翻译 NW 多瑙河鱼子酱 不要转载喵
LOS ANGELES, California (CNN) -- 本周二，一场里氏5.4级的地震撼动了洛杉矶都市圈。地震致使当地居民惊慌失措，但并未造成严重损伤。
但是，此次地震可以说是对那些未曾经历过地震的南加州居民的一种警告。一场“大地震”可能即将到来。
“这只是一个‘样本’，一个小小的‘样本’”，加州理工大学地震学家凯特.哈顿如是说。
“这场地震介于‘微小’与‘温和’之间”，她说。这场地震有百分之五的几率是一场更高强度地震的先兆。经过24小时之后，几率将降低到百分之一。
“每场地震都会释放少许势能”，哈顿说。“这些势能通常是九牛一毛。换句话说，与为另一场大地震所蓄积和正在蓄积的势能总量相比，这次地震所释放的势能微不足道。那场更大的地震未来某天可能就会发生。”
大地震到底会在什么时候发生呢？
“从地质学家的观点来看，答案是‘很快’”，她说。“但是地质学家习惯于在上百万年的跨度上思考问题，所以我觉得这不会为民众提供任何有价值的信息。我们只能时刻做好准备，因为它随时都可能发生。”
美国地址调查局（USGS）将里氏5.4级地震划定为“温和”。这一强度会对建筑物和其他构造造成轻微损伤。今年到目前为止，今年在美国共发生39起介于里氏5.0和5.9级之间的“温和”地震，在全世界范围内则是790起。
The last moderate quake to strike California was a magnitude 5.4 in April in the northern part of the state. A magnitude 4.4 struck the greater Los Angeles area in August 2007.
There is a 99 percent chance of California experiencing a quake of magnitude 6.7 or larger within the next 30 years, according to the Uniform California Earthquake Rupture Forecast, sponsored by the U.S. Geological Survey, the California Geological Survey and the Southern California Earthquake Center and published in Science Daily in April.
"This earthquake reminds us to be prepared," said California Gov. Arnold Schwarzenegger. "We were very fortunate that there were no serious injuries or property damage."
He said he believes the state is "as prepared as anyone can be. We have continuous discussions about that. We are fanatics about emergencies and to be ready."
The largest earthquake in recent years in California was a magnitude 7.1 in 1999, Hutton said. But it was centered in the desert, near Twentynine Palms, in a sparsely populated area.
Tuesday's quake struck about 11:42 a.m., according to the USGS. Its epicenter was about 2 miles southwest of Chino Hills and about 5 miles southeast of Diamond Bar.
The epicenter was about 7.6 miles deep, making it a fairly shallow quake, according to CNN meteorologist Chad Meyers. In general, earthquakes centered closer to the surface produce stronger shaking and can cause more damage than those further underground. But most Southern California earthquakes tend to be fairly shallow, officials said.
More than 30 aftershocks were recorded. Hutton said the largest was a magnitude 3.6.
Los Angeles police said a downtown hotel sustained some structural damage, but no one was injured and the building was not evacuated. There were some unconfirmed reports of minor injuries. The White House was also monitoring the situation, said spokeswoman Dana Perino.
Despite the absence of serious damage or injuries, some Los Angeles-area residents were left rattled. The quake was felt as far south as San Diego, California, and the USGS said it received reports of light shaking as far north as Rosamond, California, about 55 miles north-northeast of Los Angeles.
Reports from those who felt the quake poured into CNN. Did you feel the quake?
"My house was like a fun house. Everything was moving," said Danny Casler, 28, of Huntington Beach. He said he was sleeping when his house began shaking, and some things fell in the living room. He said he ran out of the house in his boxer shorts.
Attorney Kevin Crisp said he was on the phone with his partner, who burst out, "Big quake!" Crisp said he felt it about five seconds later. "This was very impressive. Long and very uniform. Really had the building going." He said doors were swinging on the hinges and bottles of wine were rolling back and forth on his shelf.
"It just started with a really strong jolt," said Wendy Criner. "I ran and got my daughters from different rooms, and we squatted in the living room. I did have stuff fall off the shelf, some books in my daughters' room and some things in the kitchen."
The quake knocked out a ground radar system at Los Angeles International Airport, but that has not interfered with operations, according to the Federal Aviation Administration. Technicians were working to restore the system, which helps controllers monitor traffic on the ground. Also, tiles fell from the ceiling in one terminal as water flowed from a burst pipe.
The calculation of the quake's magnitude fluctuated as seismologists reviewed the data. Initially classified as a magnitude 5.8, the quake's intensity was reduced to a 5.6 and then to a 5.4. Because the earthquake magnitude scale is exponential, a 5.8 magnitude quake is four to five times more intense than a 5.4.
Two nuclear plants are in the vicinity of the quake's epicenter near Chino Hills, according to the Nuclear Regulatory Commission. The closest to the epicenter is in San Onofre, 50 miles south, but an NRC spokesman said, "this is well below the threshold for any conceivable damage to the plants."
"In the U.S. particularly in California, buildings are generally built well enough that it takes about a 5.5 for there to be some damage, so we do have the potential for damage," said Don Blakeman, an analyst for the USGS. "It depends on the structures [and] the ground the building is built on."
He said he would expect objects to be knocked from shelves and some windows broken. "It's kind of on the margin where you'll get some structural damage from these. We may find that some of the older homes and buildings that weren't retrofitted suffer more damage than the newer structures.
"I would expect some cracked buildings," he said. "There is the potential for injuries, but hopefully we won't have too much of that."
Blakeman's comments came before the quake's magnitude was dropped to a 5.4. However, he said afterward that the change does not affect his expectations, although obviously there is less potential for damage.
Still, the quake jolted the nerves of many Californians.
"I've lived in California, I've lived through several of them," Margot Wagner of Santa Barbara told CNN. "It's always a little unnerving." |
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发表于 2008-7-30 12:07:35
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湖人主场没啥问题吧？
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