Study On Propagating Characteristics Of Raylrigh Wave In Three-Dimension Complex Medium

With the low attenuation, high signal to noise ratio anti-interference ability, high resolution and the dispersion in layered media, Rayleigh wave has been widely used in the fields of seismic surveying and engineering test, its numerical simulation is also increasingly attention. In order to approach the realistic geological model and provide adequate theoretical support for the actual Rayleigh wave exploration, the propagation characteristics of Rayleigh surface wave in the three-dimensional complex media wear studyed with numerical simulation by staggered-grid finite difference method.Numerical simulation of three-dimensional wave equation requires a lot of computer memory and fast calculation speed. In order to overcome the limitation of large amount of data storage and slow compute speed, Parallel algorithm based on MPI (Message Passing Interface) was adopted to forward modeling Rayleigh wave using staggered-grid finite difference method. The model was divided into several sub-regions, all processors collaborate each other, parallel numerical simulate the sub-regions in each processor, accordingly, the purposes of accelerate the computing speed and expand the scale of the model was achieved.Acoustic-elastic boundary approach was adopted to implement the traction-free boundary and the exponential decay method was used to handle the absorbing boundary in the simulation process. Feasibility and correctness of the simulation were certificated by comparing the single-channel seismic records obtained by numerical simulation with the results of analytical solution and analyzing the snapshots. Rayleigh surface wave in the model of horizontal layered elastic medium, surface-breaking crack medium, underground cavity medium, terrain surface horizontal inclined medium, terrain surface doming medium and terrain surface downwarped medium were numerical simulated. In the case of rolling terrain surface, the scheme of coordinate mapping was adopted. Firstly terrain function and its derivative were lead into the wave equation and then solved using the staggered-grid finite difference method. In this paper, by the examples, the form principle of high mode of Rayleigh wave was analysed, the propagation of Rayleigh wave in the complex medium was vividly revealed, and its field characteristics was studyed.