造成海地地震的原因

Haiti Earthquake Science: What Caused the DisasterBy Andrea Thompson, LiveScience Senior Writer

posted: 13 January 2010 12:46 pm ET
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The major earthquake that struck Haiti Tuesday may have shocked a region unaccustomed to such temblors, but the devastating quake was not unusual in that it was caused by the same forces that generate earthquakes the world over. In this case, the shaking was triggered by much the same mechanism that shakes cities along California's San Andreas fault.
星期二的大地震沉重地打击了海地，震憾了罕见这样地震的地区。不过，世界各地由同样的力量引发的这种灾难性地震并不罕见。如此说来，是震动了沿加利福尼亚圣安德烈亚斯断层带城市的相同机制触发了这次地震。

The 7.0-magnitude Haiti earthquake would be a strong, potentially destructive earthquake anywhere, but it is an unusually strong event for Haiti, with even more potential destructive impact because of the weak infrastructure of the impoverished nation.
海地的7.0级地震发生在任何地方都是具强大潜在破坏性的地震，但是，对海地来说这是异常严重的事件，可能具有更大的破坏性影响，因为这个贫困国家的基础设施非常薄弱。

While reports from the ground on the effects of the quake are spotty because of downed communication lines, geologists can use worldwide measurements of the event as well as their general knowledge of how earthquakes work to piece together a picture of what happened in Haiti.
尽管因为通讯线路中断，来自当地的地震影响报告各不相同，但是地质学家能够运用全球通用的评价地震影响的方法，以及他们的地震原理知识拼凑出海地地震事件的面貌。

Sliding plates滑动的板块

Earthquakes typically occur along the jigsaw-puzzle pieces of Earth's crust, called plates, which move relative to one another, most of the time at an imperceptibly slow pace. In the case of the Haiti quake, the Caribbean and North American plates slide past one another in an east-west direction. This is known as a strike-slip boundary.
地震一般发生在犬牙交错的一块块地壳（板块）间。这些板块相向运动，大部分时间我们察觉不到它们的移动。在这次海地的地震中，加勒比海和北美板块东西相向滑动。这种滑动称为走滑边界（strike-slip boundary）。

Stress builds up in points along the boundary and along its faults where parts of the crust stick; eventually that stress is released in a sudden, strong movement that causes the two sides of the fault to move and generate an earthquake. The fault system that ruptured to cause this quake is called the Enriquillo-Plantain Garden fault system.
压力沿边界各点以及地壳部分粘连的断层增强；最终，压力在强大的运动中突然释放，导致断层的两面移动，引发地震。因破裂而引发地震的断层系，被称为恩里基洛－芭蕉园断层系（Enriquillo-Plantain Garden fault system）。

Major earthquakes are rare in this part of the world in part because the Caribbean is a minor plate, with a fault system that isn't as long as, say, the San Andreas, which is at the boundary between two of the world's largest plates – the Pacific and North American plates.
世界的这部分地区很少见大地震，其部分原因是加勒比海板块较小，其断层系和圣安德烈亚斯不一样长，处在世界最大的板块——太平洋和北美板块之间的边界上。

The unusually high magnitude of Tuesday’s quake for this region is part of the reason it has likely caused enormous damage to Haiti.
有可能对海地造成巨大破坏的部分原因，是该地区星期二发生的异乎寻常的高震级地震。

Intensity and infrastructure 基础设施的强度

Another factor in the damage that a quake can cause is it intensity. While magnitude is a measurement of how much energy is released by an earthquake, intensity is "simply an estimate or a measure of how strongly that earthquake was felt," said Don Blakeman, an earthquake analyst with the United States Geological Survey.
地震能造成破坏的另一个因素是其强度。震级是测量地震释放了多少能量的方法，而强度“只是人们感觉地震有多强的估计或测量。”美国地质调查局的地震分析师唐·布莱克曼（Don Blakeman）说。

One factor that influences earthquake intensity is the distance to the epicenter of those who feel the earthquake's effects. In the case of the Haiti quake, the epicenter of the quake was only 10 miles (15 km) southwest of the capital Port-au-Prince and just 6.2 miles (10 km) below the Earth's surface, "which for earthquakes is very shallow," Blakeman told LiveScience.
影响地震强度的一个因素是人们感觉到地震影响的震中距离。海地地震的震中距首都太子港（Port-au-Prince）西南部只有10英里（15公里），在地表以下只有6.2英里（10公里），“对地震而言，这是很浅的。”布莱克曼对LiveScience说。

"So everyone in Port-au-Prince is basically within 30 to 40 km [18 to 25 miles] of the earthquake," he added.
他补充说，“因此，太子港的所有人距震中基本上都在30至40公里（18至25英里）之内。

