沉积层厚度对逆冲断层破裂扩展特征影响数值模拟

Numerical simulation on thrust fault's extension feature under sedimentary thickness' influence

为了深入揭示逆断层活动过程中沉积层的破裂扩展特征,采用数值模拟方法,研究断层倾角为45°时不同沉积层厚度对逆冲断层破裂特征的影响,得到以下主要结论:(1)随沉积层厚度的增加,断层活动对沉积层的作用力沿断层倾角方向从沉积层底部向上渐衰传递,接触点作用力最大,产生的变形随厚度增加在垂向上降低,并转化为横向传递,且横向影响范围逐渐增大。(2)逆冲断层破裂在两个临界沉积层厚度δ1,δ2的区分下存在三种扩展形式;沉积层厚度小于δ1时,基岩断层可扩展至沉积层表面并在表面形成破裂带;沉积层厚度大于δ2时,断层破裂只扩展到沉积层底部,其位移被沉积层内部的变形所吸收;沉积层厚度在δ1与δ2之间,基岩断层扩展到沉积层底部,并在表面形成张拉破裂带。研究结果表明:沉积层厚度是影响逆冲断层破裂扩展的重要因素之一,研究结果有助于进一步认识逆断层发震的地表变形特征。

For further revealing the feature of thrust fault＇s rupture and extension,using numerical simulating,the feature of the thrust fault＇s extension was researched at different sedimentary thickness when fault dip is 45°.The main conclusions are as follows：（1） Increasing with sedimentary thickness,the fault movement transmits from bottom to up part weakly along the fault-dip direction,the contact point＇s force is the largest.As thickness increasing,deformation reduces in vertical direction and translates into horizontal direction,even influence range in horizontal direction increases gradually.（2） Thrust fault＇s rupture and extension feature is divided into three forms by the critical thickness ？？,？？.When sedimentary thickness is less than ？？,bedrock fault extends to sedimentary surface and form rupture zone on surface;when sedimentary thickness is more than ？？,bedrock fault extends to sedimentary bottom,its displacement is absorbed by the sedimentary;when sedimentary thickness is between ？？ and ？？,bedrock fault extends to sedimentary bottom and form tension rupture zone on the surface.The numerical results imply that the sedimentary thickness plays important role in thrust fault＇s rupture and extension.The results obtained in this paper are valuable for further understanding the characteristics of surface deformation caused by thrust fault.