Shulu Sag Structural Features And Formation And Evolution Process Physical Simulation

Shulu sag,which is located in the southern part of Jizhong depression in Bohai Bay Basin,is a typical half-graben with fault in the east.There are no clear structural analysis results for Xinhe Fault-the boundary fault of Shulu Sag,and the genetic mechanism of the secondary normal fault zone and lateral anticline developed in the hanging wall of the fault.Via fine interpretation of 3D seismic data,the geometric,kinematic,and structural dynamic characteristics of Shulu Sag are studied systematically.On the basis of rollover structure models and predecessors' simulation results by sandbox analogue modeling,one experiment to reproduce the deformation in hanging wall of listric normal fault by 2D sandbox modeling,and three experiments with changing strike of listric normal fault by 3D sandbox modeling are designed and completed.By combining the results of experiments and structural analysis,the genetic mechanism of Shulu Sag is confirmed.Research suggest that:(1)Xinhe Fault is listric in cross-section,causing velocity and direction of movement,giving rise to bending of strata and activation of faults,thus the geometry of boundary fault controls the deformation in the hanging wall where faults develop densely,or in other words,the dense fault zone is controlled by the activation of boundary fault rather than regional nonuniform extension;(2)Xinhe Fault segments along strike,which can be divided into northern,middle and southern sections,corresponding to three dense fault zones – Nanxiaochen,Xicaogu,and Leijiazhuang Tectonic Zones;(3)the strike of dense fault zones coincide with that of boundary fault,whereas the oblique extension of boundary fault do not influence the strike of dense fault zones,but do influence that of the faults in these zones,that the strike of these faults rotates,showing a left step and flying geese model;(4)the linkage of Xinhe Fault segments lead to the change of fault throw along strike,that the main section of boundary fault shows a activation intense intensity much higher than that of the segment joints,it's the nonuniform extension that controls the formation of lateral accommodation zone,forming an NW transverse anticline and secondary normal faults,and the strike of these faults are nearly perpendicular to Xinhe Fault.