Numerical modeling of nongeometrical effects by the Alekseev-Mikhailenko method

摘要: When the Alekseev-Mikhailenko method was used for exact numerical solution of Lamb's problem, a new strong nongeometrical arrival, denoted by S *, detected in synthetic seismograms computed P point source located proximity free surface. Strong dependence amplitude * arrival on depth is seen seismograms. It shown that under favorable circumstances, i.e., when less than one wavelength from surface, may be stronger ordinary body waves at same depth. This particularly important studies seismic wave fields oil exploration, where explosive sources are close to We show which features linear polarization and propagates with shear velocity, interpreted as result interaction between inhomogeneous plane integral representation source, Mathematically, corresponds saddle contribution along branch cut originating horizontal slowness p = α/β ( α, β indicate - -phase velocities, respectively). must considered approximation Weyl-Sommerfeld shallow used. Existence another effect, namely nonzero vertical component converted PS reflected surface normal incidence, also shown. In our opinion, this can easily explained higher order terms corresponding ray series. The prominence both effects suggests they should incorporated into any seismogram computations carried out sources.