Method for separating seismic signals from two or more distinct sources

A method for seismic surveying, comprising:

• towing a first seismic energy source and at least one seismic sensor system;
• towing a second seismic energy source at a selected distance from the first seismic energy source;
• actuating the first seismic energy source and the second seismic energy source in a plurality of firing sequences, each of the firing sequences including firing of the first source and the second source and recording signals generated by the at least one seismic sensor system, a time interval between firing the first source and the second source varied between successive ones of the firing sequences;
• sorting the seismic signals such that events therein resulting from actuations of the first source are substantially coherent in all spatial directions;
• coherency filtering the first source coherency sorted signals;
• sorting the seismic signals such that events therein resulting from actuations of the second source are substantially coherent in all spatial directions;
• and
• coherency filtering the second source coherency sorted signals.

A program stored in a computer readable medium, the program including logic operable to cause a programmable computer to perform steps comprising:

• sorting seismic signals resulting from actuating at least two different seismic energy sources, the sources actuated to provide a variable time delay between successive actuations of a first one and a second one of the sources, the sorting performed such that events therein resulting from actuations of the first source are substantially coherent in all spatial directions;
• coherency filtering the first source coherency sorted signals;
• sorting the seismic signals such that events therein resulting from actuations of the second source are substantially coherent in all spatial directions;
• and
• coherency filtering the second source coherency sorted signals.