Due to relatively high terrain and negligible active tectonics, the southern Africa region boasts over 30 independent estimates of dynamic topography. These published estimates display a wide variance due to both the variety of methods used in computation and a lack of constraints on the regional mantle structure. Here we show that a focus on regional mantle structure is important to generate models of lithospheric and mantle dynamics. Global average mantle properties are not representative of a particular region, and it is necessary to generate viscosity profiles specific to a region of interest. We develop a Bayesian inversion using dynamic geoid kernels, existing seismic tomography models, and Slepian functions to invert for a localized radial viscosity profile that best explains the geoid in southern Africa. With an understanding of viscosity uncertainty, we constrain dynamic topography in southern Africa to lie between 1,000 and 2,000 m. Additionally, we model vertical displacements from 112 Global Navigation Satellite System stations across our region to examine the long-term, long wavelength pattern of present-day vertical motion, suggesting that a mean of 1.5 mm/yr (1$\sigma$: 0.8–2.0 mm/yr) of vertical motion may be related to ongoing dynamic topography. Our study demonstrates the utility of dynamic geoid kernels in local nonlinear inversions of non-unique geophysical data. Furthermore, we present evidence that the mantle beneath southern Africa is generating significant dynamic support for and vertical displacement of the lithosphere in this region.

中文翻译：

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地幔结构对南部非洲动态地形的影响


由于相对较高的地形和可以忽略不计的活跃构造，南部非洲地区拥有 30 多个独立的动态地形估计。这些已发表的估计显示出很大的差异，因为计算中使用的方法多种多样，而且缺乏对区域地幔结构的约束。在这里，我们表明，关注区域地幔结构对于生成岩石圈和地幔动力学模型非常重要。全局平均地幔特性不能代表特定区域，因此需要生成特定于感兴趣区域的粘度曲线。我们使用动态大地水准面核、现有的地震断层扫描模型和 Slepian 函数开发贝叶斯反演，以获得最能解释南部非洲大地水准面的局部径向粘度曲线。在了解粘度不确定性的基础上，我们将南部非洲的动态地形限制在 1,000 到 2,000 m 之间。此外，我们对我们地区 112 个全球导航卫星系统站的垂直位移进行建模，以检查当今垂直运动的长期、长波长模式，表明平均 1.5 毫米/年（1$\sigma$：0.8-2.0 毫米/年）的垂直运动可能与持续的动态地形有关。我们的研究证明了动态大地水准面核在非唯一地球物理数据的局部非线性反演中的效用。此外，我们提供了证据表明，南部非洲下方的地幔正在为该地区的岩石圈产生重要的动态支撑和垂直位移。