Patent ID: 7881160

Claim:
A method of operating a seismic vibrator array, comprising: simultaneously driving the vibrators in an array of multiple seismic vibrators each with a different one of a set of signals to transmit corresponding seismic signals, wherein the set of signals comprises a frequency-swept signal angle-modulated by a filtered maximal-length sequence code chip-shifted a different number of code chips for each vibrator and wherein the autocorrelation energy of any one of the signals and the cross correlation energy of any one of the signals and any other of the signals is spread non-uniformly over time from a first level at the start of a time interval when reflections of the corresponding seismic signals from a survey area are strong to a second level when reflections are weaker, wherein the first level is greater than the flat level of signals having uniformly spread cross correlation energy and the same time-bandwidth product as the set of signals, and wherein the second level is less than the flat level.