A low-velocity zone has a wave-speed decrease with depth over some interval. Surface rays do not turn within its negative-gradient interior; rays penetrating it can return only after encountering sufficient speed recovery below. This can produce shadow ranges, multiple travel-time branches and poor turning-depth coverage. A wave-specific low-velocity zone is not identical to a mechanical layer boundary.
A low-velocity zone (LVZ) is a specific region within the Earth's interior, typically found in the upper mantle, characterized by a significant reduction in seismic wave velocities compared to surrounding areas. These zones are often associated with certain geological and tectonic features, such as subduction zones, hotspots, and the presence of partially melted rock.
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