Onset of slip partitioning under oblique convergence within scaled physical experiments
Onset of slip partitioning under oblique convergence within scaled physical experiments
复制标题
缩放物理实验中倾斜收敛下滑移分配的开始
作者：
M. Cooke;K. Toeneboehn;Jennifer HAtch
倾斜会聚边缘存在滑移断层，同时存在活动的走滑断层和逆断层。这种系统违背了能量学上的考虑，即单个斜滑断层比多个断层更有效地适应变形。为了研究滑移分配的发展，我们记录了湿高岭土在低收敛（<30°）倾斜滑移基底位错的整个缩放实验中的变形。湿高岭土中预切垂直薄弱层的存在会影响断层的形态，但对于滑移分区来说并不是必需的。实验揭示了根据断层顺序和滑移分区程度划分的三种滑移分区发育类型。低收敛角实验（5°）在逆断层之前产生走滑断层。在中等收敛实验（10°–25°）中，逆断层先于走滑断层形成。走滑断层要么沿着现有的弱点（预切断层或先前的逆滑断层）发展，要么通过新的梯状裂缝的合并发展。沿着两个同时活动的倾斜断层的第三种局部滑动划分是暂时的，而全局滑动划分仍然存在。两个活动断层面的发育源于第一个断层发育后断层外应变模式的变化。对于早期走滑断层，断层外收缩积累起来，产生新的逆断层。具有早期叶状逆断层的系统适应有限的走滑并在上盘中产生延伸，从而促进走滑断层作用。在广泛的实验条件下对持续滑移分配的观察证明了为什么这种系统经常在世界各地的斜辐合地壳边缘中观察到。
Oblique convergent margins host slip-partitioned faults with simultaneously active strike-slip and reverse faults. Such systems defy energetic considerations that a single oblique-slip fault accommodates deformation more efficiently than multiple faults. To investigate the development of slip partitioning, we record deformation throughout scaled experiments of wet kaolin over a low-convergence (<30°), obliquely slipping basal dislocation. The presence of a precut vertical weakness in the wet kaolin impacts the morphology of faults but is not required for slip partitioning. The experiments reveal three styles of slip partitioning development delineated by the order of faulting and the extent of slip partitioning. Low-convergence angle experiments (5°) produce strike-slip faults prior to reverse faults. In moderate-convergence experiments (10°–25°), the reverse fault forms prior to the strike-slip fault. Strike-slip faults develop either along existing weaknesses (precut or previous reverse-slip faults) or through the coalescence of new echelon cracks. The third style of local slip partitioning along two simultaneously active dipping faults is transient while global slip partitioning persists. The development of two active fault surfaces arises from changes in off-fault strain pattern after development of the first fault. With early strike-slip faults, off-fault contraction accumulates to produce a new reverse fault. Systems with early lobate reverse faults accommodate limited strike-slip and produce extension in the hanging wall, thereby promoting strike-slip faulting. The observation of persistent slip partitioning under a wide range of experimental conditions demonstrates why such systems are frequently observed in oblique convergence crustal margins around the world.