Tomographic image of Rayleigh Surface Wave in Eurasia and western Pacific marginal seas

More than 1 800 seismic events(which occurred from 1982 to 2006,distributed in the range of 40°W~180°E,40°S -80°N,with magnitudes in 5.0~7.0 and focal depths shallower than 100 km)are selected from nearly 10,000 events recorded by 114 digital seismic stations in Asia,Europe and west Pacific networks.Totally 10450 accurate Rayleigh surface dispersion curves are employed for dispersion inversion,and the distribution map of Reyleigh wave group velocity in 28 periods from 8 S to 200 S for Eurasia continent and marginal seas of west Pacific are obtained.The great circle routes of surface waves cover Eurasia and the west Pacific Ocean.This paper preprocesses the original datum to determine surface dispersion curves at first, including the steps as following:intercepting Rayleigh surface wave,analyzing in time domain,to obtain the actual datum of dispersion.Then it lattice partitions the researched zone,and calculates the group velocity in theory,which means getting the datum of pure-path dispersion by inversion method of dispersion curve of latticing pure-path.At last,it inversed the pure-path dispersion to get the velocity distribution of S wave along with the depth of every unit by making use of datum for each unit as observed datum and by generalized inversion method like LSQR,SVD and so on.