Motion in the north Iceland volcanic rift zone accommodated by bookshelf faulting
Motion in the north Iceland volcanic rift zone accommodated by bookshelf faulting
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DOI：
10.1038/ngeo2012
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发表时间：
2014
影响因子：
18.3
通讯作者：
R. Green;R. White;T. Greenfield
中科院分区：
文献类型：
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作者：
R. Green;R. White;T. Greenfield
伸展的地壳沿沿着洋中脊以10至1 000公里的长度分段。在裂谷段彼此偏移的地方，段间的运动由与主裂谷轴正交的转换断层调节。在线段重叠的地方，具有各种几何形状的非变换偏移可适应剪切运动。在这里，我们使用微地震数据来分析断层的几何形状在冰岛北部的陆地上暴露在两个重叠的裂谷段。在裂谷段之间，我们发现了一系列与主裂谷方向平行的断层。这些断层通过左旋走滑运动滑动。然而，重叠的裂谷段之间的运动是通过右侧运动。这些运动共同导致断层和中间地壳块体顺时针旋转，这种运动与书架断层机制一致，因其类似于书架上倾斜的一排书而得名。断层可能重新激活了现有的地壳弱点，如岩脉侵入体，这些侵入体最初与主裂谷平行，后来顺时针旋转了约15°。与典型的大洋中脊转换断层相比，先前存在的平行裂谷弱点的重新激活是一个重要的例证，说明重叠裂谷段之间存在非转换偏移，可容纳剪切运动。
Along mid-ocean ridges the extending crust is segmented on length scales of 10–1,000 km. Where rift segments are offset from one another, motion between segments is accommodated by transform faults that are oriented orthogonally to the main rift axis. Where segments overlap, non-transform offsets with a variety of geometries accommodate shear motions. Here we use micro-seismic data to analyse the geometries of faults at two overlapping rift segments exposed on land in north Iceland. Between the rift segments, we identify a series of faults that are aligned sub-parallel to the orientation of the main rift. These faults slip through left-lateral strike-slip motion. Yet, movement between the overlapping rift segments is through right-lateral motion. Together, these motions induce a clockwise rotation of the faults and intervening crustal blocks in a motion that is consistent with a bookshelf-faulting mechanism, named after its resemblance to a tilting row of books on a shelf. The faults probably reactivated existing crustal weaknesses, such as dyke intrusions, that were originally oriented parallel to the main rift and have since rotated about 15° clockwise. Reactivation of pre-existing, rift-parallel weaknesses contrasts with typical mid-ocean ridge transform faults and is an important illustration of a non-transform offset accommodating shear motion between overlapping rift segments.