The lowermost mantle layer is above the core mantle boundary (CMB) and composed of D" region and ultra-low velocity zone (ULVZ)."

地幔底层由具有高地震波速和高密度的D″区和超低速带（ULVZ）组成。

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The lowermost mantle layer is above the core mantle boundary (CMB) and composed of D" region and ultra-low velocity zone (ULVZ)."

地幔底层由具有高地震波速和高密度的D″区和超低速带（ULVZ）组成。

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