Study And Application Of Seismic Wave Characteristics Of Hammer Striking In Complex Strata

In the process of shallow seismic exploration,hammer excitation source is widely used because of its small negative impact on the environment,low cost and convenient operation.In the course of seismic exploration test,the seismic waves produced by different hammer sources not only affect the setting of seismic exploration and acquisition schemes,but also affect the resolution of seismic records and the processing of subsequent seismic data and the ease of interpretation.So,it is of great significance to study the seismic wave propagation characteristics excited by hammering source in the process of seismic exploration collection,processing and interpretation.This paper took the characteristics of seismic wave excited by hammer as the research object.We first studied the impact of source parameters(included the mass of hammer,the hammering velocity and the size of the base plate)on the seismic wave.We analyzed the variation characteristics of seismic wavelet excited by different source parameters through seismic exploration test combined with 3DEC numerical test,and try to find the influence of source parameters on amplitude and frequency of seismic wavelet.On this basis,using 3DEC analyzed the propagation characteristics of hammer seismic wave in a single structural surface stratigraphic model.We set two types of models: the structural surface of penetrating model and the structural surface of non-penetrating model.In these models,we study the influence of normal stiffness,tangential stiffness and structural surface inclination on the amplitude and frequency of hammering seismic wavelet.Through the above research,we draws the following working results:(1)When hammering on a viscous land table,the mass of the sledgehammer and the instantaneous velocity of hammering mainly affect the amplitude of seismic wave.With the increase of the mass of the sledgehammer or the instantaneous velocity of hammering,the amplitude of seismic wavelet increases and the increase is obvious.The specifications of hammering plate have no influence on the wavelet basically.(2)In the process of analyzing the random distribution of structural surface diameter in the stratum with known semi-trace length of outcrop surface,a new method to estimate the average diameter of structural surface based on the semi-trace line method was deduced.(3)Through the numerical simulation analysis of 3DEC,it is concluded that the normal stiffness and shear stiffness of the structure surface have certain high-frequency filtering effect on the hammering seismic wave,and the normal stiffness has greater effect on reflected wave,and the main frequency of reflected wave increases rapidly with the increase of the normal stiffness.The above results provide experimental basis for optimizing the setting of acquisition parameters in shallow seismic exploration and simplifying the processing and interpretation of seismic data,so that the shallow seismic exploration can be carried out more reasonably and efficiently under the excitation of hammer source.