< p > tldr;<强>增加密度符合减少纵波速度< /强> < / p > < p >的纵波速度各向同性介质是:< / p > < p > <跨类= " math-container " > $ $ V_p = \√6 \压裂{K + 4/3 \μ}{\ρ}$ $ < / span > < / p > < p >, < span class = " math-container " > K < / span >美元是体积弹性模量,< span class = " math-container " > \μ< / span >美元是剪切模量,和<跨类= " math-container " > \ρ< / span >是美元密度(< a href = " https://en.wikipedia.org/wiki/Elastic_modulus " rel = " nofollow noreferrer " > https://en.wikipedia.org/wiki/Elastic_modulus < / >,见< span class = " math-container " > $ M $ < / span > p波模量)。岩石各向同性就意味着压力引起的压力是不分方向的压力。检查方程可以看出,<强>增加密度符合减少速度< /强>。< / p > < p >在地幔中,< span class = " math-container " > \ρ< / span >美元随深度增加,但分子类< span = " math-container " > $ K + 4/3 \μ$ < / span >增加速度比< span class = " math-container " > \ρ< / span >美元,净效应是增加速度。< / p > < p >的< /强> <强>液体外核,< span class = " math-container " > \μ= 0美元< / span >。这是因为流体不支持剪切应力。相应地,< span class = " math-container " > V_p < / span >美元急剧下降。< / p >In the solid inner core, $\mu$ is nonzero hence there is a jump in velocity at the inner/outer core boundary. The combination of $K$, $\mu$, and $\rho$ in the inner core is such that $V_p$ doesn't exceed the lower mantle values.