Application Of Shallow Seismic Exploration Numerical Simulation In Longmenshan Foreland Fault Exploration

The development of seismic exploration technology and seismology is based on the study of seismic wave.The study of seismic wave is different from other geotechnical engineering studies.The physical test of seismic wave is difficult to realize in most cases,and it is even more difficult to realize the complex geological structure model in seismic exploration.Using computer technology can effectively simulate the propagation law of seismic wave in the underground complex structure,and has a great auxiliary role in the design of field data acquisition system,field single shot data recognition and post-processing,which has a great role in promoting the research of seismology and seismic exploration technology.First of all,based on the finite element numerical simulation theory and seismic wave propagation theory,this paper uses the finite element software to simulate the seismic wave field in the finite model by setting the viscoelastic boundary,and gets the full-time wave field snapshot and full-time wave field time record by forward modeling.Summarizing the experience of predecessors,the characteristics of shallow seismic exploration technology itself and the characteristics of the operation object,numerical simulation experiments determine the most suitable mesh division,which can achieve the minimum dispersion and maximize the calculation speed at the same time;According to the frequency of the artificial ramming source,the main frequency of the numerical simulation source is selected,and the source is chosen as the rake wavelet.Secondly,the different effects of geophone array of different observation systems and different offset on the original seismic data are studied,and smaller offset and trace spacing are selected as far as possible in the actual exploration.According to the forward modeling results of the observation system at different positions of the fault,the original seismic records at different positions of the fault show different characteristics.When it is above the fault,the reflection wave is disordered,and when it is outside the fault,the reflection wave is coaxial and continuous.Thirdly,by decomposing the fracture zone models with different dip angles and dividing the angles,it is found that decomposing the models in complex geological structures is more conducive to separating the wave fields in complex geological structures;Secondly,a variety of geological models are established for forward modeling.The shallow seismic reflection method is comprehensively simulated from simple model to complex structure.The propagation of seismic wave in complex geological structure is intuitively described by fulltime wave field snapshot and full-time wave field seismic record.Then,the forward technical conclusions are applied to the design of the observation system in the actual field exploration,and the seismic response characteristics of the forward results are more consistent with the actual exploration single shot data.Finally,in order to verify the accuracy of this study,a variety of geophysical methods are used to verify each other.In the same exploration area of shallow seismic exploration,highdensity electrical method and geological radar are used to realize comprehensive geophysical exploration.Finally,the results of these two kinds of geophysical exploration show the existence of faults,which proves the accuracy of field test data and the feasibility of numerical simulation in seismic exploration of complex faults.