Estimation of near-surface attenuation using inversion of Rayleigh waves with fundamental and higher modes

Wave energy attenuation in near surface is an important physics issue for many applications. Various estimation methods have been developed for measuring Q from Rayleigh waves; however, the conventional methods are based on the assumption of layered earth model. In this paper we proposed a method to estimate near-surface Q from Rayleigh waves with fundamental and higher modes. This method can deal with complex media which are not layered. The simulated annealing algorithm is used and a new objective function is given. The velocities and densities of near-surface materials are assumed to be provided, Rayleigh waves are modeled by finite difference method; then based on the dispersion properties of Rayleigh waves, Rayleigh-wave mode separation is performed. The objective function is calculated using the amplitude information of fundamental and higher-mode Rayleigh waves. The numerical tests show that our method can obtain accurate Q in complex media.