A global geoid model with imposed plate velocities and partial layering
A global geoid model with imposed plate velocities and partial layering
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具有强加板块速度和部分分层的全局大地水准面模型
DOI：
10.1029/1999jb900150
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发表时间：
1999
影响因子：
--
通讯作者：
L. Fleitout
中科院分区：
文献类型：
--
作者：
O. Čadek;L. Fleitout
迄今为止，大多数长波大地水准面与地震层析成像资料的反演都是在纯全地幔或完全层状环流的假设下进行的。此外，将岩石圈建模为具有均匀低粘度的球壳，发现与观测到的大地水准面最吻合。我们已经测试了是否可以通过包括两个约束条件来实现良好的大地水准面预测：660公里不连续的半渗透行为和与观测到的速度相等的地表板块速度。上下地幔之间的质量传递是通过施加660公里深度的表面密度异常而改变的，这与实现完美分层环流所需的质量异常成正比。在地幔的顶部，我们假设有一个坚硬的岩石圈，它以与观测到的板块运动相对应的速度运动。粘度只随深度而变化。考虑到简单的三层粘度结构和改变660-km界面的渗透率，我们获得了令人满意的大地水准面数据方差减少（2-12度约75%）。与纯全地幔模型相比，如果将660 km边界上的传质量减少到三分之一，则与大地水准面拟合最佳。最适合的黏度剖面特征是软流圈的清晰定义和下地幔黏度至少增加2个数量级。我们的模型预测的动态地形振幅非常小（~ 100 m），因此与观测完全一致。
Most inversions of the long-wavelength geoid in conjunction with the seismic tomographic information have so far been carried out under the assumption of either purely whole mantle or perfectly layered circulation. Moreover, modeling the lithosphere as a spherical shell with a uniform low viscosity was found to yield the best fit to the observed geoid. We have tested whether a good prediction of the geoid can also be achieved by including two constraints: a semipermeable behavior of the 660-km discontinuity and surface plate velocities equal to the observed ones. The mass transfer between upper and lower mantle has been changed by imposing a surface density anomaly at a depth of 660 km, which is proportional to the mass anomaly needed to achieve perfectly layered circulation. On the top of the mantle we assume a stiff lithosphere that moves with a velocity corresponding to the observed plate motion. The viscosity only varies with depth. Considering a simple three-layer viscosity structure and changing the permeability of the 660-km interface, we have obtained a satisfactory variance reduction of the geoid data (∼75% for degrees 2–12). The best fit to the geoid is obtained if the mass transfer across the 660-km boundary is reduced to one third in comparison with the purely whole mantle model. The best fitting viscosity profile is characterized by a clearly defined asthenosphere and a viscosity increase by at least 2 orders of magnitude in the lower mantle. The amplitudes of dynamic topography predicted by our model are remarkably small (∼100 m), thus fully compatible with the observation.