# The Combined Compact Difference Scheme Applied to Shear-Wave Reverse-Time Migration  
[PERSON]  
1 State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing), Beijing 102249, China; [EMAIL_ADDRESS]  
2  
[PERSON]  
2 BGP Inc., China National Petroleum Corporation, Beijing 100088, China; [EMAIL_ADDRESS] (W.W.); [EMAIL_ADDRESS] (PS. ); [EMAIL_ADDRESS] (W.Y.) [PERSON]  
2  
[PERSON]  
2 BGP Inc., China National Petroleum Corporation, Beijing 100088, China; [EMAIL_ADDRESS] (W.W.); [EMAIL_ADDRESS] (PS. ); [EMAIL_ADDRESS] (W.Y.) [PERSON]  
1 State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing), Beijing 102249, China; [EMAIL_ADDRESS]  
2  
Footnote 1: [[https://www.mdpi.com/journal/applsci](https://www.mdpi.com/journal/applsci)]([https://www.mdpi.com/journal/applsci](https://www.mdpi.com/journal/applsci))  
Footnote 2: [[https://www.mdpi.com/](https://www.mdpi.com/)]([https://www.mdpi.com/](https://www.mdpi.com/))  
Footnote 3: [[https://www.mdpi.com/journals/pdf/10](https://www.mdpi.com/journals/pdf/10)]([https://www.mdpi.com/journals/pdf/10](https://www.mdpi.com/journals/pdf/10))  
and the accuracy of the scheme can reach that of the spectral method [16]. [PERSON] et al. (2000) used the combined compact difference scheme (CCD) for the convection-diffusion equation [17]. Since the mid-1990s, reverse-time migration has been applied to multicomponent wave seismic data excited from P-wave sources [18; 19; 20], having overcome calculation problems and interference artifacts in P- and S-wave simulations. During reverse-time migration, the P- and S-wave vectors of the source wavefield and the P- and S-wave vectors of the receiver wavefield are obtained and then imaged. In general, P- and S-wave wavefields are obtained either via the Helmholtz decomposition or by using the pled elastic-wave equation. These approaches are all designed for P-wave and elastic-wave sources, focusing mainly on how to retain the phase, amplitude, wavefield and vector characteristics of the wavefield efficiently during wavefield separation [21; 22; 23; 24; 25; 26; 27; 28]. In recent years, because of a breakthrough in S-wave vibrator technology, pure S-wave seismic data can be obtained via artificial excitation [29; 30]. As the wavelet length of an S-wave is shorter than that of a P-wave for the same frequency bandwidth, the resolution of its wavefield is higher, and its advantage for imaging beneath gas clouds area is unmatched by a P-wave [31]. Using the S-wave wavefield generated by an S-wave source for reverse-time migration imaging (RTM) is a key step for processing shear-wave data. Due to the characteristics of shear-wave wavelength, higher accuracy is required in numerical simulation. To ensure the accuracy of shear-wave RTM, a smaller time and spatial step than P-wave is needed, which reduces the calculation efficiency. To improve the accuracy and efficiency of shear-wave RTM, based on the characteristics of the shear-wave velocity model, we used the combined compact difference (CCD) and combined supercompact difference scheme (CSCD) for shear-wave (SH) RTM, with larger spatial grid conditions. [PERSON] (2002) applied the compact difference scheme to the numerical simulation of seismic wavefields [32]. Most recent studies of the finite difference scheme focus on the compressional wavefield from an explosion source, but few have studied the finite difference scheme based on the shear wavefield of the shear-wave source (SH-wave). This paper aims at the problem of low shear-wave velocity by introducing the supercompact difference scheme to suppress the numerical dispersion caused by the large spatial step.