Method of seismic wave amplitude normalization

DETAILED DESCRIPTION The present invention provides a method of processing seismic records involving the continuous monitoring of reflection wave amplitudes.
With the data from all the seismic detectors in the form of seismic disturbances as functions of time, two time windows are selected, one serving as a standard window, the other as a test window.
As employed herein, the term "window" is intended to define a time span over which a trace is to be examined or processed.
Since the time-dependence of the detected signals is related to the distances the signals must travel from the reflecting interfaces to the detectors, a plot, or trace, of a detected signal as a function of time is also a plot as a function of distance below the surface.
Therefore, the two windows represent two different subterranean levels.
The standard window is chosen in a part of the record containing reflections from continuous and consistent geologic formations, and the test window is placed at the depth to be explored.
For each trace, representing a different lateral position depending on the location of the corresponding detection system on the surface, the ratio of the summation of absolute amplitudes in the test window to the summation of absolute amplitudes in the standard window for that trace is calculated.
The trace-to-trace variation in weathered-layer wave attenuation is thus nullified by dividing each test window sum by a standard window sum which is determined largely by the amount of absorption experienced by the waves in that particular test window.
A comparision of the resulting ratios, from trace to trace, reveals lateral details of the subterranean geology at the test window depth without the distortion caused by the weathered layer.
In the particular embodiment disclosed, a complete mapping of the subterranean geology is obtained by making repeated ratio calculations for each trace as the test window traverses, or scans, the complete length of the trace in increments.
The ratio calculations for each trace are plotted as a function of time, and the plots for all the traces are aligned side-by-side according to the relative lateral positions of the corresponding detectors