什么是 Lithosphere, asthenosphere, low-velocity zone？

The lithosphere is the rigid outer shell of the Earth, the crust and the uppermost mantle, which behaves as a strong layer over geological times and is divided into plates. The asthenosphere is the weaker layer of the upper mantle below it, which deforms by slow flow and lets the plates move. The low-velocity zone is the depth range below the lithosphere where the seismic speeds, S speeds especially, are lower than just above and below.