Continental topography is dominantly controlled by a combination of crustal thickness and density variations. Nevertheless, it is clear that some additional topographic component is supported by the buoyancy structure of the underlying lithospheric and convecting mantle. Isolating these secondary sources is not straightforward, but provides valuable information about mantle dynamics. Here, we estimate and correct for the component of topographic elevation that is crustally supported to obtain residual topographic anomalies for the major continents, excluding Antarctica. Crustal thickness variations are identified by assembling a global inventory of 26,725 continental crustal thickness estimates from local seismological data sets (e.g., wide-angle/refraction surveys, calibrated reflection profiles, receiver functions). In order to convert crustal seismic velocity into density, we develop a parametrization that is based upon a database of 1,136 laboratory measurements of seismic velocity as a function of density and pressure. In this way, 4,120 new measurements of continental residual topography are obtained. Observed residual topography mostly varies between ±1 and 2 km on wavelengths of 1,000–5,000 km. Our results are generally consistent with the pattern of residual depth anomalies observed throughout the oceanic realm, with long-wavelength free-air gravity anomalies, and with the distribution of upper mantle seismic velocity anomalies. They are also corroborated by spot measurements of emergent marine strata and by the global distribution of intraplate magmatism that is younger than 10 Ma. We infer that a significant component of residual topography is generated and maintained by a combination of lithospheric thickness variation and sub-plate mantle convection. Lithospheric composition could play an important secondary role, especially within cratonic regions.

中文翻译：

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从地壳结构的全球分析中提取的大陆残余地形

大陆地形主要由地壳厚度和密度变化的组合控制。然而，很明显，一些额外的地形成分是由底层岩石圈和对流地幔的浮力结构支持的。分离这些次要来源并不简单，但提供了有关地幔动力学的宝贵信息。在这里，我们估计并校正地壳支撑的地形高程分量，以获得主要大陆（不包括南极洲）的残余地形异常。地壳厚度变化是通过根据当地地震数据集（例如广角/折射调查、校准反射剖面、接收器函数）汇总 26,725 个大陆地壳厚度估计值的全球清单来识别的。为了将地壳地震速度转换为密度，我们开发了一种基于数据库的参数化方法，该数据库包含 1,136 个地震速度实验室测量值，作为密度和压力的函数。这样，就获得了4120个新的大陆残余地形测量数据。观测到的残余地形在 1,000–5,000 km 波长上的变化大多在 ±1 到 2 km 之间。我们的结果总体上与整个海洋领域观测到的残余深度异常模式、长波长自由空气重力异常以及上地幔地震速度异常的分布一致。这些结论还得到了浮现海洋地层的点测量和小于 10 Ma 的板内岩浆作用的全球分布的证实。我们推断，残余地形的一个重要组成部分是由岩石圈厚度变化和板下地幔对流的结合产生和维持的。岩石圈成分可能发挥重要的次要作用，特别是在克拉通地区。