Here’s How Earthquakes Are Measured
地震是如何测量的?
What does “moment magnitude” mean, and how do scientists determine the strength of a rupture in the earth?
什么是“矩震级”？科学家如何确定地球断裂的强度？
Seismologists register the intensity of an earthquake in units known as moment magnitude, which measure how much energy was released when the rocks along a fault moved during the quake.
地震学家用称为“矩震级”的单位来记录地震的强度，这个单位衡量的是地震发生时沿断层移动的岩石所释放的能量。
The moment magnitude scale, as it is known, replaced one developed by an American seismologist, Charles Richter, that was used until the 1970s.
“矩震级”替代了美国地震学家查尔斯·里克特开发的、使用到20世纪70年代的旧测量标准。
The Richter scale was found to be inaccurate for very large earthquakes.
事实证明，里克特震级对于特别大的地震计量不够准确。
The moment magnitude scale can be hard for nonexperts to decipher.
对于非专业人士来说，矩震级可能难以理解。
It is logarithmic, meaning that each whole number of magnitude represents about a 32-fold increase in the amount of energy released during a rupture.
它是对数型的，这意味着震级每增加一个整数，地震断裂释放的能量大约增加32倍。
So, for instance, an earthquake with a magnitude of 2.0 is not twice as strong as a quake with a magnitude of 1.0.
因此，例如，震级为2.0的地震并不意味着比震级1.0的地震强两倍。
Instead, the amplitude of shaking would be 10 times as great, and it would release 32 times as much energy.
实际上，震动幅度会增加10倍，而释放的能量将是原来的32倍。
The strongest earthquake ever recorded, a 9.5-magnitude one that occurred in Chile in 1960, was 30,000 times more powerful than a 6.5-magnitude quake, which itself can be very destructive.
1960年在智利发生的9.5级地震是有记录以来最强的地震，其能量是6.5级地震的3万倍，而6.5级地震本身就足以造成巨大破坏。
Magnitude is far from a complete measure of a specific quake’s destructiveness, however.
然而，震级远不能完全衡量一场地震的破坏力。
Other geological factors, like the location and depth of the fault and the type of rocks and soil it occurs in, can affect the amount of shaking and destruction that an earthquake can cause.
其他地质因素，比如断层的位置和深度、发生地震的岩石和土壤类型，都会影响地震引起的震动和破坏程度。
Construction methods and building standards can also play a major role in the amount of damage and the number of casualties.
建筑方法和建筑标准也会在破坏程度和人员伤亡中起到重要作用。
The timing of the event and whether people are at home, at work or out and about are also factors.
地震发生的时间，以及人们是待在家里、工作场所还是外出，也都是影响因素。
Scientists calculate a quake’s moment magnitude by using data from a network of instruments, called seismometers, spread across the world.
科学家通过全球分布的地震仪网络收集数据，来计算地震的矩震级。
Those instruments record the waves of shaking from the quake’s point of origin moving through the earth.
这些地震仪记录了从地震震源开始向地球各处传播的震动波。
Worldwide, the frequency of earthquakes has remained largely unchanged over many decades of study.
经过数十年的研究发现，全球地震发生的频率基本保持不变。
On average, there are about 1,500 quakes of a magnitude of 5.0 or higher every year.
平均每年会发生约1500次震级5.0或更高的地震。
Of these, about 15 have a magnitude of 7.0 or higher.
其中，大约15次地震的震级达到7.0或更高。
People nearby might not feel a tremor of less than 4.0 magnitude.
震源周边的人们可能不会感觉到震级低于4.0的地震。
A 5.0 event might rattle nerves but do only light damage.
5.0级的地震可能会让人感到恐慌，但通常只会造成轻微破坏。
At 6.0, moderate damage can be expected, especially to older and less resilient structures.
6.0级的地震可能会造成中度破坏，特别是对老旧和不够稳固的建筑。
Strong quakes of 7.0 and up can do major damage over a wide area, and a quake of 8.0 or greater anywhere near a population center would probably cause catastrophic damage and loss of life.
震级达到7.0及以上的强烈地震会在大范围内造成重大破坏，若8.0级或更强的地震发生在人口密集地区附近，可能会导致灾难性的破坏和人员伤亡。
Theoretically, a quake of magnitude 10 is possible, but the fault would have to be about 8,000 miles long, or about one-third of Earth’s circumference.
理论上，震级达到10的地震是可能的，但断层必须有大约8000英里（12875公里）长，约占地球周长的三分之一。
