《那些古怪又讓人憂心的問題》第144期:15級地震(1)

RICHTER 15

ing-bottom: 75%;">

15級地震

Q. What if a Richter magnitude 15 earthquake were to hit America at, let's say, New York City? What about a Richter 20? 25?

Q．如果美國紐約城受到一場里氏15級的地震襲擊會發生什麼？里氏20級，25級呢？

——Alec Farid

——亞歷克•法裏德

A. THE RICHTER SCALE, WHICH has technically been replaced by the “moment magnitude”1 scale, measures the energy released by an earthquake. It's an open-ended scale, but since we usually hear about earthquakes with ratings from 3 to 9, a lot of people probably think of 10 as the top and 1 as the bottom.

A．里氏震級在學術上現在已經被“矩震級”1所取代，它們都是用來衡量地震釋放出的能量的多少。里氏震級沒有上限，不過由於我們平時瞭解到的地震都在3～9級之間，因而許多人都認爲最高就是10級，最低是1級。

In fact, 10 isn't the top of the scale, but it might as well be. A magnitude 9 earthquake already measurably alters the rotation of the Earth; the two magnitude 9+ earthquakes this century both altered the length of the day by a tiny fraction of a second.

事實上10級並不是上限，但實際情況下10級很有可能是最高的震級了。一場里氏9級的地震已經顯著改變地球的自轉了，本世紀內兩場里氏9級以上的地震都使得一天的長度發生了很小的一些變化。

A magnitude 15 earthquake would involve the release of almost 1032 joules of energy, which is roughly the gravitational binding energy of the Earth. To put it another way, the Death Star caused a magnitude 15 earthquake on Alderaan.

一場里氏15級的地震釋放出來的能量有將近1032焦耳能量，約相當於地球的引力結合能。換言之，死星在奧德蘭星球上引起了一場里氏15級的地震2。

You could in theory have a more powerful earthquake on Earth, but in practice all it would mean is that the expanding cloud of debris would be hotter.

理論上來講，地球上可能發生威力更大的地震，但這也只是意味着膨脹的碎片雲的溫度更高一些而已。

The Sun, with its higher gravitational binding energy, could have a magnitude 20 quake (although it would certainly trigger some kind of a catastrophic nova). The most powerful quakes in the known universe, which occur in the material in a superheavy neutron star, are about this magnitude. This is about the energy release you would get if you packed the entire volume of the Earth with hydrogen bombs and detonated them all at once.

太陽的引力結合能比地球更高，可能會發生里氏20級的陽震（雖然這可能會引發毀滅性的新星爆發）。已知宇宙範圍內威力最大的震動發生在一顆質量極大的中子星上，震級就約爲20級。釋放出的能量相當於你在地球那麼大的體積內堆滿氫彈，然後在一瞬間引爆。

We spend a lot of time talking about things that are large and violent. But what about the bottom end of the scale? Is there such a thing as a magnitude 0 earthquake?

我們已經花了很長時間討論龐大而劇烈的東西，如果我們走另一個極端呢？有沒有震級爲0級的地震？