Is it Possible to Prepare for an Earthquake?: Crash Course Geology #15 · CrashCourse
本集讲解地震应对措施，适合练习灾害应对、安全知识和实用表达。
1960 was the year of the Big One.
1960年是那个“重大事件”发生的年份。
For ten minutes, massive tremors rolled through Valdivia, Chile.
在长达十分钟的时间里，强烈的地震震动席卷了智利的瓦尔迪维亚地区。
Buildings toppled.
建筑物纷纷倒塌。
Electrical wires snapped.
电线突然断裂了。
By the time the shaking stopped, the coastline had drifted 30 feet to the west, and increased the country’s total size by about 1500 football fields.
当震动停止时，海岸线已经向西移动了 30 英尺，这使得该国家的总面积增加了大约 1500 个足球场的面积。
But that wasn’t all.
但这还不是全部。
The quake triggered tsunamis that struck Hawai’i and Japan.
这次地震引发了海啸，海啸袭击了夏威夷和日本。
All told, the event left thousands dead or houseless.
据统计，这场灾难导致数千人死亡或无家可归。
To this day, it’s the biggest earthquake ever picked up by seismographs.
直到今天，这仍然是地震仪记录到的最大规模地震。
What I want to know is: Are we ready for the next Big One?
我想知道的是：我们是否已经为下一次重大灾难做好了准备？
Hi, I’m Sage, and this is Crash Course Geology.
大家好，我是Sage，这是《地质学速成课程》（Crash Course Geology）。
[THEME MUSIC] In the twenty-first century, we’re no stranger to geological disasters.
【主题音乐】在二十一世纪，我们对地质灾害已经不再陌生。
Our feeds and our screens can sometimes feel like a continuous loop of devastation.
我们的信息来源（如社交媒体）以及各种屏幕（如手机、电脑屏幕等），有时会给人一种“灾难不断循环”的感觉。
Which can make us feel more than a little helpless.
这让我们感到无比无助。
But here at Crash Course, we believe that the more we know, the better prepared we are for the future.
但在“Crash Course”这个平台上，我们坚信：我们所掌握的知识越多，就越能为未来做好准备。
So, grab your emotional support rock, and let’s get into it.
那么，拿出你那能给你带来情感支持的人或物（比如你的朋友、家人，或者是一块象征情感支持的“石头”吧），让我们开始讨论吧。
Last time, we learned that earthquakes are measured by magnitude, or the amount of energy they release.
上次我们了解到，地震是通过震级来衡量的，震级表示地震释放的能量大小。
Unlike hurricanes, which are measured on a scale from 1 to 5 based on wind speed, the magnitude scale has no upper limit.
与飓风不同，飓风的强度是根据风速用1到5的等级来衡量的；而地震的震级等级则没有上限。
But magnitude can also be captured in negative numbers, for really small earthquakes.
不过，对于那些非常微小的地震来说，其震级也可以用负数来表示。
Which happen a lot.
这种情况经常发生。
The National Earthquake Information Center registers about 20,000 earthquakes globally each year, but very few of those can be felt at all.
美国国家地震信息中心每年记录全球约2万次地震，但其中只有极少数地震能够被人们察觉到（即人们能够感受到地震带来的震动）。
Only about 15 or so are magnitude 7.0— a major earthquake that causes serious damage.
只有大约15次地震的震级达到了7.0级；这种级别的地震会造成严重的破坏。
And just one per year clocks in at 8.0 or greater— the kind of earthquakes that can totally destroy communities.
每年只有1次地震的震级达到8.0级或以上；这类地震足以彻底摧毁整个社区。
The good news is, there are natural limits to how big earthquakes can get.
好消息是，地震的震级存在自然限制，不会无限增大。
That’s because magnitude is related to the area of the fault— or fracture in the earth’s crust— that breaks when the earthquake occurs.
这是因为地震的震级与地震发生时发生断裂的断层（即地壳中的裂缝）的面积有关。
The bigger the fault’s area, the bigger the quake.
断层区域的面积越大，地震的震级也就越高。
Take the infamous San Andreas Fault that runs through most of California.
以臭名昭著的圣安德烈亚斯断层为例——这条断层贯穿了加利福尼亚州的大部分地区。
It’s almost vertical, and while it’s nearly 1300 kilometers long, it’s only about 16 to 19 kilometers deep.
这条峡谷几乎呈垂直状；虽然它的长度接近1300公里，但深度仅有约16至19公里。
So its area isn’t actually that big— even if it seems pretty big from my apartment 15 miles off its center.
因此，它的实际面积并没有那么大；尽管从距离中心15英里的我的公寓里看，它看起来相当庞大。
Earthquakes larger than a magnitude of 8.3 are extremely unlikely at the San Andreas Fault.
在圣安德烈亚斯断层上，发生震级超过8.3级的地震的概率极低。
Compare that to the earthquake that struck Valdivia: it occurred on a fault that dips at a shallow angle.
将这种情况与袭击瓦尔迪维亚的地震进行比较：那次地震发生在一条倾斜角度较小的断层上。
And it broke a section that's at
然后它损坏了位于某处的那部分结构。
least 1,000 kilometers long and as much as 200 kilometers wide— a much bigger total area— resulting in a magnitude of 9.5.
该地震的震源区域至少长达1000公里，最宽处达200公里，因此总面积非常大；其震级为9.5级。
The most active, earthquake-prone faults sit at
最活跃、最容易发生地震的断层位于……
the edges of tectonic plates— those massive slabs of crust and bits of the upper mantle that surf atop the lower mantle.
构造板块的边缘——那些巨大的地壳板块以及上地幔的碎片，它们漂浮在下面的地幔之上。
We go into a lot more detail in an earlier episode.
我们在之前的某一集中已经详细讨论过这个问题。
But the important thing to know now is that different tectonic plate movements result in different types of faults.
但现在需要了解的重要一点是：不同的地壳板块运动会导致不同类型的断层。
The San Andreas is an example of a transform fault, which forms when two tectonic plates grind past each other.
圣安德烈亚斯断层就是一个典型的转换断层的例子——这种断层形成于两个构造板块相互摩擦、相互移动的过程中。
Because the plates move side to side but not up or down, earthquakes at transform faults are shallow.
由于地壳板块只是水平移动（即左右移动），而不会上下移动，因此发生在转换断层上的地震属于浅层地震。
That’s why they produce intense shaking on Earth’s surface, like the devastating 7.9-magnitude quake that struck San Francisco in 1906.
这就是为什么这些地震会在地球表面引发强烈的震动——比如1906年袭击旧金山的、震级高达7.9级的毁灭性地震。