Source acquisition with multiple frequency components

1. A seismic source array, comprising:

a first source including a first plurality of air guns having a first total volume, the first source having a first spectral output; and

a second source including a second plurality of air guns having a second total volume different from the first total volume, the second source having a second spectral output different than the first spectral output, wherein

the first source is configured to activate at a first interval, and

the second source is configured to activate at a second interval different than the first interval.

2. The seismic source array of claim 1 , wherein the second interval is approximately twice the first interval.

3. The seismic source array of claim 1 , wherein the first spectral output substantially does not overlap with the second spectral output.

4. The seismic source array of claim 2 , wherein an activation pattern of the first and second sources includes the first and second sources together followed by the second source without the first source.

5. The seismic source array of claim 1 , wherein the second source includes first and second sub-sources, the first and second sub-sources being configured to be towed spaced from and at opposing sides of the first source.

6. The seismic source array of claim 5 , wherein the first and second sub-sources of the second source are configured to activate substantially at the same time.

7. The seismic source array of claim 6 , wherein an activation pattern of the first and second sources includes the second source, followed by the first source without the second source, followed by the second source.

8. The seismic source array of claim 5 , wherein the first and second sub-sources of the second source are configured to activate with an alternating pattern.

9. The seismic source array of claim 5 , wherein an activation pattern of the first and second sources includes the first sub-source of the second source, followed by the first source, followed by the second sub-source of the second source.

10. A method of seismic surveying, comprising:

towing a first source having a first spectral output, the first source including a first plurality of air guns having a first total volume;

towing a second source having a second spectral output, the second spectral output being different than the first spectral output, the second source including a second plurality of air guns having a second total volume, the first total volume being greater than the second total volume;

activating the first source at a first interval; and

activating the second source at a second interval different than the first interval.

11. The method of claim 10 , wherein the first spectral output substantially does not overlap with the second spectral output.

12. The method of claim 10 , wherein an activation pattern of the first and second sources includes the first and second sources together followed by the second source without the first source.

13. The method of claim 10 , wherein the towing the second source includes towing first and second sub-sources spaced from and at opposing sides of the first source.

14. The method of claim 13 , wherein an activation pattern of the first and second sources includes the second source, followed by the first source without the second source, followed by the second source.

15. The method of claim 13 , wherein the activating the second source includes activating the first and second sub-sources with an alternating pattern.

16. The method of claim 13 , wherein an activation pattern of the first and second sources includes the first sub-source of the second source, followed by the first source, followed by the second sub-source of the second source.

17. The seismic source array of claim 1 , wherein the second interval is less than the first interval.