The aim of the present work is to study the influence of preexisting pervasive strength anisotropy on the development of faults during two phases of extensions. Two different series of experiments are performed by deforming rectangular three-layered models either by orthogonal extension followed by oblique extension (series 1) or by oblique extension followed by orthogonal extension (series 2). The model represents a rectangular zone of rifting. The final fault architecture after two successive phases of extension is primarily controlled by the orientation of the pervasive strength anisotropy. The mode of far-field stress (orthogonal or oblique) plays a role in fault initiation during both the phases of extension. The growth of the faults which are orthogonal or oriented more obliquely ( β = 45°/60°) with respect to the rift normal is controlled by the direction of extension. However, the less oblique faults ( β = 15°) develop as strike-slip faults irrespective of the direction of extension. The phase 1 faults reactivate during the phase 2 extension only when they are parallel to the preexisting pervasive anisotropy. New faults parallel to the rift axis form only if the phase 2 extension is orthogonal (series 2). It is found to happen irrespective of the orientation of the strength anisotropy and of the 1st phase faults. Those faults act as linking faults for the highly oblique ( β = 45°/60°) phase 1 faults. New faults are formed following the anisotropy during both orthogonal and oblique phase 2 extension only if the anisotropy is oriented at low angle ( β = 15°) with the rift normal. The different fault patterns developed in the experiments can be matched well with natural examples reported from Karonga basin, Malawi rift, Kenya.

中文翻译：

---

在两个连续的伸展阶段期间预先存在的普遍各向异性区域内断层模式的演变：一项实验研究

目前工作的目的是研究预先存在的普遍强度各向异性对两个伸展阶段断层发展的影响。两个不同系列的实验是通过使矩形三层模型变形来进行的，即通过正交延伸然后倾斜延伸（系列 1）或通过倾斜延伸然后正交延伸（系列 2）。该模型代表了一个矩形的裂谷区。两个连续延伸阶段后的最终断层结构主要由普遍强度各向异性的方向控制。远场应力模式（正交或倾斜）在两个延伸阶段的断层起始中都起作用。相对于裂谷法线正交或取向更倾斜（β = 45°/60°）的断层的生长受伸展方向的控制。然而，无论延伸方向如何，倾斜度较小的断层（β = 15°）都会发展为走滑断层。仅当第一阶段断层与先前存在的普遍各向异性平行时，它们才会在第二阶段扩展期间重新激活。只有当阶段 2 延伸是正交的（系列 2）时，才会形成平行于裂谷轴的新断层。发现无论强度各向异性和第一相故障的方向如何，都会发生这种情况。这些断层作为高度倾斜 (β = 45°/60°) 1 相断层的连接断层。只有当各向异性以低角度（β = 15°）与裂谷法线定向时，才会在正交和倾斜相 2 扩展期间跟随各向异性形成新断层。实验中形成的不同断层模式可以与肯尼亚马拉维裂谷卡龙加盆地报道的自然实例很好地匹配。