Structural Deformation Characteristic Analysis With Superposition And Ratios Of Extensional And Strike-slip Stress:Insights From Physical Analog Experiments

Bohai Bay Basin has experienced multiphase tectonic movements during Mesozoic and Cenozoic.strike-slip and extensional stresses is two of the most main stress during basin developing and evolving,which worked together spatially and temporally to develop various tectonic deformation.Based on previous studies,this paper reduced mode of action of strikeslip and extension to two category,including different stages superposition and contemporary ratios.Then,according to Structure characteristics in file and oil data,this paper established geology model of the superposition and proportionality of strike-slip and extensional stresses,and design experiment model and update experimental instrument as well.The structural physical experiments were conducted under strike-slip stress and extensional stress,respectively,to verify rationality and validity of the experiments and confirm experiment parameters,such as material and displacement.Structural physical experiments under superposition and proportionality of strike-slip and extensional tectonic stresses were performed to understand the tectonic deformation,combined with seismic data interpretation.Results suggest that,in terms of extension prior to strike-slip,the tectonic deformation can be dominated by strike-slip that cut the early extensional deformation.Horizontally,it is characterized by en-echelon faults combination or strike-slip faults,while vertically,it exhibits flower-structure in shallow section and main faults cutting the early extensional fault in deep section.In terms of strike-slip prior to extension,it shows extensional faults at later stage accommodated by the reactive en-echelon R shears in horizon and flower liking tectonics in vertical.However,the proportion of strike-slip and extensional tectonic stresses has no influence on the tectonic deformation.Furthermore,the tectonic deformation can be classified into 3 types based on the relationship between the tectonic stress proportionality and faults as well as their combination.“Strike-slip stronger than extension” pattern is characterized by the mutual cut between “R”,“P” shear faults and extensional faults or “X”,“Y” fault combinations in the plane,and negative flower structure in vertical.“Extension and strike-slip equal” pattern is the “X”,“Y” fault combinations where en-echelon faults was cut by extensional faults in the plane.And convert slope and transform fault can be found,which cannot form main extensional-faults.Vertically,it composes of a series of normal faults with flower liking tectonic and Y structures of different scale.“Extension stronger than strike-slip” pattern is brush or comb structures in the plane and horsetail or flower-liking structures.