On the robustness of estimates of mechanical anisotropy in the continental lithosphere: A North American case study and global reanalysis
On the robustness of estimates of mechanical anisotropy in the continental lithosphere: A North American case study and global reanalysis
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DOI：
10.1016/j.epsl.2015.02.041
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发表时间：
2015-06
影响因子：
5.3
通讯作者：
L. Kalnins;F. Simons;J. Kirby;Dong V. Wang;S. Olhede
中科院分区：
文献类型：
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作者：
L. Kalnins;F. Simons;J. Kirby;Dong V. Wang;S. Olhede
岩石圈强度的变化既影响着许多构造过程，也受到许多构造过程的影响，包括造山和裂谷旋回。大陆岩石圈漫长、复杂和高度各向异性的历史可能导致普遍存在机械各向异性的自然预期。地形和重力异常之间的一致性确实存在各向异性，但它是否对应于各向异性的弹性厚度仍存在疑问。如果相干性被用来估计岩石圈的弯曲强度，只有当相干性和由此得到的弹性强度都存在显著的各向异性，并且如果数据本身的各向异性的干扰可以可信地排除时，弹性各向同性的零假设才能被拒绝。我们考虑了用多锥度和小波方法进行的相干估计，并由此得到了有效弹性厚度的估计。我们开发了一系列各向异性的统计和地球物理测试，并特别评估了使用合成数据得出虚假结果的可能性。我们的主要案例研究是北美大陆，它的机械强度没有表现出有意义的各向异性。同样，使用多锥度方法对大陆重力和地形进行全球重新分析，只得出了很少的岩石圈弯曲各向异性的证据。
Lithospheric strength variations both influence and are influenced by many tectonic processes, including orogenesis and rifting cycles. The long, complex, and highly anisotropic histories of the continental lithosphere might lead to a natural expectation of widespread mechanical anisotropy. Anisotropy in the coherence between topography and gravity anomalies is indeed often observed, but whether it corresponds to an elastic thickness that is anisotropic remains in question. If coherence is used to estimate flexural strength of the lithosphere, the null-hypothesis of elastic isotropy can only be rejected when there is significant anisotropy in both the coherence and the elastic strengths derived from it, and if interference from anisotropy in the data themselves can be plausibly excluded. We consider coherence estimates made using multitaper and wavelet methods, from which estimates of effective elastic thickness are derived. We develop a series of statistical and geophysical tests for anisotropy, and specifically evaluate the potential for spurious results with synthetically generated data. Our primary case study, the North American continent, does not exhibit meaningful anisotropy in its mechanical strength. Similarly, a global reanalysis of continental gravity and topography using multitaper methods produces only scant evidence for lithospheric flexural anisotropy.