Harmonic Attenuation Using Multiple Sweep Rates

Abstract

A technique includes generating seismic sweep sequences. Each of the seismic sweep sequences has an associated sweep rate. The technique includes varying the sweep rates to reduce harmonic distortion present in a composite seismic measurement produced in response to the sweep sequences.

What is claimed is: 
     
         1 . A system comprising:
 at least one actuator to generate seismic sweep sequences in a survey; and   a controller to control said at least one actuator to vary sweep rates of the sweep sequences.   
     
     
         2 . The system of  claim 1 , wherein said at least one actuator comprises a plurality of vibrators located at different vibrating points. 
     
     
         3 . The system of  claim 1 , wherein said at least one vibrator comprises a single vibrator. 
     
     
         4 . The system of  claim 1 , wherein the controller is adapted to control said at least one actuator to generate the seismic sweep sequences at a vibrator in a composite sweep sequence. 
     
     
         5 . The system of  claim 1 , wherein the controller is adapted to generate the sweep sequences sequentially at a vibrator and vary the lengths of the sweep sequences. 
     
     
         6 . The system of  claim 1 , wherein the controller is adapted to vary lengths of the sweep sequences to vary the sweep rates.