利用单剖面大地电磁三维反演识别沙德和玉农希断裂

文中基于实测的单剖面大地电磁数据,研究了沙德和玉农希断裂的深部电性结构,并从识别浅部活动断裂的角度出发,对比了二维模型及不同反演参数下单剖面三维反演模型对已有断裂构造深部结构的分辨能力。研究表明,单剖面数据的二维反演模型与三维模型均能获得合理可靠的区域深部结构特征。综合二维和三维解释模型,在现有的观测数据条件下,文中分析发现沙德断裂和玉农希断裂可能均切割上地壳高阻层,并向深部延伸到中地壳高导层。玉农希断裂在剖面位置近自立(或高角度倾向SE)从地表向深部延伸,沙德断裂的深部倾向为SE。此外,文中的实测资料结果表明,在现有计算能力条件下,三维单剖面反演模型也具有分辨局部断裂构造位置和深部几何结构的能力。最后,文中的工作反映了合适的水平网格间距和模型光滑参数对三维单剖面反演模型结果具有重要影响,过粗的水平网格尺寸和过大的模型水平光滑参数可能会导致三维单剖面反演模型无法正确分辨出浅部断裂构造。而在合理区间调整垂向网格的大小和数据误差门槛,可能对三维单剖面反演模型分辨浅部断裂构造的影响较小。带入倾子的三维单剖面反演能够进一步改善模型对出露地表的断裂构造深部几何结构的约束。

Using structure restoration maps to comprehensively identify potential faults and fractures in compressional structures

Faults and fractures of multiple scales are frequently induced and generated in compressional structural system. Comprehensive identification of these potential faults and fractures that cannot be distinguished directly from seismic profile of the complex structures is still an unanswered problem. Based on the compressional structural geometry and kinematics theories as well as the structural interpretation from seismic data, a set of techniques is established for the identification of potential faults and fractures in compressional structures. Firstly, three-dimensional(3D) patterns and characteristics of the faults directly interpreted from seismic profile were illustrated by 3D structural model. Then, the unfolding index maps, the principal structural curvature maps, and tectonic stress field maps were obtained from structural restoration. Moreover, potential faults and fractures in compressional structures were quantitatively identified relying on comprehensive analysis of these three maps. Successful identification of the potential faults and fractures in Mishrif limestone formation and in Asmari dolomite formation of Buzurgan anticline in Iraq demonstrates the applicability and reliability of these techniques.