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广义“断层转折褶皱”的几何学正演数值模拟

张逸昆, J.Suppe, 贾东, 卢华复   

  1. 南京大学 地球科学系, 南京 210093
  • 收稿日期:2005-12-20 修回日期:2005-12-20 出版日期:2005-12-20 发布日期:2005-12-20

Geometric Forward Modeling of Generalized “Fault-Bend Folding”

ZHANG Yi-kun, SUPPE John, JIA Dong, LU Hua-fu   

  1. Department of Earth Sciences, Nanjing University, Nanjing 210093, China
  • Received:2005-12-20 Revised:2005-12-20 Online:2005-12-20 Published:2005-12-20

摘要: 提出了一个广义“断层转折褶皱”的几何学数值模拟方法,并用C++语言编制了相应的数值模拟软件。该软件能模拟非常复杂的褶皱冲断系统,包括多转折“剪切断层转折褶皱”(multi-bend shear fault-bend folds)、复合楔体构造(composite wedge structures)、以及多滑脱层褶皱冲断系统(multi-detachment fold and thrust systems)。通过把一个沉积岩层分解成“膝折带”(kink-band)和“膝折楔”(kink-wedge)两部分,解决了模拟曲线形态的多转折断层转折褶皱的难点问题,而以往的几何学方法仅对真实的褶皱形态作了粗略的线性近似。通过把复杂的褶皱冲断系统分解成一系列迭加的滑脱层系,可以模拟复杂的楔体构造,并提供这些构造演化的二维动画。该软件被应用于美国加里福尼亚州的Wheeler山脊,一个活动的楔体构造,其构造解释得自于大量钻井数据,正演数值模拟再现了该构造的主要特征。

Abstract: We proposed in this paper a geometric method for the forward modeling of generalized fault-bend folding based on the kink folding theory and implemented the method with C + + , a widely used object-oriented computer language. The code has shown the ability to model very complicated fault-related folding structures, including multi-bend shear fault-bend folds, composite wedge structures and multi-detachment fold and thrust systems. By decomposing a sedimentary layer into kink-band and kink-wedge, we solved the difficulty in modeling multi-bend shear fault-bend folds of the curved shapes, while previous geometric methods only make the first order linear approximation of real folds with highly angular fold shapes. By decomposing fold and thrust systems into superposed detachment systems, it is possible to simulate extremely complex wedge structures and to do animation of the evolution of the structures. We applied this method to the Wheeler Ridge, California, an active wedge structure whose interpretation was constrained by well data according to Medwedeff (1992). Our modeling successfully reproduced the main features of this wedge structure.