Oceanic detachment faults generate compression in extension
Oceanic detachment faults generate compression in extension
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DOI：
10.1130/g39232.1
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发表时间：
2017-10
期刊：
影响因子：
5.8
通讯作者：
R. Parnell‐Turner;R. Sohn;C. Peirce;T. Reston;C. MacLeod;R. Searle;N. Simão
中科院分区：
文献类型：
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作者：
R. Parnell‐Turner;R. Sohn;C. Peirce;T. Reston;C. MacLeod;R. Searle;N. Simão
在大洋中脊等伸展地质系统中，变形通常通过正断层上的滑动来调节，在那里，材料在张力下被拉开，应力在地震和岩浆增生期间通过破裂释放。然而，在缓慢扩张的大洋中脊，构造板块以244 000次的速度分离，在脊轴沿着25公里至海底10公里以下的深度探测到地震。令人惊讶的是，其中大多数是逆断层事件。仅限于海底以下3-7公里的深度，这些反向事件描绘了一个位于更深的伸展事件区附近的强烈挤压地震活动带。这种变形模式与岩石圈吸积过程中板块弯曲的挠曲模型是一致的。我们的研究结果表明，剥离下盘的下部经历压缩应力和内部变形的故障滚到低角度出现在海底之前。尽管拆离作用本身是一个伸展系统，但这些挤压应力触发了逆断层作用。
In extensional geologic systems such as mid-ocean ridges, deformation is typically accommodated by slip on normal faults, where material is pulled apart under tension and stress is released by rupture during earthquakes and magmatic accretion. However, at slowly spreading mid-ocean ridges where the tectonic plates move apart at rates 244,000 events detected along 25 km of the ridge axis, to depths of ∼10 km below seafloor. Surprisingly, the majority of these were reverse-faulting events. Restricted to depths of 3–7 km below seafloor, these reverse events delineate a band of intense compressional seismicity located adjacent to a zone of deeper extensional events. This deformation pattern is consistent with flexural models of plate bending during lithospheric accretion. Our results indicate that the lower portion of the detachment footwall experiences compressive stresses and deforms internally as the fault rolls over to low angles before emerging at the seafloor. These compressive stresses trigger reverse faulting even though the detachment itself is an extensional system.