Strain accumulation and rotation in the Eastern California Shear Zone
Strain accumulation and rotation in the Eastern California Shear Zone
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DOI：
10.1029/2000jb000127
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发表时间：
2001-10
影响因子：
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通讯作者：
J. C. Savage;W. Gan;J. Svarc
中科院分区：
文献类型：
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作者：
J. C. Savage;W. Gan;J. Svarc
尽管东加利福尼亚剪切带（ECSZ）（走向为北偏西25°）与围绕太平洋 - 北美旋转极绘制的一个小圆并不完全重合，但三边测量和全球定位系统（GPS）测量表明，该区域内的运动对应于横跨一个垂直平面（走向为北偏西33°±5°）的右旋简单剪切，该垂直平面大致平行于当地小圆的切线（走向约为北偏西40°）。如果简单剪切是通过与剪切带大致平行的断层上的滑动而释放的，那么累积的旋转也会被释放，不会留下长期的旋转。在加洛克断层以南，主要断层（例如，卡利科 - 黑水断层）走向为北偏西40°，与最大右旋剪切累积所横跨的垂直平面的走向足够接近，以至于几乎完全能够通过右旋滑动来适应应变和旋转的累积。在加洛克断层以北，主要断层（走向约为北偏西20°）需要有倾滑以及走滑来适应简单剪切的累积。在这两种情况下，累积的旋转都会随着剪切应变一起释放。横穿东加利福尼亚剪切带的加洛克断层，没有被北北西走向的断层错断，而且尽管有长期左旋滑动的地质证据，但目前由于深部滑动，它似乎并没有在断层上累积左旋简单剪切应变。相反，其运动是由横跨正交的东加利福尼亚剪切带的右旋简单剪切来解释的。加洛克断层上的左旋滑动将会释放那里累积的剪切应变，但会增加累积的旋转，导致一个约80纳弧度/年（4.6°/百万年）的长期顺时针旋转速率。
Although the Eastern California Shear Zone (ECSZ) (strike -N25°W) does not quite coincide with a small circle drawn about the Pacific-North America pole of rotation, trilateration and GPS measurements demonstrate that the motion within the zone corresponds to right-lateral simple shear across a vertical plane (strike N33°W±5°) roughly parallel to the tangent to that local small circle (strike ∼N40°W). If the simple shear is released by slip on faults subparallel to the shear zone, the accumulated rotation is also released, leaving no secular rotation. South of the Garlock fault the principal faults (e.g., Calico-Blackwater fault) strike -N40°W, close enough to the strike of the vertical plane across which maximum right-lateral shear accumulates to almost wholly accommodate that accumulation of both strain and rotation by right-lateral slip. North of the Garlock fault dip slip as well as strike slip on the principal faults (strike ∼N20°W) is required to accommodate the simple shear accumulation. In both cases the accumulated rotation is released with the shear strain. The Garlock fault, which transects the ECSZ, is not offset by north-northwest striking faults nor, despite geological evidence for long-term left-lateral slip, does it appear at the present time to be accumulating left-lateral simple shear strain across the fault due to slip at depth. Rather the motion is explained by right-lateral simple shear across the orthogonal ECSZ. Left-lateral slip on the Garlock fault will release the shear strain accumulating there but would augment the accumulating rotation, resulting in a secular clockwise rotation rate ∼80 nrad yr -1 (4.6° Myr -1 ).