Seismac wave3/23/2023 ![]() Except at large distances from the epicenter, the amplitudes of surface waves are much less than body waves. When the compression waves and shear waves are reflected by interaction with the ground surface, surface waves (Love waves and Rayleigh waves) are generated. Shear waves cause shear strains in the ground perpendicular to these radial lines. Compression waves cause compressive and tensile strains in the ground in a radial direction away from the hypo-center. Seismic wave propagation is a ground motion phenomenon that relates to the passage of body waves, including compression waves and shear waves, radially from the source of earthquake energy release (hypocenter) into the surrounding rock and soil medium. Wijewickreme, in Handbook of Seismic Risk Analysis and Management of Civil Infrastructure Systems, 2013 25.4.1 Wave propagation ![]() Seismic risk assessment for oil and gas pipelinesÄ.G. The additional data associated with anisotropic shear waves provide information about fracture orientation that is useful in reservoir characterization and can be used to provide more accurate images of the subsurface. Naturally fractured reservoirs can give rise to both a fast shear wave and a slow shear wave. The greater complexity is needed to mathematically model some systems found in nature, such as heterogeneous and fractured reservoirs. Relaxing the assumptions by, for example, attempting to model an anisotropic system requires more complex analysis. In practice, these assumptions often yield useful results. (5.3.1) is based on the assumptions that the medium is elastic, homogeneous, and isotropic. It was noted at the beginning of the preceding derivation that Eq. Other expressions for seismic velocities are presented later in this chapter. ![]() The S-wave is the shear wave, and the P-wave is the compressional wave. Irrotational displacement u I represents a longitudinal P (primary) wave, while the solenoidal displacement u S represents a slower transverse S (secondary) wave.
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