The capacity of any signal to carry information can be measured in a manner analogous to the volume of a container. Just as volume is the product of height times width times length, information capacity of seismic signals is related to a product of amplitude, frequency bandwidth, and length of the signal. (Fig. 5.1). This is more formally described in the readable book “Symbols, Signals and Noise” by Pierce. A dynamite energy source pulse produces an input signal having considerable amplitude, (height), and bandwidth, but very short length. A Vibroseis R energy source compensates for its limited amplitude by extending the input sweep signal over a relatively long length.
Reducing the bandwidth of a signal, as may be done with a band-pass filter, also reduces its capacity to carry information. A reduction in bandwidth not only limits the amount of information but also, to some degree, determines the type of information that can be carried. Yet, in the years prior to the advent of stacking and digital processing, application of a band-pass filter was practically the only procedure available to eliminate noise from seismic data.
Figures & Tables
“This publication originated in 1967 as a few notes to accompany a basic seminar for the Canadian SEG and was expanded in 1968 into an SEG Continuing Education course. Old and new information about geophysical data processing is consolidated in this edition. How to choose processes and parameters for any given field data is shown.”