Viscoelastic representation of surface waves in patchy saturated poroelastic media  

作　　者：Yu Zhang Yixian Xu Jianghai Xia Ping Ping Shuangxi Zhang 

机构地区：[1]School of Geodesy and Geomatics, Wuhan University [2]Key Laboratory of Geospace Environment and Geodesy,Ministry of Education [3]Institute of Geophysics and Geomatics, China University of Geosciences [4]State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences [5]Subsurface Imaging and Sensing Laboratory, China University of Geosciences

出　　处：《Earthquake Science》2014年第4期421-431,共11页地震学报（英文版）

基　　金：support by the Natural Basic Research Program of China (the ‘‘973 Project’’,Grant No. 2013CB733303);the National Natural Science Foundation of China (Grant Nos. 41304077, 40974079);Postdoctoral Science Foundation of China (Grant No. 2013M531744);Key Laboratory of Geospace Environment and Geodesy (Grant Nos. 12-02-03)

摘　　要：Wave-induced flow is observed as the domi- nated factor for P wave propagation at seismic frequencies. This mechanism has a mesoscopic scale nature. The inhomogeneous unsaturated patches are regarded larger than the pore size, but smaller than the wavelength. Surface wave, e.g., Rayleigh wave, which propagates along the free surface, generated by the interfering of body waves is also affected by the mesoscopic loss mechanisms. Recent studies have reported that the effect of the wave-induced flow in wave propagation shows a relaxation behavior. Viscoelastic equivalent relaxation function associated with the wave mode can describe the kinetic nature of the attenuation. In this paper, the equivalent viscoelastic relaxation functions are extended to take into account the free surface for the Rayleigh surface wave propagation inpatchy saturated poroelastic media. Numerical results for the frequency-dependent velocity and attenuation and the time-dependent dynamical responses for the equivalent Rayleigh surface wave propagation along an interface between vacuum and patchy saturated porous media are reported in the low-frequency range （0.1-1,000 Hz）. The results show that the dispersion and attenuation and kinetic characteristics of the mesoscopic loss effect for the surface wave can be effectively represented in the equivalent vis- coelastic media. The simulation of surface wave propaga- tion within mesoscopic patches requires solving Blot＇s differential equations in very small grid spaces, involving the conversion of the fast P wave energy diffusion into the Blot slow wave. This procedure requires a very large amount of computer consumption. An efficient equivalent approach for this patchy saturated poroelastic media shows a more convenient way to solve the single phase visco- elastic differential equations.Wave-induced flow is observed as the domi- nated factor for P wave propagation at seismic frequencies. This mechanism has a mesoscopic scale nature. The inhomogeneous unsaturated patches are regarded larger than the pore size, but smaller than the wavelength. Surface wave, e.g., Rayleigh wave, which propagates along the free surface, generated by the interfering of body waves is also affected by the mesoscopic loss mechanisms. Recent studies have reported that the effect of the wave-induced flow in wave propagation shows a relaxation behavior. Viscoelastic equivalent relaxation function associated with the wave mode can describe the kinetic nature of the attenuation. In this paper, the equivalent viscoelastic relaxation functions are extended to take into account the free surface for the Rayleigh surface wave propagation inpatchy saturated poroelastic media. Numerical results for the frequency-dependent velocity and attenuation and the time-dependent dynamical responses for the equivalent Rayleigh surface wave propagation along an interface between vacuum and patchy saturated porous media are reported in the low-frequency range （0.1-1,000 Hz）. The results show that the dispersion and attenuation and kinetic characteristics of the mesoscopic loss effect for the surface wave can be effectively represented in the equivalent vis- coelastic media. The simulation of surface wave propaga- tion within mesoscopic patches requires solving Blot＇s differential equations in very small grid spaces, involving the conversion of the fast P wave energy diffusion into the Blot slow wave. This procedure requires a very large amount of computer consumption. An efficient equivalent approach for this patchy saturated poroelastic media shows a more convenient way to solve the single phase visco- elastic differential equations.

关 键 词：Surface wave Patchy saturation Viscoelastic equivalence APPROXIMATION 

分 类 号：P631.4[天文地球—地质矿产勘探]