为什么P波速度更高的下地幔比核心虽然核心有更高的密度?- 江南体育网页版- - - - -地球科学堆江南电子竞技平台栈交换 最近30从www.hoelymoley.com 2023 - 07 - 08 - t02:43:05z //www.hoelymoley.com/feeds/question/18529 https://creativecommons.org/licenses/by-sa/4.0/rdf //www.hoelymoley.com/q/18529 3 为什么P波速度更高的下地幔比核心虽然核心有更高的密度? 格雷格·沃尔什 //www.hoelymoley.com/users/18383 2019 - 11 - 21 - t23:25:29z 2019 - 11 - 23 - t01:41:03z < p >我刚开始教九年级地球科学和我的学生,我已经注意到一些关于p和S波深度和江南体育网页版速度图。在典型的图,如:< a href = " https://www.researchgate.net/figure/Earths-P-wave-velocity-S-wave-velocity-and-density-profiles-as-a-function-of-depth_fig8_280835886 " rel = " nofollow noreferrer " > https://www.researchgate.net/figure/Earths-P-wave-velocity-S-wave-velocity-and-density-profiles-as-a-function-of-depth_fig8_280835886 < / > < / p > < p > p波的速度从0公里深度策划深度6371公里它显示了p波速度达到约14公里/秒的时间到达底部的地幔。当然它急剧下降通过地幔/外核边界。然而,即使波到达内核,它的速度从未接近14公里/秒的速度,它的速度范围内/外核只从8到12公里/秒,即使核心比地幔密度要高得多。你会期望更高的波速。< / p > //www.hoelymoley.com/questions/18529/-/18536 # 18536 3 由dvoytan回答为什么P波速度更高下地幔的核心虽然核心有更高的密度? dvoytan //www.hoelymoley.com/users/18386 2019 - 11 - 23 - t01:41:03z 2019 - 11 - 23 - t01:41:03z < 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.

Baidu
map