthquake ever recorded — a magnitude-9.5 earthquake that ripped along the coast of southern Chile on May 22, 1960.

  本周是有史以来最大的地震的纪念日,该地震在1960年3月22日肆虐了智利的南海岸,震级达到了9.5级。

The colossal quake and the powerful tsunami that followed killed more than 1,400 people and left 2 million homeless in Chile. And its devastation reached far beyond South America.

  巨大的震动和随之而来的大海啸造成智利超过1400人丧生,二百万人流离失所。地震造成的破坏波及了整个南美大陆。

The tsunami swept across the Pacific Ocean, wreaking havoc in Hawaii, the Philippines and Japan; a day after the earthquake, walls of water up to 18 feet (5.5 meters) high rushed ashore at Honshu, Japan's main island, destroying 1,600 homes and killing 138 people.

  海啸席卷了太平洋及夏威夷,菲律宾和日本;震后一天,高达18英尺(5.5米)的水墙冲击了日本的主岛——本州,摧毁了1600所房屋,造成138人死亡。

The colossal quake was what is known as a megathrust earthquake. These giant quakes, the most powerful quakes the planet is capable of unleashing, occur alongsubduction zones, where one tectonic plate dives beneath another. [The 10 Biggest Earthquakes in History]

  这次地震被称作“大逆冲型”地震(该类地震由地层断层的上部上移而引发,地震释放能量的速度相对比较缓慢,能量难以一次性全部释放,所需要的时间就会更长。比如汶川地震 就属于这一型——译者注),这些巨大的地震发生的原因是地球能量的释放使得一个版块滑动到另一个版块之下。

In this case, the quake was caused when a 620-mile-long (1,000 kilometers) stretch of the Nazca plate, an oceanic plate that forms a large swath of the Pacific Ocean floor, lurched deeper beneath the South American plate, producing the only 9.5-magnitude quake on record.

  在这种情况下,纳斯卡板块(南美洲西岸以外东太平洋中的一个大洋板块——译者注)产生了620英里(1000公里)长的拉伸,在太平洋底形成了一个巨大的裂缝,引发南美板块底层的震动,从而导致了有史以来唯一一次的9.5级地震。 地震知识知多少(转载) - 大卫 - 峰回路转

So just how big is a 9.5? An earthquake magnitude video, created with an animation from Nathan Becker, an oceanographer at the Pacific Tsunami Warning Center, offers a simple way to understand the vast differences between one magnitude and the next.

  那么,9.5级的地震究竟有多大呢?太平洋海啸预警中心的海洋学家Nathan Becker用动画制作的地震震级视频能让我们对两个相邻震级地震的差别有一个简单的了解。

Essentially, each successive magnitude is 33 times larger than the last. That means a magnitude-8.0 earthquake is 33 times stronger than a 7.0, and a magnitude-9.0 earthquake is 1,089 (33 x 33) times more powerful than a 7.0 — the energy ramps up fast.

  从根本上说,震级每高一级,强度就大了33倍。这意味着8级地震的强度比7级要强22被。而9级地震则比七级强1089(33*33)倍——能量的上升得很快。

Magnitude measures

震级的测量

Although figuring out an earthquake's power requires lots of complicated math and lots of data, magnitude boils down to three basic factors: area, distance and friction.

  虽然测量地震的能量需要大量复杂的数学方法和数据,但震级总的来说与三个因素有关:断层面积、地震波移动距离和断层摩擦力。

"It's about the physical properties of the fault," said Paul Earle, a seismologist with the U.S. Geological Survey.

  “这与断层的物理属性有关”,美国地质研究中心的地震学家Paul Earle说。

To get the magnitude, Earle told OurAmazingPlanet, you multiply the area of the fault that slipped — how much real estate moved — by the distance it moved and by the amount of friction on the fault.

  Earle告诉"神奇的地球"栏目组,我们可以将断层的位移的面积乘以地震波移动的距离,再除以断层的摩擦力来计算震级。

Fiddling with any of those factors will change the magnitude.

  改变这些因素中的任何一个都会影响震级

Power limits

能量的限制因素

Yet some earthquakes are, by the mechanism that causes them, able to unleash far more power than others. All the most powerful earthquakes on record are so-called subduction earthquakes — the sort that happen where tectonic plates overlap.

  一些地震由于产生机理的关系,会释放比其他类型地震更多的能量。所有有记录的大地正都是所谓的“隐没式地震”(subduction earthquake,又译海沟地震——译者注)。这种类型的地震在大陆板块发生重叠的时候发生。

And that's because they simply have more real estate at their disposal than earthquakes that happen in the middle of a continental plate, known as strike-slip earthquakes.

  这就是为什么此类地震比其他发生于板块中部的“走滑地震”有更大的影响范围。

These earthquakes happen along faults that are, essentially, vertical — the San Andreas Fault is perhaps the most famous such fault in the United States.

  这些地震发生于垂直的断层,如美国最出名的圣安德烈(San Andreas)断层。

The faults that produce strike-slip quakes plunge into the Earth's interior in a fairly straight line. That means they reach hotter, gooier geological territory — places where the rocks aren't rigid enough to make an earthquake — faster than the faults at subduction zones, which head into the Earth at an angle.

  产生走滑地震的断层以近乎直线快速下沉到地球内部。这意味着它们到达了更热,更粘的地质区域,这些区域的岩石的硬度不足以造成地震。而俯冲带断层则是慢慢地以一个角度下沉。

"If you go straight down, you get to the nonbrittle zone faster than if you go at an angle," Earle said. And that means strike-slip faults just don't have as much area as the angled faults at subdcution zones, and thus can't produce quakes with quite as much punch.

  “如果你走的是直线,那么将会更快地进入非易碎区,”Earle说。这意味着走滑断层的面积比带角度的俯冲断层小,因此它们无法产生猛烈的地震。

Yet strike-slip quakes can still cause catastrophic damage. And scientists are hard at work on designing systems that will provide a few seconds of warning when an earthquake hits, no matter what the mechanism that caused it.

  但走滑地震仍然能造成灾难性的破坏。 无论地震是由何种机理引发,目前科学家在设计能在地震来临前几秒钟预警的系统方面都步履维艰。

地震知识知多少(转载) - 大卫 - 峰回路转
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