Formation and growth of normal faults at the divergent plate boundary in Iceland
Formation and growth of normal faults at the divergent plate boundary in Iceland
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DOI：
10.1111/j.1365-3121.1992.tb00582.x
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发表时间：
1992-04
期刊：
影响因子：
2.4
通讯作者：
A. Gudmundsson
中科院分区：
文献类型：
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作者：
A. Gudmundsson
冰岛的扩张板块边界以40-80 km长、5-10 km宽的张性断裂群（长约102 m）和正断层群（长约103 m）为特征。地壳上部主要由熔岩流组成，有丰富的柱状节理，大多垂直于熔岩接触面。熔岩流在裂谷带的表面是水平的，但在地壳中每150米深处以1°的速率倾斜。在裂谷带的地表，节理是垂直的，并平行于垂直主应力。由于熔岩堆的倾斜，柱状节理变得倾斜于该应力，因此成为潜在的剪切断裂，并在地壳更深处形成梯队。理论研究表明，正断层在地壳深度为0.5-1.5 km的雁列柱状节理和/或大规模张性断裂上开始成核。宽度（深度）必须是许多断层的最小（控制）尺寸。全新世断层的最大落差与断层长度之间存在线性正相关关系（r = 0.91）。如果断层以自相似结构生长，则断层长度和宽度之间的相似关系可以解释断层落差-长度关系。
The divergent plate boundary in Iceland is characterized by 40–80 km long and 5–10 km wide swarms of tension fractures (∼102 m long) and normal faults (∼103 m long). The upper part of the crust is mainly composed of lava flows, with abundant columnar joints that are mostly perpendicular to the lava contacts. The lava flows are horizontal at the surface of the rift zone but become tilted at the rate of 1° for every 150 m depth in the crust. At the surface of the rift zone the joints are vertical and parallel to the vertical principal stress. Because of tilting of the lava pile, the columnar joints become oblique to this stress, hence becoming potential shear fractures, and form echelon sets at greater depths in the crust. Theoretical considerations suggest that normal faults start to nucleate on sets of en echelon columnar joints and/or large-scale tension fractures at crustal depths of 0.5–1.5 km. The width (depth) must be the smallest (controlling) dimension of many faults. Nevertheless, there is a positive linear relation (r = 0.91) between maximum throw and length of the Holocene faults. If the faults grow as self-similar structures, the throw-length relationship can be explained by a similar relation between fault length and width.