Seismic evidence for widespread western-US deep-crustal deformation caused by extension
Seismic evidence for widespread western-US deep-crustal deformation caused by extension
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DOI：
10.1038/nature08951
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发表时间：
2010-04
期刊：
影响因子：
64.8
通讯作者：
M. Moschetti;M. Moschetti;M. Ritzwoller;F. Lin;Yingjie Yang
中科院分区：
文献类型：
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作者：
M. Moschetti;M. Moschetti;M. Ritzwoller;F. Lin;Yingjie Yang
实验室实验已经证实，构成地球的许多材料在地震波速度方面具有很强的各向异性。对上地幔中方位角和径向各向异性的观测归因于与变形相关的剪切应变引起的橄榄石的晶格择优取向，并为地球内部的变形和流动提供了一些最直接的证据。尽管地壳径向各向异性的观测将提高我们对构造过程引起的地壳变形和流动模式的理解，但大规模观测仅限于地壳特别厚的区域。在这里，我们表明，美国西部环境噪声断层扫描的观测结果揭示了强烈的深部（中到下）地壳径向各向异性，该各向异性主要局限于新生代时期（自 65 Myr 前）经历了显着扩张的地质省份。地壳径向各向异性与美国西部伸展区的重合表明，径向各向异性是由伸展变形引起的各向异性地壳矿物的晶格择优取向造成的。这些观测结果还支持以下假设：这些区域内的深地壳因地壳变薄和扩张而经历了广泛且相对均匀的应变。
Laboratory experiments have established that many of the materials comprising the Earth are strongly anisotropic in terms of seismic-wave speeds. Observations of azimuthal,and radial,anisotropy in the upper mantle are attributed to the lattice-preferred orientation of olivine caused by the shear strains associated with deformation, and provide some of the most direct evidence for deformation and flow within the Earth’s interior. Although observations of crustal radial anisotropy would improve our understanding of crustal deformation and flow patterns resulting from tectonic processes, large-scale observations have been limited to regions of particularly thick crust. Here we show that observations from ambient noise tomography in the western United States reveal strong deep (middle to lower)-crustal radial anisotropy that is confined mainly to the geological provinces that have undergone significant extension during the Cenozoic Era (since ∼65 Myr ago),. The coincidence of crustal radial anisotropy with the extensional provinces of the western United States suggests that the radial anisotropy results from the lattice-preferred orientation of anisotropic crustal minerals caused by extensional deformation. These observations also provide support for the hypothesis that the deep crust within these regions has undergone widespread and relatively uniform strain in response to crustal thinning and extension,,.