◎黃裕美輯譯

Kenneth Hudnut sees trouble out his window. He works in Pasadena, Calif., in a sunny valley of palm trees, historic bungalows, gourmet coffee shops and elite institutions of higher learning and space technology. But Hudnut, a geo-physicist with the U.S. Geological Survey, knows that it also is home to something called the Sierra Madre fault, which is adjacent to something called the Cucamonga fault.

美國地質調查局地球物理學家赫德納特看著窗外，憂心忡忡，他在加州帕沙迪納工作，是個兩旁有棕櫚樹的陽光普照的河谷，歷史性的小平房，精選咖啡屋，和高等教育及太空科技的高等學術機構。但赫德納特心裡有數，這裡也是馬德雷山系斷層所在，這裡則緊鄰著所謂的庫卡莫格斷層。

That, in turn, is not far from the fabled San Andreas fault. What wor-ries Hudnut is the possibility of the geological equivalent of dominos: What if an earthquake on one fault causes a chain reaction

而這又距赫赫有名的聖安德里斯斷層不遠。赫德納特擔心的是地質學上發生骨牌效應的可能性：萬一某一斷層的地震引起連鎖反應？

That, he believes, is what happened in China last month in the earthquake that has so far been blamed for more than 69,000 deaths.

他相信，上個月發生在中國造成69,000人死亡的強震就是這麼發生的。

"The fault system that ruptured is a lot like the one right out my window here," Hudnut said.

赫德納特說：「破裂的斷層系統，很像我窗外這裡的那個斷層。」

Heightening his anxiety is the fact that many scientists were caught by surprise by the magnitude of the China earthquake, estimated at 7.9 by U.S. scientists. Sichuan province has a history of earthquakes, but none so devastating. It was not near the top of anyone's list of the most likely loca-tions for a great quake. The data from satellites, which can track the motion of vast plates of the Earth's crust, sug-gested a relatively moderate amount of strain building up in the rugged mountain front along the edge of the Sichuan basin.

使赫德納特更憂慮的事實是，很多科學家都被中國地震規模的強度嚇了一大跳，據美國科家偵測這次地震是芮氏規模7.9。四川省常發生地震，但從來沒有像這麼毀滅性的，也從來沒有任何人把它列為最可能發生超大強震的地點。衛星傳回的資料，可以追蹤地殼巨大板塊的運動，但資料顯示，沿四川盆地邊緣崎嶇高山面只累積了相對溫和的張力。

"The lesson that one gets from this Sichuan earthquake is that we don't yet fully understand where all the hazard is," said Eric Kirby, a Penn State geologist who has extensively studied faults in that part of China. "We knew this was an active moun-tain belt, but we didn't quite realize what it was capable of."

「我們從這次四川地震所得到的教訓是，我們還不完全清楚所有的危險到底潛伏在哪裡，」曾深入研究中國四川地區斷層的賓州州立大學地質學家柯比說。「我們知道這是個火山活躍地帶，但我們不太了解它有多大的能耐。」

Hudnut and his colleagues say they believe, based on preliminary data, that at least three different faults rup-tured in succession. Rarely has such a cascading event been documented. "Now that we see the cascading be-havior, we get even more nervous. We see the potential here in the Los Angeles area for an earthquake that's larger than what we thought it was capable of. We could get our come-uppance from Mother Nature any day here," he said.

赫德納特和他的同事表示，他們相信，根據初步資料，至少三個不同的繼層連續破裂，很少記錄到這種「級聯破裂」事件。「如今我們既然已經見證到這種級聯破裂的反應，我們更緊張了。我們可以看到在洛杉磯地區這裡，有可能發生比我們想像中更大的地震。任何一天大自然都可能讓我們得到報應，」他說。

James Dolan, a University of Southern California geologist, has put together a map that shows faults in the Los Angeles area butting up against one another like passengers on a sub-way at rush hour. "Some of these faults could link up in ways we had never anticipated, which could lead to larger events," Dolan said.

南加大地質學教授杜蘭拼湊了一個地圖，圖上顯示洛杉磯地區的斷層線，像交通尖鋒時段趕地鐵的乘客彼此衝撞。杜蘭說：「這些斷層有些彼此以我們未曾預料到的方式互相聯結，這就可能導致更大的震災，」杜蘭說。

"We don't really understand the Earth," said Thomas Jordan, director of the Southern California Earthquake Center. "There may be faults we don't even know about." For decades, the operating assumption in California has been that the Big One will be produced by the San Andreas fault, which marks the meeting point of two enormous tectonic plates: the North American plate and the Pacific plate. They're trying to slide past one another at a rate roughly the speed at which fingernails grow. But they spend most of their time locked tight. Strain builds. An earthquake is a fault's way of releasing that strain.

「我們並未真正了解地球，」南加州地震中心主任約丹說。「甚至可能還有些斷層是我們還不知道的。」數十年來，對加州的專業認知是，超巨大地震會由聖安德里斯斷層引起，因為這個斷層是北美洲板塊和太平洋板塊這兩大板塊交會點。他們以大約指甲成長的速率試圖滑過對方，但多半時候，他們緊緊卡住，張力不斷累積，發生地震，斷層才能釋出這些蓄積張力。

The San Andreas broke near San Francisco in 1906 -- triggering fires that destroyed much of the city -- and north of Los Angeles in 1857. But the southernmost part of the fault, east of Los Angeles and leading down to the Salton Sea, has not broken since the 17th century. That southern sec-tion is widely viewed as ripe for a major rupture.

聖安德里斯斷層1906年在舊金山附近破裂，引起火災並摧毀大半個城市；1857年則發生在洛杉磯以北，但斷層最南段，也就是洛杉磯以東，往南直到索爾頓海，自17世紀以來一直未曾斷裂。因此南段普遍認為，發生大破裂的時機已經成熟。

It will give first responders, school officials and government officials the opportunity to see how they would handle a magnitude 7.8 earthquake on the San Andreas. A recent study fore-cast 2,000 deaths and $200 billion in damage in such a disaster. Scientists have created a new model showing the earthquake hazards over time in any given part of California. The odds of a 7.5-plus earthquake somewhere in the state over the next 30 years are listed at 46 percent.

這將可以給初體驗者、學校和政府官員一個機會，看看他們如何因應聖安德里斯斷層規模7.8的強震。最近一項研究預測，這種災難會造成2,000人死亡，2千億財物損失。科學家已經製造一個新的模型，顯示在加州任何地方未來發生地震的可能性。機率是未來30年在加州某個地方發生規模7.5的強震的機率是46%。（取材自華盛頓郵報）

【詞解】

U.S. Geological Survey 美國地質調查局
geophysicist 地球物理學家
Sierra Madre fault 馬德雷山系斷層
Cucamonga fault 庫卡莫格斷層
San Andreas Fault聖安德里斯斷層
geological 地質學上的
dominos 骨牌效應
chain reaction 連鎖反應
caught by surprise 嚇了一大跳
magnitude 規模強度