东营凹陷平南—石村变换构造发育特征及其定量表征

Development Characteristics and Quantification of Pingnan-Shicun Transfer Structures in Dongying Sag

同向超接型变换构造往往是由同向趋近型变换构造发育而来,当主干断裂的叠置部分较大时,其内部会受到与区域伸展方向一致的局部拉张作用,产生与主干断裂平行的纵向变换断层。根据区域伸展量守恒原理,结合同向超接型变换构造的发育特征及其主控因素分析,提出了"变换强度"(transfer degree)的计算公式来定量表征变换构造对主干断裂的调节程度,并将变换强度定义为变换构造的伸展量与主干断层最大水平位移量的比值;为了减小统计过程中的误差,采用了主干断层及其末端的水平位移为参数进行了变换强度的计算。该文选取了东营凹陷西部的平南—石村同向超接型变换构造为典型实例进行了分析,并运用平衡剖面技术验证了计算结果的准确性,二者吻合度好,表明该方法具有一定的可行性,为其他类型变换构造的定量表征提供了一定的思路。

Synthetic overlapping transfer structure usually evolves from the synthetic approaching structures when the master faults overlap relatively large areas and the overlapping areas will suffer from an extensional stress in the same direction as the whole regional one, producing lateral transfer faults （parallel to the master faults）. Based on the principle of regional elongation conservation and the analysis of development features and the controlling factors of synthetic overlapping transfer structures, ＂Transfer Degree＂ is proposed to quantify the degree to which a transfer structure can accommodate the extensional movement for the master fault. It is defined as the elongation ratio of transfer structure and master fault. In order to reduce errors, the horizontal displacement of a master fault and its end were used to calculate the transfer degree. As a case study, the Pingnan- shicun synthetic overlapping transfer structure was researched and its transfer degree was calculated. Finally, the calculation results were compared with those of the balanced cross sections. Both results matched very well, indicating that this method may be useful and could provide a way to quantify transfer structures.