About Earthquake
地震的閱讀文章 
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The earthquake that killed more than 50,000 people in Iran was part of a normal pattern that included quakes in California, New aledonia, Panama, Mexico and Indonesia in the last two weeks, the US Geological Survey said on Friday.
"We are in the norm of earthquake activity," seismologist Jim Devine said at the US agency that monitors earthquakes.
"We would need several more large earthquakes before we start considering something unusual," he said.
Asked whether any of these quakes were related, Devine said, "The short answer is, no they're not. The long answer is, of course, the entire Earth is always in some state of energy release. There are periods when there is more energy release than other times."
The Earth is made up of almost a dozen plates that can collide and release energy, and it is this energy release that creates the earthquake, Devine said. But he stressed that a quake on one side of the Earth does not trigger one on the other side.
"Ninety-five percent of the time they appear to be quite random," Devine said.
"I haven't seen anything in this current pattern that would indicate that it's out of the ordinary," he said.
Seismologists do not understand why there are times when the Earth appears to be in a more active mode, which results in more earthquakes, Devine said.
Between 1890 and 1906, there were an unusually high number of large earthquakes, including temblors in California and Chile that were higher than 8 on the Richter scale.
By contrast, in the 1980s, "We were `energy deficient,'" Devine said.
"We can tell you where they're likely to occur, how large they are likely to be, how often they occur and how the ground will respond around it. But we cannot tell you just when it's going to hit," he said.
Seismologists did not predict the earthquake in the Iranian town of Bam, but knew that the whole country was in an active area.
On a relative scale, the 6.8-magnitude earthquake in Bam was a small one, approximately the same size as the California earthquake that killed two people on Dec. 22.
But Bam's buildings, many of which were made of mud and straw, were not as earthquake-resistant as the structures in California.
The largest earthquake in the series occurred southeast of the Loyalty Islands, New Caledonia, on Dec. 27, with a magnitude of 7.3.
Other earthquakes erupted in Indonesia on Friday (6.1 magnitude) and Mexico on Thursday (6.3 magnitude).
A Christmas Day earthquake with a magnitude of 6.1 struck in a remote region close to the border of Panama and Costa Rica, killing at least one person.
Key words:
seismologist n.地震學家 erupted v.爆發 collide v.碰撞
trigger v.引起 random a.任意的 temblors n.地震
deficient a.不足的 predict v.預報
magnitude n.震級 straw n. 稻草
資料提供: 英文領域