Orthorhombic fault patterns: The odd axis model and slip vector orientations
Orthorhombic fault patterns: The odd axis model and slip vector orientations
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DOI：
10.1029/tc008i003p00483
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发表时间：
1989-06
期刊：
影响因子：
4.2
通讯作者：
R. Krantz
中科院分区：
文献类型：
--
作者：
R. Krantz
共轭断层理论无法解释所有观察到的断层和滑移矢量模式。新的断层模型表明，正交断层模式代表了一般的三维应变情况，并将共轭断层归结为平面应变的特殊情况。奇轴模型将正交断层几何形状与主应变方向和比率联系起来。该模型还预测斜方断层的滑移矢量方向，表示为断层面上滑移矢量的倾斜度。假设一个主应变是垂直的，该模型预测在中等应变相对较小的应变场下发育的断层会出现陡峭或浅斜的倾斜滑移。仅当中间应变的相对大小较大时，斜倾斜滑动才可能发生。奇轴模型已在来自犹他州、内华达州、以色列和克里特岛的五组数据上进行了测试。在所有情况下，预测的滑移矢量方向都接近观察到的滑移。该模型还表明，当正交断层在三维应变场中重新激活时，滑移矢量可能与先前断层活动的滑移矢量相匹配，或者在方向上明显不同，从而产生具有双峰滑移模式的断层，如在盆地和山脉省的部分地区所见。最后的观察结果表明，三维应变可能在盆地和山脉的发育中发挥了重要作用。
Conjugate fault theory cannot explain all observed patterns of faults and slip vectors. New fault models suggest that orthorhombic fault patterns represent the general, three-dimensional strain case and relegate conjugate faulting to the special case of plane strain. The odd-axis model relates orthorhombic fault geometry to principal strain orientations and ratios. The model also predicts the orientations of slip vectors for orthorhombic faults, expressed as the rake of the slip vector on the fault plane. Assuming that one principal strain is vertical, the model predicts steeply or shallowly raking slip for faults developed under strain fields with relatively small magnitudes ofintermediate strain. Oblique-raking slip is possible only where the relative magnitude of the intermediate strain is large. The odd-axis model has been tested on five sets of data from Utah, Nevada, Israel and Crete. Predicted slip vector orientations lie close to the observed slip in all cases. The model also suggests that where orthorhombic faults are reactivated in a three-dimensional strain field, slip vectors may match those of the prior episode of faulting or be distinctly different in orientation, producing faults with bimodal slip patterns, as seen in parts of the Basin and Range province. This last observation suggests that three-dimensional strains may have played a significant role in Basin and Range development.