Seismology of Azimuthally Anisotropic Media and Seismic Fracture Characterization

摘要: Traveltimes of reflected waves (reflection moveout) in heterogeneous anisotropic media are usually modeled by multioffset and multiazimuth ray tracing (e.g., Gajewski Psencĺk, 1987). Whereas ray-tracing codes sufficiently fast for forward modeling, their application moveout inversion requires repeated generation azimuthally-dependent traveltimes around many common-midpoint (CMP) locations, which makes the procedure extremely time-consuming. Also, purely numerical solutions do not give insight into influence anisotropy on reflection traveltimes. This chapter is devoted to analytic treatment conventional-spread media. For models with moderate structural complexity spreadlength-to-depth ratios close unity, CMP geometry welldescribed normal-moveout (NMO) velocity defined zero-spread limit (Tsvankin Thomsen, 1994; Tsvankin, 2005). Even presence nonhyperbolic moveout, NMO (Vnmo) still responsible most stable, conventionaloffset portion curve. The description Vnmo given here provides an basis inversion, helps evaluate contribution parameters traveltimes, leads a significant increase efficiency traveltime modeling/inversion methods.