Numerical Simulation Study On Rupture Propagation Characteristics Along Buried Strike-Slip Fault

The tectonic earthquake induced by active fault,which has a wide scope of influence and causes the most serious geological disasters,often brings a large number of casualties and property losses,and covers more than 90% of the world's earthquake.The number of earthquake induced by positive(or negative)fault is large,but in recent years,the reports of the earthquake induced by the strike-slip faults increase year by year.The earthquake of IZMIT and Yushu are induced by underground hidden strike-slip faults.It is rarely reported to the study on surface rupture propagation characteristics along buried strike-slip fault.Therefore,the study on surface rupture propagation characteristics along buried strike-slip fault is fully realistic meaning.Aiming at the shortcomings of numerical simulation study in strike-slip fault,this article applies Weibull distribution randomly assigned and take mechanics parameters of overlying soil unit to achieve the characteristics of geotechnical inhomogeneous.Before rock damage,the stress and strain could be simplified to the phase of linear elasticity,and after damage,it went through linear strain-softening characteristics,then to ideal plastic state in the end.So,the softening modulus method is applied to achieve the elasticity modulus softening of the soil layer.The element of the bedrock and covering layer comply with mohr-coulomb yielding criteria.Embeded FISH language is applied Weibull distribution and softening modulus method to achieve secondary development of FLAC3 D.By comparing the numerical simulation results of strike-slip fault and previous similar simulation experiment results and earthquake scene investigation,we can draw the following conclusions:(1)With overlying surface rupture,the sand clay soil is the most severe,the clay is the second,the silt is the minimal when strike-slip fault came up.With different soil property,fracture spacing are various in the surface.For the surface dislocation of the soil layer,the silt is the largest,the clay is second,and the sand clay is the minimal.The surface sliding rate of the silt is greater than sand clay and clay.(2)The thickness of overlying soil and bedrock dislocation are very important parameters which will influence the characteristics of surface rupture expansion when in earthquake fault.With the thickness of overlying soil layer increasing,the surface spacing fracture decreases,and a certain critical thickness will prevent the fracture extension from spreading to the surface.The thickness of soil layer and surface dislocation are in inverse relation,but the thickness of soil layer has a little effect on the surface sliding rate.Bedrock dislocation is proportional to surface displacement difference and surface sliding rate,but the surface sliding rate shows abnormal rebound phenomenon.Along with the increase of the bedrock dislocation,surface discontinuous spacing fracture gradually evolved into a continuous broken zone.(3)The sliding rate of the surface is less than one of the bedrock,and the two rates are in direct proportion.Bedrock sliding rate does not affect the needed dislocation of the fracture extension to the surface,but it affects the form of surface fracture extension.When the bedrock fault rate equals to some value,the phenomenon of surface spacing fracture is most active.(4)By comparisons of numerical simulation results,similar model experiment and earthquake field results,we found the results consistent.