Separation And Imaging Of Seismic Diffraction On Metal Deposit

Based on the Fresnel theory,if the geological body scale is less than a wavelength of seismic wave,the accuracy of seismic reflection imaging will drop drastically.But diffraction wave and scattered wave imaging from these small scale and heterogeneous geological bodies have a higher or much ultra-higher resolution.Diffractions can dectect and identify underground important structural information,such as fracture zone,faults,pinchout,reef boundary,small scale volcano rocks,intrusive,irregular salt domes,as well as other discontinuous geological body.This paper is based on the studies of the existing diffraction wave separation and imaging research methods,test the plane wave destruction filter(PWD)and the way of separation in the migrated dip-gathers with simple geological model,the Sigsbee2B model,the metal mine model and the kirchhofff time migrarion in the pre-/post stack domain and pre-stack depth migration.We have concluded some main points as following after applying the PWD filter on the seismic reflection data of Luzong deposit concentration area and Qinhang combination zone.1.Summarizing the progress of the research on the separation and imaging of seismic diffraction,and the concept,production condition,and its kinematics and dynamics characteristics of diffraction wave are defined.2.The synthetic model test showing that the separation technology of PWD filter in the post stack domain is more suitable for metal mine and deep reflection seismic data at present.The separation way in migrated dip-gathers is more intuitive,and the image quality is higher,so it can be used when the velocity model is enough accurate.3.The diffraction imaging applied in the metal mine is certisfied by synthetic data built on the real geological information combined with Xiaobaozhuang drilling data.The imaging of seismic diffraction has more clear and accurate than seismic reflection in the identification of complex and irregular ore bodies.4.The red basin in the Luzong deposit concentration not only has the structure of three layers,but also has the heterogeneity in sedimentary basin and is controlled by a series of listric faults along the fracture surface.Several groups of faults with NE tendency are found beneath Nihe deposit.Compared with Luohe deposit,these faults may provide the ore fluid channel for orebody,and closely related to mineralization.The more importanet is that there is another similar seismic characteristics as dome structure below the xiaobaozhuang ore bodies at the depth of 2500?3000m,which may be related to ore bodies.5.The separation and imaging method of diffractions is not only suitable for the use of metal mine seismic data with small receivier interval and high frequency,but also for the deep reflection seismic data with large receivier interval and low frequency.The results of deep reflection data in the Qinhang combination zone shows that the local geological structure information can be obtained by using the diffraction wave imaging in the shallow,middle and deep part.6.The depth of Moho in the North part of Qinhang metal logenic belt and its adjacent area is changed in the range of 31.5?34.5km between Yangtze plate and Cathaysian plate.The seismic geological characteristics of crust structure are obviously different.The crust in the Cathaysian plate has more obvious characteristics of seismic reflections than Yangtze plate,and the amplitude of reflections in Cathaysian plate are much weaker and smaller dip-angle,while the amplitude of reflections in Yangtze plate are much higher which the reflection has SE tendency in the upper crust and NE tendency in the middle and lower crust.