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沿中央海岭,延伸的地壳以10~1 000km的尺度分段(MacDonald et al,1988)。在裂谷段相互错开的地方,段与段之间的运动由垂直于主裂谷轴方向的转换断层所容纳。在段叠加的地方,不同几何形状的非转换断层(Grindlay et al,1991)容纳剪切运动。这里,我们采用微震数据来分析冰岛北部出露的两个叠加裂谷段的断层几何形状。在这两个裂谷段之间,我们识别了沿主裂谷走向排列的一系列断层。这些断层为左旋走滑运动。而叠加裂谷段之间的运动则是右旋运动。这些运动一起产生了断层的顺时针旋转,致使地壳块体按书架型断层机制(类似于书架上倾斜放置的书的排列而得名)运动(Mandl,1987)。这些断层或许活化了已经存在的地壳软弱面,如原始走向平行于主裂谷并具有15°顺时针旋转的岩脉侵入体。先期存在、平行于裂谷的软弱面的活化与典型的中央海岭转换断层相反,说明非转换断层容纳着叠加段之间的剪切错动。
Along the central ridge, the extended crust is fragmented on a scale of 10-1 000 km (MacDonald et al., 1988). Where the rift sections are staggered from one another, the movement between the sections is accommodated by a transitional fault perpendicular to the main rift axis. Where segments are superimposed, non-transformed faults of different geometries (Grindlay et al., 1991) accommodate the shear motion. Here, we use microseismic data to analyze the fault geometry of two superimposed rift sections exposed in northern Iceland. Between the two rift sections, we identified a series of faults that are arranged along the main rift. These faults are left-lateral strike-slip. The movement between superimposed rift segments is right-handed. Together, these movements create a clockwise rotation of the fault, causing the crustal block to move in a book-like fault mechanism (similar to the arrangement of books placed diagonally on shelves) (Mandl, 1987). These faults may activate already existing crustal weakness, such as diagenetic intrusions, which originally traveled parallel to the main rift and had a 15 ° clockwise rotation. Pre-existing, the activation of weak surfaces parallel to the rift contrasts with the typical central ridge conversion fault, indicating that the unconverted fault accommodates shear misalignment between superimposed segments.