Viscoelastic finite-difference modeling with application to shallow seismic refraction data

Koichi HAYASHI

OYO Corporation, Tsukuba Technical Research and Development Center,
43 Miyukigaoka, Tsukuba, Ibaraki, 305-0841 Japan. Tel.0298-51-6621 Fax.0298-51-5450
E-mail: hayashi-kouichi@oyonet.oyo.co.jp

Abstract

I have developed a two-dimensional, viscoelastic, finite-difference modeling method for complex surface topography and subsurface geological structure. Realistic modeling of seismic wave propagation in the near surface is complicated by many factors, such as strong heterogeneity, topographic relief and large attenuation. In order to account for these complications, we use a velocity-stress staggered grid and employ an O(2,4) accurate viscoelastic finite-difference scheme. The implementation includes an irregular free surface condition for topographic relief and a variable grid technique in the shallow parts of the model. Numerical tests indicate that approximately ten grid-points per shortest wavelength results in accurate calculations. The method is accurate and stable, and allows us to handle complex structure in finite-difference modeling. The algorithm is applied to 2-D modeling of the viscoelastic response of near surface structure beneath a 2-D refraction survey line. The P-velocity model was constructed by 2-D traveltime tomography, and S-velocity, density and Q were given empirically. Comparison of the observed waveform data with viscoelastic response clearly demonstrates the importance of inclusion of viscoelasticity. The character of the observed waveform data can be explained by velocities and Q distributions.

raeg99@tansa.kumst.kyoto-u.ac.jp

Last modified: Thu Nov 18 10:57:00 1999