Study On Seismic Wave Excitation And Detection Based On Near-surface Investigation

Seismic acquisition is the first step in the field seismic exploration,whose data have an important effect on the seismic data processing.The acquisition consists of seismic wave excitation and detection.In terms of excitation,the theoretical research on the explosive excitation is relatively less and lack of systematic and thorough understanding over the years.It is not conducive to further optimizing the design of the excitation parameters.In terms of detection,the regular geophone arrays can suppress random noise and signal that leads to narrowing of seismic wave frequency band.Therefore,high density seismic acquisition technology has received more attention,among which the indoor array is an important part.So it is necessary to study the seismic acquisition technology systematically.Starting from the near-surface construction investigation,the characteristics of complex near-surface and the methods for obtaining near-surface parameters are expounded in this paper.Then I put our emphasis on the methods of explosive source excitation and the influence of excitation parameters such as charge weight,dynamite type,lithology,charge construction,explosive well depth and so on.Based on the explosion dynamics and numerical calculation,I focus on the explosive cavity and the pressure et al.Then further analysis is made on the change of energy transmitted to rock and soil based on the utilization ratio of explosive energy.On this foundation,I derive and obtain the quantitative relations of wavelets and analyze the factors affecting seismic wavelets.Based on the explosion dynamics and combined with research of explosive waves in air,water,soil and other materials,we take the energy utilization ratio as the criterion and analyze the influence of different coupling materials under decoupled charging.At the same time,I study the impact of porous media on the excitation.The achievement provides theoretical foundation to the closed technology in the seismic exploration.Finally,the effect on excitation of shooting depth,elongated source charge;delayed explosive source is analyzed based on the ghost theory.Correctness of the conclusion is validated through the forward modeling and gives some reasonable suggestions on explosive well depth.Finally,I put our emphasis on the combined detection method.By introducing beam-forming theory,the window weighting function based on the uniform-weighted(arithmetic mean weighted)is stuied.Considering the cost and the practicability of combined detection algorithm,I apply the algorithm to high density seismic acquisition technology and further research on the PCA-weighted and the MVDR-weighted combination.Based on the forward modeling and numerical calculation,the effect on signal-to-noise ratio and fidelity of different weighted combinations are investigated.The achievement extends our thought of the combined detection method.