The earth has more mass and so part of this density is attributable to gravitational compression.
地球有更多的质量和密度， 使这部分是由于引力压缩。
2
The other two, Primary (P) or compression waves and Secondary (S) or shear waves, penetrate the interior of the Earth.
另外两种，P或者“压缩波”以及S“剧烈波”，穿透地球内部。
3
The results show that a certain amount of the mixed rare earth oxide content in the batch can increase the cold compression strength and the thermal shock resistance of the bricks.