Mapping the evolving strain field during continental breakup from crustal anisotropy in the Afar Depression.
Mapping the evolving strain field during continental breakup from crustal anisotropy in the Afar Depression.
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DOI：
10.1038/ncomms1287
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发表时间：
2011
影响因子：
16.6
通讯作者：
Rowland, J. V.
中科院分区：
文献类型：
--
作者：
Keir, Derek;Belachew, M.;Ebinger, C. J.;Kendall, J. -M.;Hammond, J. O. S.;Stuart, G. W.;Ayele, A.;Rowland, J. V.
导致板块破裂的大陆裂谷是由机械变形和岩浆侵入共同发生的，但这些替代机制局部化拉伸应变的空间和时间尺度仍然存在争议。在这里，我们使用当地地震的剪切波分裂来量化火山活跃的阿法尔三重交界处上地壳的各向异性，以评估大陆破裂区域的应变分布和方向。阿法尔地区横波分裂的模式最好用变形相关结构的各向异性来解释，由于堤坝引起的断层密度增加，加上火山中心附近定向熔池的贡献，裂谷轴的分裂参数发生了巨大变化。岩石圈中缺乏裂谷垂直各向异性，并且证实了以堤围为主的扩张的地球科学证据，提供了强有力的证据，表明岩浆侵入在该早期板块破裂区域实现了大部分板块打开。 机械变形和岩浆侵入导致大陆破裂的时空尺度仍然存在争议。凯尔等人。使用地震中的 S 波分裂来量化阿法尔三重交界处的各向异性，以评估大陆破裂区域的应变。
Rifting of the continents leading to plate rupture occurs by a combination of mechanical deformation and magma intrusion, yet the spatial and temporal scales over which these alternate mechanisms localize extensional strain remain controversial. Here we quantify anisotropy of the upper crust across the volcanically active Afar Triple Junction using shear-wave splitting from local earthquakes to evaluate the distribution and orientation of strain in a region of continental breakup. The pattern of S-wave splitting in Afar is best explained by anisotropy from deformation-related structures, with the dramatic change in splitting parameters into the rift axis from the increased density of dyke-induced faulting combined with a contribution from oriented melt pockets near volcanic centres. The lack of rift-perpendicular anisotropy in the lithosphere, and corroborating geoscientific evidence of extension dominated by dyking, provide strong evidence that magma intrusion achieves the majority of plate opening in this zone of incipient plate rupture. The spatial and temporal scales over which continental breakup occurs by mechanical deformation and magma intrusion remain controversial. Keir et al. quantify anisotropy across the Afar Triple Junction using S-wave splitting from earthquakes to evaluate the strain in a region of continental breakup.
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