Simulation and laboratory measurements of velocity and attenuation in viscoelastic body: A frequency dependent study with respect to viscosities.

摘要

Attenuation in the upper crust is a complex problem and a full understanding of intrinsic attenuation remains problematic, particularly in earth materials that are saturated with highly viscous liquids such as magma or bitumen. In literature, attenuation mechanisms have focused primarily on fluid displacements. Less emphasis has been placed on the potential absorption within the fluids themselves.;Frequency dependent simulations were performed to seismic attenuation and viscoelastic models with focus on the effects of both shear and bulk viscosities on the P and S wave velocities and attenuation.;Optimized ultrasonic techniques were employed to measure oil sand and sandstone samples. In particular, a specialized apparatus that allows length change monitoring on weakly consolidated samples is developed. Both longitudinal and shear wave speeds were measured and the pressure dependency of velocities is discussed in the end.;This work closes with conclusions from both the simulation and the laboratory as well as recommendations for future research. However, the study of properties and characteristics of highly viscous liquids saturated materials is an ongoing topic that requires continuous endeavors.;To gain insight into what might be expected in observation, first presented here are reviews of deformation behaviors, theories of elasticity, viscoelasticity and wave propagation, concepts and mechanisms of seismic attenuation/dispersion, laboratory techniques and previous measurements. Focus is put on the dynamic behaviors of waves in bulk viscosity incorporated viscoelastic models via relaxation theory.