High Resolution Processing Of Ultra Shallow Seismic Data For Active Fault Detection In Yanqing Basin

The Yanqing basin is a small Cenozoic faulted graben basin around 60km northwest of Beijing. Since the third century, the study area has been sinking strongly, forming a huge Quaternary sedimentary system. The neotectonic difference of the basin is strong,and there are many active faults. Active faults are closely related to earthquakes and geological disasters.Accurate positioning of ultra shallow layers of active faults plays an important role in saving land resources and earthquake resistance and disaster reduction in the capital circle. Shallow seismic exploration can effectively solve the hidden active faults near the surface of the city,and can accurately determine the location of the cutting stratigraphic horizon. By the thick Quaternary overburden, the influence factors of data acquisition and processing, ultra shallow seismic data processing has the following problems: (1) by gun source noise and random noise, ultra shallow seismic data near offset effective number is less; (2) the problem of anisotropic NMO formula based on hyperbolic time distance curve is not applicable, the loss of far offset data, resulting in ultra shallow coverage number is low; (3) due to the high frequency ultra shallow wave study area appeared in the end of more than 65Hz, clocked at 100-150Hz, in the deep wave above 100Hz do not have a sufficiently high signal-to-noise ratio, rely on the deep wave residual static correction can not accurately calculate the ultra shallow high frequency static correction problem; (4) ultra shallow CMP gathers less effective,will cause the speed of analysis is not accurate.This thesis aiming at the above problems,the main research contents as follows: (1) the application of LFAF denoising and RNA prestack random noise suppression method to realize separation of ultra shallow seismic data noise, improve the seismic trace number of near offset shallow layer; (2) non hyperbolic VTI medium based on dynamic time distance curve school method of far offset data effectively improve the leveling, ultra shallow seismic data coverage number; (3) the application of high precision coherent superposition method to solve the ultra shallow high frequency static correction for the difficult problem; (4) combined with multiple CMP gathers to form super gathers speed analysis. To improve the precision of velocity analysis of ultra shallow.Analysis and application of the subject in seismic data processing of high precision anisotropic velocity superposition, super gather velocity analysis method of ultra shallow seismic data, mainly to solve the following points: (1) through targeted ultra shallow signal noise separation and non hyperbolic time distance curve of VTI medium based on dynamic correction methods the 0-50ms coverage number increased from 2-4 times to 5-10 times; (2)velocity analysis application of super gathers to improve the quality of velocity spectrum, and improve the accuracy of velocity analysis; (3) high precision application of coherent superposition method, solve the high frequency static correction for the difficult problem of the stack the high frequency CMP gather effective wave events more straight to in-phase stack.In addition, the ultra shallow seismic data with high signal-to-noise ratio at the same time, the use of anti Q filter with pulse deconvolution and spectrum simulation, Pu Junheng deconvolution technology greatly enhanced the resolution, obtained 50ms with high signal-to-noise ratio and resolution of shallow seismic profile, provides the basis for interpretation for ultra shallow active fault location.