Method and system for acquiring marine seismic data using multiple seismic sources

A seismic surveying system, comprising:

• a first seismic energy source;
• a second seismic energy source;
• at least one seismic sensor array;
• a vessel adapted to tow the first source, to tow the at least one seismic sensor array, and to tow the at least one second source at a selected distance from the first source;
• and
• a controller adapted to actuate the first source and the second source in a plurality of firing sequences, the sequences having a time delay between firing the first source and the second source which varies between successive firing sequences, the times interval of firing the first and second source indexed so as to enable separate identification of seismic events originating from the first source and seismic events originating from the second source in detected seismic signals.

A method for determining signal components attributable to a first seismic energy source and to a second seismic energy source in signals recorded from seismic sensors, the first and second sources and the sensors towed along a survey line, the first source and the second source fired in a plurality of sequences, a time delay between firing the first source and the second source in each firing sequence being different than the time delay in other ones of the firing sequences, the method comprising:

• determining a first component of the recorded signals that is coherent from shot to shot and from trace to trace;
• time aligning die recorded signals with respect to a firing time of the second source in each firing sequence;
• and
• determining a second component of the signals that is coherent from shot to shot and from trace to trace in the time aligned signals.