4.6 Article

TTI equivalent medium parametrization method for the seismic waveform modelling of heterogeneous media with coarse grids

Journal

GEOPHYSICAL JOURNAL INTERNATIONAL
Volume 227, Issue 3, Pages 2016-2043

Publisher

OXFORD UNIV PRESS
DOI: 10.1093/gji/ggab310

Keywords

Numerical modelling; Computational seismology; Wave propagation

Funding

  1. National Key RAMP
  2. D Program of China [2018YFC1504204]
  3. Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) [GML2019ZD0203]
  4. Shenzhen Key Laboratory of Deep Offshore Oil and Gas Exploration Technology [ZDSYS20190902093007855]
  5. Shenzhen Science and Technology Program [KQTD20170810111725321]

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A new equivalent medium parametrization method has been developed to reduce the interface error of finite-difference methods in heterogeneous media on coarse grids. The method shows satisfactory results in simulating seismic waveforms and can be used in conjunction with higher-order and optimized schemes.
In recent years, many higher-order and optimized schemes have been developed to reduce the dispersion error with the use of large grid spacing in finite-difference seismic waveform simulations. However, there are two problems in the application of coarse grids for heterogeneous media: the generation of artefact diffraction from the stair-step representation of non-planar interfaces and the inaccuracy of the calculated waveforms due to the interface error. Several equivalent medium parametrization approaches have been proposed to reduce the interface error of the finite-difference method in heterogeneous media. However, these methods are specifically designed for the standard (2,4) staggered-grid scheme and may not be accurate enough for coarse grids when higher-order and optimized schemes arc used. In this paper, we develop a tilted transversely isotropic equivalent medium parametrization method to suppress the interface error and the artefact diffraction caused by the staircase approximation under the application of coarse grids. We use four models to demonstrate the effectiveness of the proposed method, and analyse the accuracy of each seismic phase related to the interface. The results show that our method can be used with higher-order and optimized schemes at 3 points per wavelength and produce satisfactory results.

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