Joint inversion of surface wave velocity and gravity observations and its application to central Asian basins shear velocity structure
Joint inversion of surface wave velocity and gravity observations and its application to central Asian basins shear velocity structure
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DOI：
10.1029/2007jb005157
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发表时间：
2009-02
影响因子：
--
通讯作者：
M. Maceira;C. Ammon
中科院分区：
文献类型：
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作者：
M. Maceira;C. Ammon
我们实现并应用了一种面波群速度与重力异常观测联合反演的方法。面波频散测量对地震横波速度敏感，重力测量对岩石密度变化提供了约束。我们的目标是获得一个自洽的三维剪切速度-密度模型，提高浅层地质结构的分辨率。本文应用该方法研究了塔里木盆地和准噶尔盆地两个中亚大型沉积盆地的地壳和上地幔结构。这些盆地有厚厚的沉积物，产生了大量的区域重力变化（高达几百毫克）。我们使用了从重力恢复和气候实验（GRACE）卫星任务导出的全球重力模型中提取的重力观测数据。我们将重力异常与高分辨率表面波慢度层析图结合起来，提供了中亚地区网格位置在8到100秒之间的群速度弥散值。为了整合这些数据，我们使用了由两个经验关系组合而成的地震速度和密度之间的关系。一个是由纳夫和德雷克确定的，最适用于沉积岩，另一个是线性的伯奇定律，更适用于密度较大的岩石（基底）。采用包含平滑的迭代阻尼最小二乘反演，以剪切速度变化作为主要模型参数，对两个数据集进行联合建模。结果表明塔里木盆地下部上地幔剪切速度较高，表明塔里木东西部下地壳和上地幔剪切速度存在差异。
[1] We implement and apply a method to the jointly inverted of surface wave group velocities and gravity anomalies observations. Surface wave dispersion measurements are sensitive to seismic shear wave velocities, and the gravity measurements supply constraints on rock density variations. Our goal is to obtain a self-consistent three-dimensional shear velocity–density model with increased resolution of shallow geologic structures. We apply the method to investigate the structure of the crust and upper mantle beneath two large central Asian sedimentary basins: the Tarim and Junggar. The basins have thick sediment sections that produce substantial regional gravity variations (up to several hundred milligals). We used gravity observations extracted from the global gravity model derived from the Gravity Recovery and Climate Experiment (GRACE) satellite mission. We combine the gravity anomalies with high-resolution surface wave slowness tomographic maps that provide group velocity dispersion values in the period range between 8 and 100 s for a grid of locations across central Asia. To integrate these data, we use a relationship between seismic velocity and density constructed through the combination of two empirical relations. One determined by Nafe and Drake, most appropriate for sedimentary rocks, and a linear Birch's law, more applicable to denser rocks (the basement). An iterative, damped least squares inversion including smoothing is used to jointly model both data sets, using shear velocity variations as the primary model parameters. Results show high upper mantle shear velocities beneath the Tarim basin and suggest differences in lower crust and upper mantle shear velocities between the eastern and western Tarim.