(vel oss’ ∂t ē)
1. A vector quantity that indicates time rate of change of displacement.
2. In seismic usage (see Figure V-3) velocity refers to the propagation rate of a seismic wave without implying any direction, i.e., velocity is a property of the medium.
Adjectives preceding "velocity" are required to produce specific meaning and much confusion results because of the multitude of modifying adjectives in use (Figures V-3 and V-4). P- and S-wave velocities are given in Figure E-5 in terms of elastic constants for isotropic media and in Figure T-13 for polar anisotropy (transversely isotropic) cases.
Velocity is measured (or inferred) from sonic logs (q.v.), normal moveout (see velocity analysis), image focusing in depth-migration focusing analysis, well surveys (q.v.), and refraction time-distance curves (q.v.). For a discussion of the factors affecting seismic velocity, see Sheriff and Geldart (1995, 113–122).
3. Usually the apparent speed of a phase (phase velocity) is intended but sometimes the speed of the center of a packet of wave energy (group velocity). See group velocity, phase velocity.
- Hilterman, Fred J. (2001). Seismic Amplitude Interpretation. Society of Exploration Geophysicists. doi:10.1190/1.9781560801993.
- Whaley, J., 2017, Oil in the Heart of South America, https://www.geoexpro.com/articles/2017/10/oil-in-the-heart-of-south-america], accessed November 15, 2021.
- Wiens, F., 1995, Phanerozoic Tectonics and Sedimentation of The Chaco Basin, Paraguay. Its Hydrocarbon Potential: Geoconsultores, 2-27, accessed November 15, 2021; https://www.researchgate.net/publication/281348744_Phanerozoic_tectonics_and_sedimentation_in_the_Chaco_Basin_of_Paraguay_with_comments_on_hydrocarbon_potential
- Alfredo, Carlos, and Clebsch Kuhn. “The Geological Evolution of the Paraguayan Chaco.” TTU DSpace Home. Texas Tech University, August 1, 1991. https://ttu-ir.tdl.org/handle/2346/9214?show=full.