关键词: 隐伏逆断层, 模拟实验, 投影条纹测试方法, 破裂扩展

Abstract: In this paper,the rupture propagation along reverse fault in bedrock towards the overlying sediment layer has been studied using modeling tests and the evolution of the vertical displacement field on the surface of sediment layer has been measured using fringe projection technique,in which the effects of fault displacement,thickness of sediment layer and fault dip have been analyzed.The research results indicate that fault in bedrocks propagates gradually towards the overlying sediment layer and a gradient zone of vertical displacement(i.e.a deformation zone)surrounding the projection line of the upper end of fault in bedrock is formed on the surface of sediment layer as the fault slips,given a constant thickness of sediment layer and a constant fault dip.The larger the fault displacement is,the larger the width of the deformation zone and the deformation intensity are.However,the width of deformation zone keeps constant and only the deformation becomes more concentrated as fault displacement increases after the fault propagates to the surface of sediment layer.Under the same fault displacement and the same fault dip,the thicker the sediment layer is,the wider the deformation zone controlled by the fault in bedrock is,i.e.the larger the influencing extent of the fault is.When the thickness of sediment layer exceeds a critical thickness,an extensional rupture may occur on the surface of the sediment layer caused by uplifting of the sediment layer.Under the same thickness of sediment layer and the same fault displacement,the width of the deformation zone on the surface of sediment layer decreases but the deformation intensity increases as fault dip increases.The experiment results imply that the critical fault displacement,the critical thickness of sediment layer and the fault dip play important roles in determining the surface deformation and rupture of earthquake generated by buried reverse fault.The results obtained in this paper are valuable for further understanding the characteristics of surface deformation caused by Wenchuan earthquake.

Key words: buried reverse fault, modeling test, fringe projection technique, rupture propagation