GyPSuM: A joint tomographic model of mantle density and seismic wave speeds
GyPSuM: A joint tomographic model of mantle density and seismic wave speeds
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DOI：
10.1029/2010jb007631
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发表时间：
2010-12-01
影响因子：
3.9
通讯作者：
Grand, Stephen P.
中科院分区：
文献类型：
--
作者：
Simmons, Nathan A.;Forte, Alessandro M.;Grand, Stephen P.
GyPSuM是地幔横波（S）速度、纵波（P）速度和密度的三维模型。该模型是通过同时反演地震体波走时（P和S）和地球动力学观测，同时使用现实的矿物物理参数连接波速和密度。地球动力学观测包括全球自由空气重力场、构造板块的辐散、自由表面的动力学地形和流动引起的核幔边界的超椭圆率。GyPSuM的理念是，最接近热变化的异质性是最简单的解决方案。来自地球自由振荡的密度场模型为地幔的密度结构提供了很好的见解，但仅限于非常长的波长解决方案。或者，缩放更高分辨率的地震图像以获得密度异常产生不满足地球动力学观测的密度场。目前的研究提供了一个三维密度模型的地幔，直接满足地球动力学和地震观测，通过联合地震地球动力学反演过程。值得注意的密度场观测包括超级羽流结构底部的高密度堆，支持过去正常模式研究的一般结果。然而，我们发现，这些功能更本地化，并具有较低的幅度比过去的研究将建议。当我们考虑GyPSuM的快、慢地震异常时，我们发现P波和S波速度在整个地幔中有很强的相关性。然而，我们发现，在深地幔（>1500公里深度）的快S波带与相应的P波异常的相关性较低，这表明在古代俯冲板片异常的简化热效应的系统性分歧。超声波岩石圈和D "区显示出强烈的成分特征。然而，我们认为，温度的变化是主要原因的P波速度，S波速度，和密度异常的大部分地幔。
GyPSuM is a 3-D model of mantle shear wave (S) speeds, compressional wave (P) speeds, and density. The model is developed through simultaneous inversion of seismic body wave travel times (P and S) and geodynamic observations while using realistic mineral physics parameters linking wave speeds and density. Geodynamic observations include the global free air gravity field, divergence of the tectonic plates, dynamic topography of the free surface, and the flow-induced excess ellipticity of the core-mantle boundary. GyPSuM is built with the philosophy that heterogeneity that most closely resembles thermal variations is the simplest possible solution. Models of the density field from Earth's free oscillations have provided great insight into the density configuration of the mantle but are limited to very long wavelength solutions. Alternatively, scaling higher-resolution seismic images to obtain density anomalies generates density fields that do not satisfy geodynamic observations. The current study provides a 3-D density model for the mantle that directly satisfies geodynamic and seismic observations through a joint seismic-geodynamic inversion process. Notable density field observations include high-density piles at the base of superplume structures, supporting the general results of past normal mode studies. However, we find that these features are more localized and have lower amplitude than past studies would suggest. When we consider both fast and slow seismic anomalies in GyPSuM, we find that P and S wave speeds are strongly correlated throughout the mantle. However, we find a low correlation of fast S wave zones in the deep mantle (>1500 km depth) with the corresponding P wave anomalies, suggesting a systematic divergence from simplified thermal effects in ancient subducted slab anomalies. The cratonic lithosphere and D '' regions are shown to have strong compositional signatures. However, we argue that temperature variations are the primary cause of P wave speed, S wave speed, and density anomalies throughout most of the mantle.