铲形断层:发展断层相关褶皱理论的“新引擎”

Listric Faults:A“New Engine”for Developing Fault-related Folding Theory

建立褶皱形态、断层结构和断层滑动之间的定量关系是当前地学研究国际前沿领域之一。Anderson断层理论和断层相关褶皱理论在该领域已经取得了瞩目的成果,二者都基于平面断层假设,但铲形断层及其上覆褶皱、地貌面弯曲变形在自然界中普遍存在,对上述理论形成了挑战。本研究利用前翼三角剪切和后翼简单剪切的综合模式,建立深部和地表耦合的铲形断层传播褶皱模型,用来解释上述构造变形机制问题。在此基础上,开展背斜区三维构造精细解析和铲形断层传播褶皱三维数值建模对比研究,实现构造变形从二维向真三维研究转换;准确限定孕震断层的铲形几何形态,为定量同震和震后变形提供直接的约束条件,为未来地震危险性评估提供科学数据支持;准确落实地下铲形断层和褶皱变形模型、裂缝发育区和构造型圈闭大小,服务于油气勘探开发。因此,铲形断层传播褶皱模型,一方面为完善和提升断层相关褶皱理论提供了新引擎,另一方面对区域构造变形分析、地貌演化重塑、地震危险性评价和油气资源前景评估有着重要的科学意义。

The quantitative relationships between fold morphology,fault structure,and fault slip are among the current frontier fields of geoscience research.Both Anderson fault theory and fault-related fold theory have made remarkable achievements in this field,but they are based on the assumption of planar faults.However,natural occurrences of listric faults,overlying folds,and deformations due to geomorphic surface bending pose challenges to these theories.In this study,we proposed a combined model of front wing trishear and rear wing simple shear and established a deep-and surface-coupling shovel fault propagation folding model that can explain these structural deformation mechanisms.Based on this model,we conducted detailed analyses of three-dimensional structures in anticlinal regions and comparative studies using three-dimensional numerical modeling of listric fault propagation folds to transform structural deformation research from two-dimensional to true three-dimensional analysis.We accurately defined the spade geometry of seismogenic faults and provided direct constraints for quantifying coseismic and post-seismic deformations,as well as scientific data,which are necessary for future seismic risk assessments.By accurately implementing underground listric faults,fold deformation models,fracture development areas,and tectonic trap sizes,our findings shed light on oil and gas exploration and development.Therefore,the proposed listric fault propagation folding model not only provides new insights for improving existing fault-related folding theories but also holds significant scientific significance for regional tectonic deformation analysis,geomorphic evolution reshaping studies,seismic risk assessments,and oil and gas resource prospect evaluations.