However, it has recently been shown that they are not hot and that they owe their low seismic velocities to their distinct composition.

These reflectors represent a change in rock properties across a boundary between two layers of rock, particularly seismic velocity and density.

The 'Minus' component helps determine the seismic velocity of the refractive medium.

For a complete model of the Earth, mineral physics is needed to interpret seismic velocities in terms of composition.

As well, a very good model of the local crustal velocity structure is required: seismic velocities vary with the local geology.

The core does not allow shear waves to pass through it, while the speed of travel (seismic velocity) is different in other layers.

The changes in seismic velocity between different layers causes refraction owing to Snell's law, like light bending as it passes through a prism.

Likewise, reflections are caused by a large increase in seismic velocity and are similar to light reflecting from a mirror.

Low seismic attenuation, and high seismic velocities characterize this region.

Today the zone is marked by relatively high heat flow and low seismic velocities in the crust.