Characteristics and evolution of strike-slip faults in a stable cratonic block

The deformation pattern in the interior of cratonic blocks has critical implications for regional structural evolution but still remains an unresolved question. The southwestern Ordos Basin is at the convergence of multiple blocks, leading to intense and complex tectonic stress at this location. However, how the interior of the Ordos block responds to the complex stress field around it is still elusive. This study analyzes the characteristics and evolutionary history of faults in the southwestern part of the inner Ordos Basin using 3D seismic data. Three dominant sets of faults trending NW, NEE, and N–S have developed in the study area. All three sets of faults have subvertical dip angles and straight fault traces and structures that are common in such fault zones, such as flower structures and en-echelon and horsetail arrangements (all indicating strike-slip movement) are present. Structural deformation varies from the center to the periphery of the Ordos block. All three sets of fault systems exhibit small displacements. The polarity of the strike-slip changed in different periods, reflecting the transformation of the stress field in the southwestern Ordos Basin. This illustrates that the formation of cratonic faults is controlled by the regional stress field, while the related strain pattern in the interior of the cratonic block is very different from the deformation around its periphery. These characteristics also demonstrate the special nature of cratonic fault deformation.