But geophysicists had thought that great subduction-zone earthquakes happened only where younger oceanic crust scrapes its way into the mantle.

但是在此之前，地球物理学者们认为，这种俯冲带大地震仅仅在年轻的海洋地壳挤入地幔处才可能发生。

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In subduction zones, where older and colder oceanic crust descends beneath another tectonic plate, Deep focus earthquakes may occur at much greater depths (up to seven hundred kilometers).

在隐没带，当更老的和更冷的海洋地壳下降到另一个构造板块下面时，深震源地震可能会发生在非常深的深度(达到700公里)。

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