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擊了海地，震憾了罕見這樣地震的地區(qū)。不過，世界各地由同樣的力量引發(fā)的這種災(zāi)難性地震并不罕見。如此說來(lái)，是震動(dòng)了沿加利福尼亞圣安德烈亞斯斷層帶城市的相同機(jī)制觸發(fā)了這次地震。

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級(jí)地震發(fā)生在任何地方都是具強(qiáng)大潛在破壞性的地震，但是，對(duì)海地來(lái)說這是異常嚴(yán)重的事件，可能具有更大的破壞性影響，因?yàn)檫@個(gè)貧困國(guó)家的基礎(chǔ)設(shè)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.
盡管因?yàn)橥ㄓ嵕€路中斷，來(lái)自當(dāng)?shù)氐牡卣鹩绊憟?bào)告各不相同，但是地質(zhì)學(xué)家能夠運(yùn)用全球通用的評(píng)價(jià)地震影響的方法，以及他們的地震原理知識(shí)拼湊出海地地震事件的面貌。

Sliding plates滑動(dòng)的板塊

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.
地震一般發(fā)生在犬牙交錯(cuò)的一塊塊地殼（板塊）間。這些板塊相向運(yùn)動(dòng)，大部分時(shí)間我們察覺不到它們的移動(dòng)。在這次海地的地震中，加勒比海和北美板塊東西相向滑動(dòng)。這種滑動(dòng)稱為走滑邊界（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.
壓力沿邊界各點(diǎn)以及地殼部分粘連的斷層增強(qiáng)；最終，壓力在強(qiáng)大的運(yùn)動(dòng)中突然釋放，導(dǎo)致斷層的兩面移動(dòng)，引發(fā)地震。因破裂而引發(fā)地震的斷層系，被稱為恩里基洛－芭蕉園斷層系（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.
世界的這部分地區(qū)很少見大地震，其部分原因是加勒比海板塊較小，其斷層系和圣安德烈亞斯不一樣長(zhǎng)，處在世界最大的板塊——太平洋和北美板塊之間的邊界上。

The unusually high magnitude of Tuesday’s quake for this region is part of the reason it has likely caused enormous damage to Haiti.
有可能對(duì)海地造成巨大破壞的部分原因，是該地區(qū)星期二發(fā)生的異乎尋常的高震級(jí)地震。

Intensity and infrastructure 基礎(chǔ)設(shè)施的強(qiáng)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.
地震能造成破壞的另一個(gè)因素是其強(qiáng)度。震級(jí)是測(cè)量地震釋放了多少能量的方法，而強(qiáng)度“只是人們感覺地震有多強(qiáng)的估計(jì)或測(cè)量。”美國(guó)地質(zhì)調(diào)查局的地震分析師唐·布萊克曼（Don Blakeman）說。

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.
影響地震強(qiáng)度的一個(gè)因素是人們感覺到地震影響的震中距離。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），“對(duì)地震而言，這是很淺的。”布萊克曼對(duì)LiveScience說。

"So everyone in Port-au-Prince is basically within 30 to 40 km [18 to 25 miles] of the earthquake," he added.
他補(bǔ)充說，“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）之內(nèi)。

"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.
美國(guó)地質(zhì)勘探局（USGS）和國(guó)家地震信息中心（NEIC）的凱瑞恩·貝德威爾（Carrieann Bedwell）說，“海地地震的深度非常淺，就是說，其釋放的能量離地面非常近。”

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.
布萊克曼解釋說，與此相反，南太平洋上的斐濟(jì)群島能夠經(jīng)歷來(lái)自地殼以下數(shù)百英里的地震，那已經(jīng)使他們距震中數(shù)百英里了。在南太平洋發(fā)生的地震深很多，是因?yàn)閮蓚€(gè)板塊不是相向交錯(cuò)滑動(dòng)，而是其中之一在另一板塊底下沉入地下很深處，使得地震在地表以下深得多的地方引發(fā)地震。這被稱為俯沖帶（subduction zone）。

Another unfortunate factor in the intensity equation for Haiti is the infrastructure involved.
對(duì)海地來(lái)說，強(qiáng)度公式中的另一個(gè)不幸因素是相關(guān)的基礎(chǔ)設(shè)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年在當(dāng)年世界大賽第三場(chǎng)比賽之前襲擊舊金山的洛馬普列塔地震（Loma Prieta earthquake）也是約7.0級(jí)地震。雖然地震奪走了許多人的生命，而且導(dǎo)致數(shù)十億美元的財(cái)產(chǎn)損失，但是，這座城市較高的建筑標(biāo)準(zhǔn)使其遭受的災(zāi)難比可能發(fā)生在海地的災(zāi)難低的多。

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.
據(jù)布萊克曼說，海地是個(gè)貧窮的國(guó)家，建筑標(biāo)準(zhǔn)松散，人口高度密集，其建筑更有可能倒塌。“不幸的是，那將是這里遭災(zāi)的很大因素。”他說。

Experts have estimated that the death toll will likely reach into the thousands, with untold numbers homeless.
專家估計(jì)，那里的死亡人數(shù)可能達(dá)到數(shù)千人，但沒有說流離失所的人數(shù)。

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.
另一個(gè)問題是，該地區(qū)相對(duì)罕見的大地震加上薄弱的公共通訊和教育，這可能意味著海地人沒有像加利福尼亞人那樣做好應(yīng)對(duì)這種災(zāi)難的準(zhǔn)備。

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.
來(lái)自震區(qū)的信息將有助于科學(xué)家通過提供從18和19世紀(jì)發(fā)生在當(dāng)?shù)氐乃^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區(qū)的未來(lái)地震威脅。

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.
地震的破壞到底有多嚴(yán)重仍有待觀察，可能幾天內(nèi)都不會(huì)完全清楚，因?yàn)閬?lái)自這個(gè)傷殘島國(guó)的報(bào)告逐步升級(jí)。聯(lián)合國(guó)和紅十字會(huì)都動(dòng)員了緊急行動(dòng)。

"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.
“毫無(wú)疑問，我們正面對(duì)著一場(chǎng)嚴(yán)重的人道主義突發(fā)事件，需要更多的救援努力。”聯(lián)合國(guó)秘書長(zhǎng)潘基文說。

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.
震后的問題中可能還有伴隨大震而來(lái)的無(wú)數(shù)余震。雖然余震一般比原震低幾級(jí)，仍然可能造成進(jìn)一步的破壞，特別是因?yàn)楹５亟ㄖ幱谖ｋU(xiǎn)的狀況。

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.
貝德威爾說。美國(guó)地質(zhì)勘探局已經(jīng)估計(jì)將有4.0級(jí)以上（包括5.9級(jí)和5.5級(jí)）余震40多次，還有許多震級(jí)更低的余震。預(yù)計(jì)今后幾天或幾周內(nèi)會(huì)發(fā)生更多余震，因?yàn)椴环€(wěn)定的斷層會(huì)繼續(xù)對(duì)將其移離原位的震蕩作出反應(yīng)。

"We like to think they are more repositioning of the faults in the area because of the larger earthquake," Bedwell said.
貝德威爾說，“我們這樣想，它們?cè)跒閿鄬釉谠摰貐^(qū)重新定位，因?yàn)檫@次地震更大。”