Abstract We present a forward numerical modeling approach for fault-bend folding based on a velocity description of deformation. The approach incorporates algorithms capable of modeling multiple fault bends of different geometries (e. g. fault bends not stepping up from a detachment), imbricates, and variable velocity-boundary orientations, with corresponding varying slip ratios. When modeling contraction, the approach is capable of reproducing rounded-hinges and parallel folds with localized bed thinning or thickening commonly observed in natural structures. Extensional fault-bend folds can be modeled using the same set of equations, with the minor modification that velocity boundary orientations are defined independently of the fault shape. The modeled structures conserve area, and commonly observed features of extensional fault-bend folds, such as rollover structures with growth, are produced. Thus, we present a unified inclined-shear and flexural-slip general transformation associated with displacement over bends in faults, describing the theoretical framework which we have implemented in the associated program, fbfFor. We show the utility of this kinematic approach by matching seismic reflection examples, analog models, and mechanical models of fault-bend folds to create progressive, balanced kinematic interpretations and gain further insight into the formation of these structures.

中文翻译：

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断层弯曲折叠的正向运动学建模

摘要 我们提出了一种基于变形速度描述的断层弯曲折叠的正向数值建模方法。该方法结合了能够对不同几何形状的多个断层弯曲（例如，未从分离层向上延伸的断层弯曲）、叠瓦状和可变速度边界方向以及相应变化的滑移率进行建模的算法。在模拟收缩时，该方法能够再现圆形铰链和平行褶皱，并且在自然结构中通常观察到局部地层变薄或变厚。延伸断层弯曲褶皱可以使用相同的方程组建模，稍作修改，即速度边界方向独立于断层形状定义。模拟的结构保存了面积，以及通常观察到的伸展断层弯曲褶皱的特征，如翻车结构与增长，产生。因此，我们提出了与断层弯曲位移相关的统一斜剪和弯曲滑动一般变换，描述了我们在相关程序 fbfFor 中实施的理论框架。我们通过匹配地震反射示例、模拟模型和断层弯曲褶皱的力学模型来展示这种运动学方法的效用，以创建渐进的、平衡的运动学解释，并进一步了解这些结构的形成。