I study the masters, never their students.— William Rowan Hamilton (1805-1865)
The distinction between intrinsic and apparent frequency-dependent seismic properties is nowhere greater than in the area of attenuation.
If we take a rock sample from a well core and test it in the laboratory at kilohertz to megahertz frequencies, we are likely to find some small amount of intrinsic attenuation, meaning the irrecoverable loss or conversion of wave energy into heat. That experiment will yield the frequency-dependent wave-energy loss as observed, for example, over the length of a 1-inch rock sample. In the frequency band of surface-seismic data, 5 to 100 Hz, the intrinsic attenuation is relatively constant and generally small. Extrapolating that level of intrinsic attenuation to a geologic section several kilometers thick still will predict only a modest loss of wave energy.
Figures & Tables
Elements of Seismic Dispersion: A Somewhat Practical Guide to Frequency-dependent Phenomena (SEG Distinguished Instructor Series No. 15) covers selected effects encountered in the acquisition, processing, and interpretation of reflectionseismic data. The material, based on the 2012 SEG Distinguished Instructor Short Course, shows how those phenomena arise, how they can be characterized, and the important information they contain. The text shows how spectral decomposition and time-frequency methods have led to improved understanding and use of nonlinear harmonics, near-surface guided waves, layer-induced anisotropy, velocity dispersion and attenuation, interference, and Biot reflection. Accessible discussion is augmented by examples, figures, and references to primary literature for further study. This book will interest technical managers and those who work in acquisition, processing, and interpretation of seismic data. (DISC on DVD, 761A, is also available.)