The research project "Seismic waves in complex 3-D structures" (SW3D) started on October 1, 1993. The project celebrated its twenty-eighth anniversary last autumn. Its probably last twenty-eighth period finishes on April 30, 2022. More detailed information regarding the SW3D research project is available online at "http://sw3d.cz".
The Volume 31 of the serial Seismic Waves in Complex 3-D Structures of the annual reports of research project "Seismic waves in complex 3-D structures" summarizes the work done in the period December, 2020 - April, 2022. It also includes the DVD compact disk with updated and extended versions of computer programs, with brief descriptions of the programs, and with the copy of the SW3D research project WWW pages containing papers from previous volumes and articles from other journals.
Our group working within the project during the twenty-eighth year has consisted of five research workers: Vaclav Bucha, Petr Bulant, Vlastislav Cerveny, Ludek Klimes and Ivan Psencik. Ivan Psencik is the supervisor of PhD student Milosz Wcislo, with the PhD thesis on "Seismic waves in inhomogeneous, weakly dissipative, anisotropic media".
Veronique Farra (Universite Paris Cite, France) and Petr Jilek (BP, Houston, USA) visited us since the publication of the preceding Volume 30 in December, 2020.
The Volume 31 contains mostly the papers related to seismic anisotropy (3 of 4 papers). Two papers are devoted to attenuation. The Volume 31 may roughly be divided into five parts, see the Contents.
The first part, Velocity models and inversion techniques, is devoted to various kinds of inverse problems, to the theory developed for application to their solving, and to constructing velocity models suitable for ray tracing and for application of ray-based high-frequency asymptotic methods.
Paper "Kirchhoff prestack depth scalar migration of complete wave field using the prevailing-frequency approximation of the coupling ray theory" by V. Bucha represents a considerably revised and extended version of paper "Kirchhoff prestack depth scalar migration of complete wave fields in simple inhomogeneous weakly anisotropic velocity models: PP, PS1 and PS2 waves" of the Volume 29. The bugs in the data and computer code have been removed and all numerical examples have been recalculated. Moreover, 30% of the paper are brand new, featuring new figures and comparisons. The differences in migrated images due to different S-wave polarizations between the coupling ray theory and anisotropic ray theory, obscured in the previous paper, are now clearly visible. The paper simultaneously demonstrates feasibility of coupling-ray-theory migration in 3-D heterogeneous anisotropic structures on personal computers.
The second part, Waves in anisotropic elastic media, addresses the problems relevant to anisotropic elastic media.
V. Farra & I. Psencik, in their contribution "PS-wave moveout in anisotropic media of arbitrary symmetry and tilt", continue in generalizing approximate reflection moveout formulae (analytic approximation of travel times of reflected waves). As in the previous studies, their approach is based on the weak-anisotropy approximation. As the title indicates, this time they present and test the formulae of reflected converted PS waves in a homogeneous layer of arbitrary anisotropy. The tests show high accuracy even for the anisotropy strength around 20%.
The third part, Ray theory for isotropic viscoelastic media, is devoted to the extension of ray theory from isotropic elastic media to isotropic viscoelastic media.
In contribution "Comparison of ray and full-wave synthetic seismograms of reflected SH waves in attenuating media", I. Psencik, M. Wcislo & J. Carcione test the accuracy of the ray theory with the weak-attenuation concept, in which the attenuation is considered to be a perturbation of a reference elastic medium. They compare the ray-theory synthetic seismograms of an SH wave reflected from the interface between two homogeneous isotropic attenuating layers with the full-wave synthetic seismograms considered as an exact reference.
The fourth part, Ray theory for anisotropic viscoelastic media, is devoted to the extension of ray theory from anisotropic elastic media to anisotropic viscoelastic media.
In the previous Volume 30, L. Klimes demonstrated a problem with non-existing eigenvectors of the Christoffel matrix. However, the reference S-wave polarization vectors are used in our present code which should be generalized to anisotropic viscoelastic media. L. Klimes thus studies the properties of the S-wave polarization vectors in anisotropic viscoelastic media in paper "S-wave polarization vectors in anisotropic viscoelastic media".
The fifth and final part, DVD-ROM with SW3D software, data and papers, contains the DVD-R compact disk SW3D-CD-25.
Compact disk SW3D-CD-25, edited by V. Bucha & P. Bulant, contains the software developed within the SW3D research project, together with input data related to the papers published in the serial Seismic Waves in Complex 3-D Structures. A more detailed description can be found directly on the compact disk. Compact disk SW3D-CD-25 also contains over 560 complete papers from journals and previous volumes of the serial Seismic Waves in Complex 3-D Structures in PostScript, PDF, GIF or HTML, and 2 older books by V. Cerveny and his coauthors in PDF. Refer to the copy of the SW3D research project WWW pages on the compact disk. Compact disk SW3D-CD-25 is included in the Volume 31 in two versions, as the UNIX disk and DOS disk. The versions differ just by the form of ASCII files.
We are very grateful to our last sponsor, BP America Production Company, Subsurface Technology, Houston, TX, U.S.A., for the financial support which allowed us to prepare this last Volume 31 of the serial Seismic Waves in Complex 3-D Structures. We are also very grateful to all our former sponsors for supporting the SW3D research project and making the publication of the whole serial possible.
Prague, April 2022
Vlastislav Cerveny
Ludek Klimes
Ivan Psencik