"The depth of this earthquake in Haiti was very shallow meaning that the energy that was released is very close to the surface," said Carrieann Bedwell of the USGS and NEIC.
美国地质勘探局（USGS）和国家地震信息中心（NEIC）的凯瑞恩·贝德威尔（Carrieann Bedwell）说，“海地地震的深度非常浅，就是说，其释放的能量离地面非常近。”

In contrast, areas like the Fiji Islands in the South Pacific can experience earthquakes that originate hundreds of miles down in the Earth's crust, which would already put them hundreds of miles away from the earthquake, Blakeman explained. Earthquakes are much deeper in this the South Pacific because instead of two plates sliding past one another, one is descending deep into the Earth below the other, allowing earthquakes to originate much farther down below the surface. This is called a subduction zone.
布莱克曼解释说，与此相反，南太平洋上的斐济群岛能够经历来自地壳以下数百英里的地震，那已经使他们距震中数百英里了。在南太平洋发生的地震深很多，是因为两个板块不是相向交错滑动，而是其中之一在另一板块底下沉入地下很深处，使得地震在地表以下深得多的地方引发地震。这被称为俯冲带（subduction zone）。

Another unfortunate factor in the intensity equation for Haiti is the infrastructure involved.
对海地来说，强度公式中的另一个不幸因素是相关的基础设施。

The 1989 Loma Prieta earthquake that struck San Francisco just before Game 3 of the 1989 World Series was also about a 7.0-magnitude quake. While it killed scores of people and caused billions of dollars in property damage, the relatively high construction standards in the city kept the devastation much lower than what will likely be the case in Haiti.
1989年在当年世界大赛第三场比赛之前袭击旧金山的洛马普列塔地震（Loma Prieta earthquake）也是约7.0级地震。虽然地震夺走了许多人的生命，而且导致数十亿美元的财产损失，但是，这座城市较高的建筑标准使其遭受的灾难比可能发生在海地的灾难低的多。

Haiti is a poor country with lax building standards and high population density, which makes buildings more likely to crumble, according to Blakeman. "Unfortunately that's going to be a lot of the factor here," he said.
据布莱克曼说，海地是个贫穷的国家，建筑标准松散，人口高度密集，其建筑更有可能倒塌。“不幸的是，那将是这里遭灾的很大因素。”他说。

Experts have estimated that the death toll will likely reach into the thousands, with untold numbers homeless.
专家估计，那里的死亡人数可能达到数千人，但没有说流离失所的人数。

Another problem is the relative rareness of major earthquakes in the area coupled with poor public communication and education, which likely means that most Haitians were not prepared for such a disaster, as many Californians might be.
另一个问题是，该地区相对罕见的大地震加上薄弱的公共通讯和教育，这可能意味着海地人没有像加利福尼亚人那样做好应对这种灾难的准备。

Waiting for answers
等待回音

Information from the earthquake will help scientists better understand the future quake threat that exists for Haiti and the rest of the Caribbean by providing information that isn't available from the previously known major quakes in the region, which occurred in the 18th and 19th centuries.
来自震区的信息将有助于科学家通过提供从18和19世纪发生在当地的所谓大地震中得不到的信息，更好地了解存在于海地和加勒比海其它地区的未来地震威胁。

Just how bad the destruction from the quake will be remains to be seen and likely will not be known fully for days, as reports trickle in from the crippled island nation. The United Nation and Red Cross have both mobilized emergency efforts.
地震的破坏到底有多严重仍有待观察，可能几天内都不会完全清楚，因为来自这个伤残岛国的报告逐步升级。联合国和红十字会都动员了紧急行动。

"There is no doubt that we are facing a major humanitarian emergency and that a major relief effort will be required," said United Nations Secretary-General Ban Ki-moon.
“毫无疑问，我们正面对着一场严重的人道主义突发事件，需要更多的救援努力。”联合国秘书长潘基文说。

Compounding the problems of the quake aftermath will likely be the numerous aftershocks that accompany any major earthquake. Though aftershocks are typically several orders of magnitude below the original temblor, they can still cause further damage, especially with the precarious building situation in Haiti.
震后的问题中可能还有伴随大震而来的无数余震。虽然余震一般比原震低几级，仍然可能造成进一步的破坏，特别是因为海地建筑处于危险的状况。

The USGS has already measured more than 40 aftershocks above a 4.0 magnitude (including a 5.9 and 5.5 magnitude) and many more below that, Bedwell said. More aftershocks are anticipated in the coming days and weeks as the restive fault continues to react to the jolt that set it off in the first place.
贝德威尔说。美国地质勘探局已经估计将有4.0级以上（包括5.9级和5.5级）余震40多次，还有许多震级更低的余震。预计今后几天或几周内会发生更多余震，因为不稳定的断层会继续对将其移离原位的震荡作出反应。

"We like to think they are more repositioning of the faults in the area because of the larger earthquake," Bedwell said.
贝德威尔说，“我们这样想，它们在为断层在该地区重新定位，因为这次地震更大。”