Particle motion vector measurement in a towed, marine seismic cable

1. A particle motion sensor, comprising:

a sensing element capable of sensing a particle motion vector from a change in position thereof, and

a packing material in which the sensing element is positioned;

wherein the particle motion sensor is symmetric about its longitudinal axis and has a center of gravity coincident with its volumetric center.

2. The particle motion sensor of claim 1 , wherein the sensing element comprises a velocity meter or an accelerometer.

3. The particle motion sensor of claim 2 , wherein the accelerometer comprises a three-axis, micro electro-mechanical system accelerometer.

4. The particle motion sensor of claim 2 , wherein the sensing element comprises three single-axis, orthogonally oriented, micro electro-mechanical system accelerometers.

5. The particle motion sensor of claim 1 , wherein the packing material comprises:

a fluid;

a deformable, expanded foam body;

a polymer with added micro-spheres; or

a low density plastic.

6. An apparatus comprising:

a streamer;

a plurality of acoustic sensors distributed along the streamer; and

a plurality of particle motion sensors distributed along the streamer, at least one particle motion sensor being symmetric about its longitudinal axis and having a center of gravity coincident with its volumetric center.

7. The apparatus of claim 6 , wherein the particle motion sensor includes:

a sensing element electrically communicating with, but de-coupled from, the streamer and capable of sensing a particle motion vector from a change in position thereof; and

a packing material in which the sensing element is positioned.

8. The apparatus of claim 6 , wherein each of the particle motion sensors is co-located with one of the acoustic sensors.

9. The apparatus of claim 6 , wherein the acoustic sensors comprise a plurality of hydrophones.

10. The apparatus of claim 7 , wherein the sensing element comprises a velocity meter or an accelerometer.

11. The apparatus of claim 10 , wherein the accelerometer comprises a three-axis, micro electro-mechanical system accelerometer.

12. The apparatus of claim 10 , wherein the sensing element comprises three single-axis, orthogonally oriented, micro electro-mechanical system accelerometers.

13. The apparatus of claim 7 , wherein the packing material comprises:

a fluid;

a deformable, expanded foam body;

a polymer with added micro-spheres; or

a low density plastic.

14. The apparatus of claim 6 , further comprising an acoustic source.

15. A particle motion sensor, comprising:

an accelerometer capable of sensing a particle motion vector from a change in position thereof, and

a packing material in which the accelerometer is positioned;

wherein the particle motion sensor is symmetric about its longitudinal axis and has a center of gravity coincident with its volumetric center.

16. The particle motion sensor of claim 15 , wherein the accelerometer comprises one of three single-axis, orthogonally oriented, micro electro- mechanical system accelerometers.

17. The particle motion sensor of claim 15 , wherein the packing material comprises: a fluid;

a deformable, expanded foam body;

a polymer with added micro-spheres; or

a low density plastic.

18. An apparatus comprising:

a streamer;

a plurality of acoustic sensors distributed along the streamer; and

a plurality of particle motion sensors distributed along the streamer, at least one particle motion sensor being symmetric about its longitudinal axis, having a center of gravity coincident with its volumetric center, and including:

an accelerometer capable of sensing a particle motion vector from a change in position thereof; and

a packing material in which the sensing element is positioned.

19. The apparatus of claim 18 , wherein each of the particle motion sensors is co-located with one of the acoustic sensors.

20. The apparatus of claim 18 , wherein the acoustic sensors comprise a plurality of hydrophones.

21. The apparatus of claim 18 , wherein the accelerometer comprises a three-axis, micro electro-mechanical system accelerometer.

22. The apparatus of claim 18 , wherein the accelerometer comprises one of three single-axis, orthogonally oriented, micro electro-mechanical system accelerometers.

23. The apparatus of claim 18 , wherein the packing material comprises:

a fluid;

a deformable, expanded foam body;

a polymer with added micro-spheres; or

a low density plastic.

24. The apparatus of claim 18 , further comprising an acoustic source.

25. The particle motion sensor of claim 15 , wherein the accelerometer comprises a three-axis, micro electro-mechanical system accelerometer.

26. A particle motion sensor for use in a streamer, the particle motion sensor comprising:

a packing material; and

a micro electro-mechanical system accelerometer disposed within the packing material;

wherein the particle motion sensor is symmetric about its longitudinal axis and has a center of gravity coincident with its volumetric center.

27. The particle motion sensor of claim 26 , wherein the accelerometer comprises a three-axis, micro electro-mechanical system accelerometer.

28. The particle motion sensor of claim 26 , wherein the accelerometer comprises one of three single-axis, orthogonally oriented, micro electro-mechanical system accelerometers.

29. The particle motion sensor of claim 26 , wherein the packing material comprises:

a fluid;

a deformable, expanded foam body;

a polymer with added micro-spheres; or

a low density plastic.

30. The particle motion sensor of claim 26 , wherein the micro electro-mechanical system accelerometer comprises a monocrystalline semiconductor device.

31. The particle motion sensor of claim 26 , wherein the micro electro-mechanical system accelerometer comprises an inertial mass on the free end of a cantilevered beam.

32. A particle motion sensor for measuring seismic wavefield in water, comprising:

a sensing element capable of sensing a particle motion vector from a change in position thereof; and

a packing material in which the sensing element is positioned;

wherein the sensing element is a velocity meter or an accelerometer comprising a micro electro-mechanical system and the particle motion sensor is symmetric about its longitudinal axis and has a center of gravity coincident with its volumetric center.

33. The particle motion sensor of claim 32 , wherein the sensing element comprises a three-axis, micro electro-mechanical system accelerometer.

34. The particle motion sensor of claim 32 , wherein the sensing element comprises three single-axis, orthogonally oriented, micro electro-mechanical system accelerometers.

35. The particle motion sensor of claim 32 , wherein the packing material comprises:

a fluid;

a deformable, expanded foam body;

a polymer with added micro-spheres; or

a low density plastic.

36. A particle motion sensor, comprising:

a packing material;

a plurality of components including at least one sensing element, the components being disposed in the packing material in a manner defining an aperture through which a cable may extend;

wherein the sensing element is symmetric about its longitudinal axis and has a center of gravity coincident with its volumetric center.

37. The particle motion sensor of claim 36 , wherein the sensing element comprises a velocity meter or an accelerometer.

38. The particle motion sensor of claim 37 , wherein the accelerometer comprises a three-axis, micro electro-mechanical system accelerometer.

39. The particle motion sensor of claim 37 , wherein the sensing element comprises three single-axis, orthogonally oriented, micro electro-mechanical system accelerometers.

40. The particle motion sensor of claim 36 , wherein the packing material comprises: a fluid;

a deformable, expanded foam body;

a polymer with added micro-spheres; or

a low density plastic.

41. The particle motion sensor of claim 36 , wherein the cable comprises:

a power lead;

a command and control line; and

a date line.