Fault and graben growth along active magmatic divergent plate boundaries in Iceland and Ethiopia
Fault and graben growth along active magmatic divergent plate boundaries in Iceland and Ethiopia
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冰岛和埃塞俄比亚沿活跃岩浆发散板块边界的断层和地堑生长
DOI：
10.1002/2015tc003991
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发表时间：
2015
期刊：
影响因子：
4.2
通讯作者：
B. Abebe
中科院分区：
文献类型：
--
作者：
D. Trippanera;V. Acocella;J. Ruch;B. Abebe
最近的研究强调了沿岩浆扩张板块边界（MDPB）活动轴发育正断层和地堑的年尺度岩脉裂陷事件的重要性。然而，长期（102-105年）筑堤对MDPB累积地表变形和演化的作用尚不清楚。为了更好地了解沿MDPB轴线的长期正断层和地堑，我们分析了冰岛和埃塞俄比亚的裂缝群。我们首先关注的是最简单的未成熟裂缝群，即单岩脉喷发裂缝；这是一个小于1公里宽的地堑，与正断层接壤，位移可达几米，与理论模型和大地测量数据一致。发现了类似的构造模式，在更宽的成熟裂缝群中发现了不对称和多个地堑，这些裂缝群由几个岩脉喷发裂缝形成。然后，我们考虑沿这些地堑的正断层的横向终止，以检测它们向上或向下的传播。大部分断层以平面上的开缝终止，表明断层向下扩展；这与最近的实验结果一致，表明岩脉引起的正断层从地表向下传播。然而，一些正断层也终止于单线上的开放裂缝，类似于断层传播褶皱；这表明被重新激活的隐伏断层向上传播，这是由筑坝推动的。这些结果表明，断层的生长和地堑的发育，以及MDPB轴线的长期演化，可能只能通过脉位来解释，而不需要任何岩浆断层作用。
Recent studies highlight the importance of annual‐scale dike‐induced rifting episodes in developing normal faults and graben along the active axis of magmatic divergent plate boundaries (MDPB). However, the longer‐term (102–105 years) role of diking on the cumulative surface deformation and evolution of MDPB is not yet well understood. To better understand the longer‐term normal faults and graben along the axis of MDPB, we analyze fissure swarms in Iceland and Ethiopia. We first focus on the simplest case of immature fissure swarms, with single dike‐fed eruptive fissures; these consist of a <1 km wide graben bordered by normal faults with displacement up to a few meters, consistent with theoretical models and geodetic data. A similar structural pattern is found, with asymmetric and multiple graben, within wider mature fissure swarms, formed by several dike‐fed eruptive fissures. We then consider the lateral termination of normal faults along these grabens to detect their upward or downward propagation. Most faults terminate as open fractures on flat surface, suggesting downward fault propagation; this is consistent with recent experiments showing dike‐induced normal faults propagating downward from the surface. However, some normal faults also terminate as open fractures on monoclines, which resemble fault propagation folds; this suggests upward propagation of reactivated buried faults, promoted by diking. These results suggest that fault growth and graben development, as well as the longer‐term evolution of the axis of MDPB, may be explained only through dike emplacement and that any amagmatic faulting is not necessary.
影响因子：
5.8
作者：
Keir, Derek;Hamling, Ian J.;Bennati, Laura
通讯作者：
Bennati, Laura
影响因子：
2.8
作者：
Ebinger, C. J.;Keir, D.;Buck, W. R.
通讯作者：
Buck, W. R.