The most remarkable feature of the upper mantle is the low-velocity zone. as suggested by its name, this is a region in the upper mantle in which there is a decrease in the speed of seismic wave.

• 上地幔一个最显著的现象就是低速带，就像这个词名所表达的那样，在上地幔存在这么一个区域，在那里地震波波速会发生减慢。