Isostasy and flexure of the lithosphere under the Hawaiian Islands
Isostasy and flexure of the lithosphere under the Hawaiian Islands
复制标题
夏威夷群岛岩石圈的均衡和弯曲
DOI：
10.1029/jb084ib10p05599
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发表时间：
1979
影响因子：
--
通讯作者：
W. Suyenaga
中科院分区：
文献类型：
--
作者：
W. Suyenaga
以前对夏威夷的挠曲研究是在假设岛屿载荷引起的挠曲量等于莫霍面深度变化的情况下进行的。基于地震折射的地壳剖面图表明，作为基底和海洋层之间边界深度变化的另一种偏转测量方法。这一备选方案意味着地壳存在一个未弯曲部分，代表基底-海洋位移和莫霍面位移之间的差异，并有效地减轻了浮力造成的载荷。这些物质要么代表地幔到地壳物质的相变，要么代表侵入下地壳。本文从挠曲和艾里等值线的基本方程出发，导出了一个更一般的平衡方程，它可以解释为在均衡方程中增加了弹性挠曲项，也可以解释为在目前使用的挠曲方程中增加了一个反映地壳柱变化的项。简单模型的研究表明，在估计抗弯刚度最可靠的参数是弯曲的波长。当弹性弯曲和浮力增加地壳被认为是在夏威夷洋脊在奥陶纪，一个合理的情况下，两者的存在。导出了夏威夷群岛未破裂岩石圈的抗弯刚度约为1.2×1023 N m，这一数值与其他研究结果一致。
Previous flexural studies on Hawaii were done under the assumption that the amount of deflection caused by the loading of the islands is equivalent to the change in Moho depth. Crustal profiles based on seismic refraction suggest an alternative measurement of deflection as the change in depth of the boundary between the basement and oceanic layers. This alternative implies the existence of an unflexed portion of the crust that represents the difference between the basement-oceanic and Moho displacements and that effectively lessens the load due to its buoyancy. This material represents either a phase change of mantle to crustal material or intrusion into the lower crust. From the basic equations of flexure and Airy isostasy a more general form of equilibrium equation is developed and can be interpreted as an addition of an elastic flexure term to the isostatic equations or an addition of a term accounting for changes in the crustal column to the presently used flexure equations. The study of simple models indicates that the most reliable parameter in estimating flexural rigidity is the wavelength of the flexure. When elastic flexure and buoyancy of added crust are considered in relation to the Hawaiian Ridge at Oahu, a plausible case is made for the presence of both. A flexural rigidity of about 1.2×1023 N m for an unfractured lithosphere is derived for the Hawaiian Islands; this value agrees favorably with results of other studies.