| The Changling Fault Depression and Lishu Fault Depression in the southern Songliao Basin are the areas where the important suture zone between the Northeast Block Group and the North China Plate passes.However,due to the surface sedimentary coverage,there is a lack of fine evidence of deep geophysical structure.The polarity and extension of the belt have not been clear.Finely describing the depth structure and determining the shallow-deep contact relationship between the Songnen block and the North China plate are of great scientific significance and economic value for understanding and understanding the Songliao Basin formation and evolution and the deep oil and gas resource occurrence spatial background.The purpose of time-depth conversion is to convert the time-domain depth profile into a depth-domain profile to obtain the true shape of the underground structure,and it plays an important role in the processing and interpretation of the reflection profile.In the field of traditional industrial exploration and development,mature time-depth conversion technology has been formed.The velocity field is mainly constructed by reflecting seismic data,and calibration and verification are carried out through well logging data,etc.,and a more accurate depth domain profile can be obtained.Its experimental depth concentration Less than 10 km.However,this deep seismic reflection profile detects that the target layer is about 30 km deep to the crust-mantle boundary.The travel time of the deep reflection wave is poorly sensitive to speed and lacks the constraints of logging data.It is difficult to obtain an accurate velocity structure.The deep velocity field is the focus and difficulty in this study.This study is based on the fine processing results of deep seismic reflection profiles obtained by the geological survey project,combined with the characteristics of the crustal scale vertical and horizontal velocity changes obtained by the previous deep seismic sounding in the Songliao Basin,through repeated adjustment of the velocity file combined with the characteristics of deep seismic reflection profile data,a more suitable velocity field model was selected to carry out the test of time-depth conversion velocity and the comparison of application effects.A set of high-precision time-depth conversion suitable for the crustal structure in the fault depression development area was preliminarily Technical processes and methods.Aiming at the structural characteristics of shallow and deep time domains in the southern fault depression area of the Songliao Basin,relevant methods of velocity mapping were explored,and the sensitivity of velocity changes in different depth domains from the surface to the Moho interface and upper mantle in deep seismic reflection profiles was studied degree.In the study,it was found that the mid-deep layer has weak energy and is susceptible to external interference.Therefore,the speed selection needs to be cautious.At the same time,because the profile crosses the rift zone underground,the speed will produce abrupt changes.In order to solve the above problems,this study adopted the method of speed spectrum point selection and manual interaction.The final conversion effect is good,and the imaging effect in the strong and weak areas is stabilized.The time domain to depth domain conversion results are true,and the depth information is accurate.The goal of deep structure homing.It is found that subduction remains in the deep part of the suture zone,and its subduction direction and extension state usually control the development of fault depressions in this area,and it is also the main interference area for seismic velocity field identification.Suggestions for deep conversion research work. |
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