GPU를 이용한 이방성 탄성 거꿀 참반사 보정의 계산가속 = Acceleration of Anisotropic Elastic Reverse-time Migration with GPUs

국문 초록 (Abstract)

탄성 거꿀 참반사 보정(elastic reverse-time migration)을 통해 물리적으로 의미가 있는 영상을 얻기 위해서는 탄성 파동방정식(elastic wave equation)을 통해 재구성된 벡터 파동장(reconstructed vector wavefield)으로부터 P파와 S파를분리하는 파분리 알고리듬이 필요하다. 그리고 이방성을 고려한 탄성 거꿀 참반사 보정으로의 확장을 위해서는 이방성을고려한 탄성 모델링 알고리듬 뿐만 아니라 이방성을 고려한 파분리가 필요하다. 이방성 탄성매질에서의 파분리는 등방성탄성매질에서 주로 이용하는 Helmholtz decomposition과는 달리 탄성매질의 수직 속도 및 이방성 계수에 따라 계산된 유사미분필터(pseudo-derivative filter)를 이용한다. 이 필터는 적용에 많은 계산이 필요하기 때문에 이 연구를 통해 많은 양의 병렬계산을 효율적으로 수행할 수 있는 GPU (Graphic Processing Unit)를 이용하여 이방성 파분리를 수행하는 알고리듬을 개발하였다. 또한 GPU를 이용해 파분리를 수행하는 알고리듬을 포함하고 MPI (Message-Passing Interface)를 이용하는 효율성 높은 이방성 탄성 거꿀 참반사 보정 알고리듬을 개발하였다. 개발된 알고리듬의 검증을 위해 Marmousi-II 탄성모델을 기초로 수직 횡등방성(vertically transversely isotropy; VTI) 탄성모델을 구축하여 수치모형 실험을 수행해 다성분 합성탄성파탐사자료를 생성하였다. 이 합성탄성파 자료에 개발된 이방성 탄성 거꿀 참반사 보정 알고리듬을 적용하여 GPU와 MPI를 효과적으로 이용한 계산속도 향상과 이방성 파분리에 의한 영상결과의 정확도 향상을 보여주었다.

다국어 초록 (Multilingual Abstract)

To yield physically meaningful images through elastic reverse-time migration, the wavefield separation which extracts P- and S-waves from reconstructed vector wavefields by using elastic wave equation is prerequisite. For expanding the application of the elastic reverse-time migration to anisotropic media, not only the anisotropic modelling algorithm but also the anisotropic wavefield separation is essential. The anisotropic wavefield separation which uses pseudo-derivative filters determined according to vertical velocities and anisotropic parameters of elastic media differs from the Helmholtz decomposition which is conventionally used for the isotropic wavefield separation. Since applying these pseudo-derivative filter consumes high computational costs, we have developed the efficient anisotropic wavefield separation algorithm which has capability of parallel computing by using GPUs (Graphic Processing Units). In addition, the highly efficient anisotropic elastic reverse-time migration algorithm using MPI (Message-Passing Interface) and incorporating the developed anisotropic wavefield separation algorithm with GPUs has been developed. To verify the efficiency and the validity of the developed anisotropic elastic reverse-time migration algorithm, a VTI elastic model based on Marmousi-II was built. A synthetic multicomponent seismic data set was created using this VTI elastic model. The computational speed of migration was dramatically enhanced by using GPUs and MPI and the accuracy of image was also improved because of the adoption of the anisotropic wavefield separation.

참고문헌 (Reference)

1 Thomsen, L, "Weak elastic anisotropy" 51 : 1954-1966, 1986

2 Dellinger, J, "Wave-field separation in twodimensional anisotropic media" 55 : 914-919, 1990

3 Fomel, S, "Seismic wave extrapolation using lowrank symbol approximation" 61 : 526-536, 2013

4 Aki, K, "Quantitative seismology" University Science Books 2009

5 Sun, R, "Prestack scalar reverse-time depth migration of 3D elastic seismic data" 71 : S199-S207, 2006

6 von Alfthan, S, "Parallel programming with CUDA and MPI"

7 Hokstad, K, "Multicomponent Kirchhoff migration" 65 : 861-873, 2000

8 Martin, G. S, "Marmousi2: An elastic upgrade for Marmousi" 25 : 156-166, 2006

9 Yan, J, "Isotropic angle-domain elastic reverse-time migration" 73 : S229-S239, 2008

10 Yan, J, "Improving the efficiency of elastic wave-mode separation for heterogeneous tilted transverse isotropic media" 76 : T65-T78, 2011

11 Choi, H, "GPU를 이용한 이방성탄성매질에서의 파분리" 62-64, 2015

12 Ghorpade, J, "GPGPU Processing in CUDA Architecture" 3 : 105-120, 2012

13 Cheng, J, "Fast algorithms for elasticwave- mode separation and vector decomposition using lowrank approximation for anisotropic media" 83 : 991-997, 2013

14 Yan, J, "Elastic wave-mode separation for VTI media" 74 : WB19-WB32, 2009

15 Yan, J, "Elastic wave mode separation for tilted transverse isotropic media" 60 : 29-48, 2012

16 Han, B, "Elastic modelling in tilted transversely isotropic media with convolutional perfectly matched layer boundary conditions" 43 : 77-86, 2012

17 Jiao, K, "Elastic migration for improving salt and subsalt imaging and inversion" 82 : 2012

18 Lu, R, "Elastic RTM: anisotropic wave-mode separation and converted-wave polarization correction" 80 : 3171-3175, 2010

19 Stewart, R. R, "Converted-wave seismic exploration: Application" 68 : 40-57, 2003

20 Lu, R, "Comparison of elastic and acoustic reverse-time migration on the synthetic elastic Marmousi-II OBC dataset" 79 : 2799-2803, 2009