AVO Response And Inversion Application Of Seabed Sediment Properties Parameters

The acquisition of physical properties related to seafloor sediments is of great significance for marine engineering construction and prevention of seafloor geological disasters.Different from traditional methods such as determination of sediment physical property parameters by acoustic in-situ measurement of geological seabed sampling,AVO technology can extract the seabed reflection coefficient from marine seismic data,and efficiently invert the seabed physical property parameters.Aiming at the sea-bottom interface,this paper mainly starts from the AVO response effect of the elastic and viscoelastic seabed interface,simulates the propagation and attenuation of seismic waves at the seabed interface,extracts the quality factor information,and the method of elastic inversion of seabed sediment parameters is discussed.After analyzing the previous scholars' elastic Zoeppritz approximate equation,the paper carried out two-step linear inversion of sediment elastic parameters and nonlinear constant step gradient algorithm inversion based on the approximate and accurate elastic equation.The nonlinear constant step gradient algorithm does not need to know the critical Angle,the iteration speed is fast,and the inversion result is more accurate than two-step linear inversion.After analyzing the influence of some factors on the inversion results,the field data from the south China sea are used for elastic inversion testing.Considering the existence of sediments such as sludge with strong attenuation on the sea floor,after analyzing different attenuation dispersion models,the seafloor interface is determined to be a constant Q model.Theoretically,the seismic wave propagation and attenuation of the seawater-seafloor interface are analyzed.Using the three interface conditions for the seafloor reflector,the tangential stress is 0,normal stress and normal displacement are continuous.The seafloor viscoelastic Zoeppritz equation is derived.Furthermore,the relationship among quality factor,P-wave velocity,attenuation vector,propagation vector,and attenuation angle is discussed.This paper used the ray tracing and finite-difference forward simulation method of different seafloor sediments through commercial software and programs to synthesize the viscoelastic seismic records and wavefield snapshot simulations of the seafloor interface,and compares the differences between viscoelastic and elastic seismic records,it is further proved that when the large quality factor is weak attenuation,the seabed sediment can be approximated as an elastic medium,but when the strong attenuation factor is small,the AVO curves under elastic and viscoelastic conditions are quite different,which proves the necessity of the simulation of viscoelastic.Finally,the equivalent quality factor of the model is calculated accurately by using the amplitude spectrum.