Study On Absorption And Attenuation And Inverse-Q Compensation Of Near Surface In Hangzhou Area

With the development of geophysical methods in every aspect,seismic prospecting is applied more and more to the survey of near surface geological structure in urban areas.These years one important issue faced by many scholars is how to increase signal to noise ratio and improve resolution effectively.Due to weathering,near surface layers usually exhibit the traits of low velocity and severe lateral velocity variation.Loose structure in near surface condition caused by weathering means low quality factor,and seismic waves will be absorbed intensively while travelling through these layers,causing limitation on effective information from received spectrum eventually.Therefore,the improvement of data quality is particularly important in seismic exploration.Methodology of seismic absorption is analyzed to find out the great effects of near surface posing on received signal.In order to achieve better results of subsequent method:inverse Q filtering,it is very important to carry out accurate formation quality factor inversion in the study area.After studying the physical definition and extraction methods of quality factor including time domain,frequency domain and other methods,especially a large number of quality factor inversion methods for up-hole data while studying the near surface,one method to invert quality factor using single borehole up-hole seismic and dual borehole up-hole seismic data is given.Based on the theory,the field data is processed to get formation quality factor which can contribute to understanding the regular pattern of absorption and attenuation of seismic waves in near surface.As an effective means to restore amplitude attenuation and correct phase distortion,inverse Q filtering is very commonly used in the processing of seismic data.The application of inverse Q filtering can improve the continuity of the seismic data events,thereby improving the resolution and signal-to-noise ratio of the profile.These days,inverse Q filtering is divided into three categories,using series expansion approximates inverse Q filtering,inverse Q filtering based on wave-field continuation,and other inverse Q filtering.Based on the near surface formation quality factor model,the post-stack seismic data is processed by inverse Q filtering based on wave field continuation,combined with the analysis of the static cone penetration data and core sampling data of the research work area,which verifies the practicability and effectiveness of this process.