2: Basic Principles
Definitions and Conventions
Polarization of Shear Waves
Before considering the more theoretical aspects of seismic wave propagation, we establish some basic definitions required to discuss characteristics of seismic P-waves and S-waves. As is demonstrated later, the physical entity (the divergence of the vector displacement) actually propagating as a seismic P-wave in an isotropic medium may be treated as a scalar quantity, while the physical entity involved in S-wave propagation (the curl of the displacement) is a vector quantity. Thus, seismic S-waves may inherently contain more information than P-waves. More importantly, when both P-wave and S-wave observations are taken together, we have a situation similar to using multiple simultaneous equations, and thus we can address multiple unknowns.
Figures & Tables
Many prospective basins of the world are, or will soon become, “mature” in the exploration sense. Increasingly we must resort to nonconventional technology and techniques to uncover the remaining hydrocarbon reserves that are often found in complex or subtle traps. Multicomponent seismology-the use of concurrent, combined shear (S)- and compressional (P)-wave seismology-is gaining acceptance in the exploration community as one tool that can provide direct measurements of subsurface rock properties. These measurements can detect new hydrocarbon accumulations, and aid in the efficient and economic development of newly found or existing reservoirs by providing detailed maps of reservoir porosity, lithology, and pore fluid distributions.