科学家担忧日本会发生更多大地震

Significant aftershocks continue to shake Japan, more than two months after the magnitude 9.0 earthquake that triggered massive tsunami, leaving 25,000 people dead or missing and creating a catastrophe at a coastal nuclear power plant.

在日本发生九级大地震两个多月后，较强的余震仍时有发生。那场大地震引发了海啸，造成2万5000人死亡或失踪，并导致一座沿海核电站发生核灾难。

Five tremors in excess of magnitude 5.0 on the Richter scale have shaken Japan just this week. But scientists are warning that the largest expected aftershock has yet to hit. And, new, devastating inland quakes can also be expected.

仅在这个星期就有五个震级在里氏五级以上的余震发生。然而，科学家警告说，最大的余震还尚未发生，而且日本内陆也有可能会发生新的地震。

Japan hopes to never again hear these chilling words. An NHK announcer describing the scene on March 11 as a huge tsunami washes away homes, fishing trawlers and vehicles in coastal communities.

But scientists are cautioning that a repeat for Japan - on a smaller scale - is not a matter of if, but when.

科学家警告说，日本还会再次发生地震，这不过是早晚的问题，只不过规模会相对小一些。

After analyzing the magnitude 9.0 quake, scientists in Japan and the United States are making that sobering conclusion.

日本和美国的科学家在对这场九级大地震进行分析后得出了这样令人感到警醒的结论。

Several studies indicate the descending Pacific Ocean plate and the overlying plate on which Japan sits, slipped past each other by up to 60 meters. The research indicates five portions of the fault - covering more than 600 kilometers - were ruptured in the quake. That forebodes more seismic activity.

一些研究指出，下沉的太平洋板块和日本所处的位于上方的板块相互交错达60米。研究显示，断层中有五个区域在地震中发生断裂，这些发生断裂的断层涵盖600多公里的地区。这也就预示会有更多地质活动发生。

And, because the March 11 quake seems to have transferred stress along the same fault, some scientists are cautioning about a magnitude 8.0 closer to the Tokyo metropolitan area, home to more than 30 million people.

同时，由于3-11大地震把同一断层的压力转移，一些科学家发出警告，一场8.0级的地震会在更靠近东京大都会的地区发生。东京大都会地区居住着3000多万人口。

However, others offer a wider geographical target, as far to the north as Hokkaido.

但也有一些专家划定了一个范围更大的区域，北侧甚至到达北海道。

A frequently cited time frame, by some of Japan’s most senior seismologists, is between now and the next ten months.

日本一些资历最深的地质学家估计，这场地震发生的时间范围将是现在到未来10个月之间。

However, professor Takeshi Sagiya at Nagoya University’s Research Center for Seismology, Volcanology and Disaster Mitigation is cautious about that narrow chronology.

不过，名古屋大学地震、火山和减灾研究中心的鹭谷威教授对这样的短期预测持谨慎态度。

"I'm not quite sure about the basis of those specific kind of prediction about aftershocks," said Sagiya. "Those aftershocks happening are quite variable from place to place, from time to time. It can happen with a month, or within days, from the main shock. But also it can happen within some decades."

他说：“我不是很肯定这些有关对余震发生的具体预测的理论依据。余震发生的时间和地点都有很大差异。余震可以在主震发生后的一个月或者几天之内发生。但也可能会在几十年之内发生。”

Geophysicist Seth Stein of Northwestern University in the U.S. state of Illinois says the forecast intensity is in line with historical data but, like professor Sagiya, he is more comfortable expressing an extended timeline.

美国西北大学的地球物理学家赛斯.斯坦说，对余震强度的预测和历史资料像吻合。与鹭谷威教授一样，斯坦也认为余震会在更长的时间范围内发生。"They are thinking of the possibility you could have a magnitude eight, which makes sense. The largest aftershocks of an earthquake over the years around the world we've observed tend to be about one magnitude unit less than the main shock, more likely within months, but it could be years."

“他们在考虑发生八级地震的可能性，这也是有道理的。我们所观测到的世界上地震发生后强度最大的余震通常要比主震小一级，一般是在几个月内发生，但也可能是在几年后。”

Professor Sagiya of Nagoya University says the March 11 quake also “activated” inland faults.

名古屋大学的鹭谷威教授说，3-11大地震还“激活”了内陆的断层。

"They may be not as large as magnitude eight, but because they occur just beneath our cities, our house, they can be quite disastrous," said Sagiya.

“它们可能不会有八级那么大，但是因为地震就在我们城市、房屋下面发生，这些地震将会是灾难性的。”

Professor Stein - a former editor of the Journal of Geophysical Research - agrees that as a result of the March 11 temblor - the fourth most powerful ever recorded - the quake risk has increased for Japan, one of the world’s most seismically active places.

西北大学的斯坦认为，鉴于3-11大地震是有记载以来的第四大地震，日本发生更多地震的危险增加。日本是世界上发生地震最频繁的国家。

"We sometimes use this analogy of a kid's game called 'booby trap' where you have a bunch of little blocks and there's a spring piston and it pushes on them. And, once you disturb one piece then you increase the possibility that the other pieces are going to be pushed and slip also," said Stein. "So if you think of Japan in that way you can realize that once you've had a huge earthquake of this sort there's a chance that a lot of faults could have smaller earthquakes."

他说，“我们有时候把地震和小孩子们玩的一种叫做‘陷阱’的游戏做比较。你有一些小砖块和一个活塞弹簧，弹簧挤着砖块。如果你推动一块砖，那么其它砖块被挤压和交错的机会也就增加了。因此如果你把日本想象成那样的话，你就会发现在这么大一场地震发生后，其它断层上发生很多较小地震的可能性就会存在。”

Seismologists caution the public that their work is still an inexact science. They note improvements for indicating where a big quake approximately will occur, but not when.

地震学家提醒公众，他们的研究仍然无法十分精确。他们表示，在预测大地震有可能发生的位置方面有了一些进步，但他们仍然不能预测地震发生的时间。

They also acknowledge that this year’s huge magnitude 9.0 was not anticipated, looking at the historical data.

地震学家还承认，通过研究历史数据他们并没有预期日本今年会发生这次大地震。

That was also the case with the December 2004 earthquake off western Indonesia, which measured magnitude 9.3.

同样，2004年12月印度尼西亚以西海域发生的9.3级大地震也没有被预测到。

That prompted seismologists and geologists to re-examine the world’s subduction zones, areas where oceanic plates slide beneath either a continental plate or another oceanic plate.

这就使地震学家和地质学家重新对世界隐没带进行研究。隐没带是指一个大洋板块沉入到一个大陆板块或另一个大洋板块而形成的聚合板块边缘区域。

Some of the researchers, analyzing fresh data, are now challenging the conventional thinking and willing to state that most, if not all, of the world’s subduction zones (more than a dozen are recognized) are able to generate quakes equal to or exceeding magnitude 9.0.

一些学者通过对新数据的分析后对传统理论提出挑战。他们指出，世界上绝大多数隐没带都可以产生九级或九级以上的地震。