最下层地幔因地震异性变形而变形
Andy Nowacki1, James Wookey, J-Michael Kendall
1Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol, BS8 1RJ, UK. andy.nowacki@bristol.ac.uk
Nature
|October 29, 2010
概括
地球D′′层的地震异构性表明MgSiO(3) 在矿后变形. 新的测量揭示了复杂的机制是必要的解释地震波分裂,指向剪切 (001) 作为一个可能的原因.
科学领域:
- 地质物理学 地质物理学
- 地震学 地震学
- 矿物物理 矿物物理
背景情况:
- 地球的最下层地幔 (D′′) 呈现出显著的地震异构性.
- 这种异质性很可能是由于MgSiO(3) -后矿 (ppv) 的对齐造成的,这是主要的矿物阶段.
- 之前的异质性测量范围有限,阻碍了对ppv变形机制的理解.
研究的目的:
- 为了研究北美和中美洲下方的D"层的地震异构性.
- 在MgSiO(3) -ppv中区分候选滑动机制.
- 提高对核心-地幔边界的变形过程的理解.
主要方法:
- 用浅层和深层地震测量D"层中剪波分裂的测量.
- 获取了三个区域的700多个测量结果,增加了亚齐图斯覆盖范围.
- 对观察到的地震数据进行各种MgSiO(3) -ppv变形机制的测试.
主要成果:
- 以前假设的D′′的垂直横向同变性模型没有得到数据的支持.
- 需要更复杂的变形机制来解释观察到的地震异构性.
- 在MgSiO ((3) -ppv的 (001) 平面上发生剪切是观察到的异质性最一致的解释.
结论:
- 这些发现挑战了D"层中地震异性质的简单模型.
- 切割 (001) 被确定为MgSiO ((3) -ppv.最可能的变形机制.
- 这项研究为绘制核心-地幔边界变形的路径提供了途径,并将D′′过程与地幔动力学联系起来.
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