专家：智利地震系百年不遇"超级地震"

The huge earthquake that struck off the coast of Chile belongs to an "elite class" of mega earthquakes, experts said, and is similar to the 2004 Indian Ocean temblor that triggered deadly tsunami waves.

The magnitude-8.8 quake was a type called a "megathrust," considered the most powerful earthquake on the planet. Megathrusts occur when one tectonic plate dives beneath another. Saturday's tremor unleashed about 50 gigatons of energy and broke about 340 miles of the fault zone, according to the US Geological Survey's National Earthquake Information Center.

The quake's epicenter was offshore and occurred about 140 miles north of the largest earthquake ever recorded — a magnitude-9.5 that killed about 1,600 people in Chile and scores of others in the Pacific in 1960.

"It's part of an elite class of giant earthquakes," said USGS geologist Brian Atwater.

If the magnitude holds, it will tie with the 1906 offshore Ecuador quake as the fifth largest since 1900.

"We call them great earthquakes. Everybody else calls them horrible," said USGS geophysicist Ken Hudnut. "There's only a few in this league."

The Chile quake was smaller than the Sumatra quake of 2004, a magnitude-9.1 and was not expected to be anything nearly as destructive. That quake and ensuing tsunami killed 230,000 people. Another difference is that the Chile quake triggered tsunami warnings hours ahead of time in Hawaii and Pacific islands, allowing people time to flee to higher ground.

In 2004, there was little measuring technology in place to warn Indian Ocean countries about incoming killer waves.

More than 100 aftershocks measuring magnitude-5 or larger rattled Chile throughout the day. So far, the quake death toll has surpassed 300 — a number that will likely rise. Several more died when tsunami waves swamped an island off the country's coast.

Chile is no stranger to violent jolts. In fact, USGS geophysicist Ross Stein called the country an "earthquake hatchery." Thirteen temblors of magnitude 7 or larger have hit Chile since 1973.

智利附近海域日前遭遇特大地震，据专家介绍，此次地震属于超级大地震中的“顶尖级别”，与2004年那场引发致命海啸的印度洋地震不相上下。

智利发生的这场里氏8.8级大地震属于“大逆冲型地震”，只有当一个地壳板块俯冲至另一板块的下方时才会发生，被认为是地球上威力最强的地震。据美国地质调查局国家地震信息中心统计，上周六发生于智利的地震释放了大约500亿吨能量，而且造成约340英里长的断层带破裂。

此次地震的震中位于海上，位于史上规模最大的、发生于1960年的智利9.5级地震的震中以北140英里处。这场地震造成约1600人遇难，并造成太平洋海域的很多人丧生。

美国地质调查局的地质学家布莱恩．阿特沃特说：“这场地震属于超级大地震中的顶尖等级。”

如果按照震级来划分，这次地震将与1906年发生于厄瓜多尔附近海域的地震并列为1900年以来的第五大地震。

美国地质调查局的地球物理学家肯．赫德纳特说：“我们称它们为超级地震，它们的力量十分可怕。这种级别的地震不是很多。”

与2004年苏门答腊岛发生的里氏9.1级地震相比，此次智利地震的规模相对较小，据估计其破坏性也相去甚远。2004年的苏门答腊岛地震及其引发的海啸导致23万人丧生。另一个区别在于，提前数小时发布的海啸预警让夏威夷和太平洋岛屿的居民有了充分的逃命时间。

而2004年，由于勘测技术有限，无法向印度洋国家发出大规模海啸袭击的预警。

当天，智利还发生了100多次里氏5级或更大级别的余震。截至目前，地震死亡人数已超过300，而这一数字还有可能会继续上升。地震引发的海啸还席卷了智利附近海域的一个岛屿，造成数人死亡。

智利是个大地震多发的国家。美国地质调查局地球物理学家罗斯．斯坦称其为“地震孵化器”。自1973年以来，智利共发生了13次里氏7级或更高级别的地震。

Vocabulary:

temblor：earthquake（地震）

tectonic plate：地层，地壳板块

fault zone：断层

swamp：to flood or drench with water or the like（淹没，覆没）