Stability and Grid Dispersion of the P-SV 4th-Order Staggered-Grid Finite-Difference Schemes |
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Authors: | Moczo Peter Kristek Jozef Bystrický Erik |
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Institution: | (1) Geophysical Institute, Slovak Academy of Sciences, Bratislava, Slovak Republic;(2) Geophysical Institute, Slovak Academy of Sciences, Bratislava, Slovak Republic |
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Abstract: | Stability and grid dispersion in the P-SV 4th-order in space, 2nd-order in time, displacement-stress staggered-grid finite-difference scheme is investigated in the case of a homogeneous unbounded medium. All results, however, also apply to the velocity-stress and displacement- velocity-stress finite-difference schemes.
Independent stability conditions for the P and S waves are obtained by exact separation of equations for the two types of waves.
Since the S-wave group velocity can differ from the actual velocity as much as 5% for the sampling ratio 1/5, commonly used in numerical modelling, the sampling of the minimum S wavelength by 6 grid spacings (with the velocity difference not larger than 2.5%) is recommended.
Grid dispersion is strongest for a wave propagating in a direction of a coordinate axis and weakest for a wave propagating along a plane diagonal.
Grid dispersion in the 4
th
-order scheme for the sampling ratios s = 1/5 and s = 1/6 is smaller than grid dispersion in the 2
nd
-order scheme for s = 1/10 and s = 1/12, respectively. |
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Keywords: | finite-difference method staggered-grid schemes stability and grid dispersion |
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