For this article, please refer to Report 7 of the consortium Seismic waves in complex 3-D structures, Dept. of Geophysics, Charles University, Prague, November 1998, pp. 349-374.

Here you can retreive the PDF version of camera ready copy (1.5 MB)


Stable finite-difference modelling of sedimentary basins

I. Oprsal, J. Zahradnik

Department of Geophysics, Faculty of Mathematics and Physics, Charles University,
V Holesovickach 2, 180 00 Praha, Czech Republic;

FD modelling of the two-dimensional   P-SV seismic  response is performed for the Volvi Lake sedimentary basin at EURO-SEISTEST site. The basin is 6 km long and 200 m deep. Viscoelastic linear rheology, with the attenuation described by Q proportional to frequency is used. The FD synthetics are accurate up to 4Hz. The site is characterized by complex structure, with  high velocity contrasts between individual blocks, (Vs=2600 m/s)/(Vs=425 m/s); also the Vp/Vs velocity ratio is up to 5. Numeric instabilities  have been found at  contacts between  blocks with  high and low Vp/Vs ratios. A simple trick  to stabilize the calculations for long FD runs (e.g. 20 000 time levels, or more) has been suggested. It consists  of a special algorithmic treatment of the material discontinuities, preventing mixing  of very large and very low values of the so-called effective material parameters within a grid cell. Discussed are also various possible ways of numerical evaluating the effective parameters in inhomogeneous media, some of which may yield incorrect results.  Appendix provides a comparison of the present FD  method  with an independent method for a  model with non-planar topography and several Vp/Vs ratios.


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