Method and system for generating shear waves and compression waves in the earth for seismic surveying

A seismic energy generating and transmitting system for transmitting into the earth compression waves and horizontally polarized shear waves comprising:

• a seismic energy generator having an upwardly-downwardly extending axis and generating a powerful explosive-like thrust directed in a downward direction along said axis whenever said generator is fired;
• a rigid ground plate positioned below said generator and having earth gripping means thereon adapted for contacting the earth's surface in gripping relationship;
• a pivot connection between said ground plate and said generator;
• the axis of said pivot connection being horizontal and being perpendicular to the axis of said generator for transmitting said powerful thrust downwardly from said generator through said pivot connection and thence through said ground plate into the earth;
• a transporter movable across the earth's surface having a load-bearing framework;
• lift means mounted on said framework for raising and for lowering said ground plate together with said pivot connection and said generator for placing said ground plate down onto the earth's surface with said gripping means in gripping relationship with the earth's surface and for raising said ground plate away from the earth's surface and
• tilt means for tilting said generator about said horizontal axis while said ground plate gripping means are engaging the earth's surface for orienting the generator axis vertically while said generator is fired for transmitting compression (P) waves into the earth and for inclining the generator axis away from vertical in a first direction while said generator is fired for transmitting into the earth first horizontally polarized shear (SH) waves together with compression (P) waves and for inclining the generator axis away from vertical in a second direction opposite to said first direction while said generator is fired for transmitting into the earth second horizontally polarized shear (SH) waves in an opposite shear direction from said first horizontally polarized shear waves together with compression (P) waves;
• said tilt means includes a lever member connected to said generator near said horizontal axis;
• a slidable coupling connecting an upper portion of said lever member to said lift means for permitting upward and downward movement of said lever member relative to said lift means while preventing said upper portion from moving in a horizontal direction relative to said lift means;
• said lever member includes a second portion projecting out of the plane defined by said generator axis and said horizontal axis;
• said tilt means also includes an elongated extendible and retractable linkage pivotally connected at one end to the outer end of said second portion of the lever member;
• and
• said extendible and retractable linkage is pivotally connected at its other end to an upper portion of said generator.

A discharge container for an air gun for generating waves in the earth, comprising:

• an elongate cylinder having a circular cylindrical wall with an upper end and a lower end;
• said upper end including means for attaching a cover plate;
• said lower end including means for attaching a cylinder head;
• said circular cylindrical wall having a lower thickened wall portion;
• and
• an annular manifold assembly extending circumferentially around said circular cylindrical wall at said thickened wall portion communicating with the cylinder;
• said lower thickened wall portion includes a plurality of circumferentially spaced holes spaced above the lower end of said cylinder for providing communication between the interior of the circular cylindrical wall and said annular manifold assembly;
• said means for attaching the cylinder head to said lower end of the elongate cylinder includes external flange means;
• said annular manifold assembly includes a cylindrical outer wall affixed at one end to said external flange means and extending upwardly therefrom in spaced relationship with said thickened wall portion of said circular cylindrical wall;
• an upper annular radial wall affixed to said cylindrical outer wall and said circular cylindrical wall to form an annular space;
• a lower annular radial wall affixed to said cylindrical outer wall and said circular cylindrical wall to divide the annular space and form a ring-shaped manifold chamber and lower passages with said lower annular radial wall defining the bottom of said ring-shaped manifold chamber and said upper annular radial wall forming the top of said ring-shaped manifold chamber;
• and
• said ring-shaped manifold chamber including means for coupling to a conduit.

A surface contacting plate for transmitting into the earth the shock waves from the sudden discharge of pressurized gas from an air gun, comprising:

• a disc-shaped plate member having a plurality of parallel projections depending therefrom to engage the surface of the earth in close coupling contact;
• coupling means affixed to said disc-shaped plate member and extending upwardly therefrom for mechanical coupling to a cylinder head of a discharge chamber for an air gun;
• transverse reinforcing means affixed to the upper surface of said disc-shaped plate member for adding strength to said disc-shaped plate member;
• said projections of said disc-shaped plate member include a plurality of spaced blades having narrow triangular cross-sectional earth penetrating configuration for biting into and gripping the earth for transferring horizontally polarized shear waves into the earth;
• a peripheral blade affixed to said disc-shaped plate which encircles said plurality of spaced blades;
• openings positioned between said uniformly spaced blades;
• a vacuum chamber formed in said disc-shaped plate;
• said openings providing communication between said vacuum chamber and the bottom of said disc-shaped plate;
• and
• vacuum coupling means formed in said vacuum chamber for receiving a suction line.

A surface contacting plate for transmitting into the earth the shock waves from the sudden discharge of pressurized gas from an air gun, comprising:

• a disc-shaped plate member having a plurality of projections depending therefrom to engage the surface of the earth in close coupling contact;
• coupling means affixed to said disc-shaped plate member and extending upwardly therefrom for mechanical coupling to a cylinder head of a discharge chamber for an air gun;
• transverse reinforcing means affixed to the upper surface of said disc-shaped plate member for adding strength to said disc-shaped plate member;
• said projections of said disc-shaped plate member include a plurality of spaced blades having a narrow triangular cross-sectional earth penetrating configuration for biting into and gripping the earth for transferring horizontally polarized shear waves into the earth;
• a resilient peripheral flange affixed to said disc-shaped plate member which encircles said projections to provide a vacuum seal when said disc-shaped plate member is placed in contact with the surface of the earth;
• openings positioned between said projections;
• a vacuum chamber formed in said disc-shaped plate;
• said openings providing communication between said vacuum chamber and the bottom of said disc-shaped plate;
• and
• vacuum coupling means formed in said vacuum chamber for receiving a suction line.

An air gun assembly incorporated into a cylinder head of a discharge container for generating waves in the earth, comprising:

• a cylindrical casing extending transversely through said cylinder head,
• said cylindrical casing having an intermediate region communicating with said discharge container;
• a substantially cylindrical three-chamber housing fitting into said cylindrical casing, said three-chamber housing including a first housing which defines a firing chamber, said first housing having a mating end, and a second housing which defines an operating chamber and a central chamber, said second housing having a mating end for mating with said mating end of said first housing;
• said firing chamber including a pressurized gas charging passage;
• said second housing including a plurality of discharge ports communicating with said central chamber;
• annular sealing means axially located within said second housing and abutting against said first housing at its mating end;
• means for holding said annular sealing means in position against said first housing at its mating end;
• shuttle means positioned within said central chamber, said shuttle means including a shank portion having an axial passage for supplying pressurized gas from said firing chamber to said operating chamber, an operating piston and a firing piston interconnected by said shank portion, said firing piston being seated against said annular sealing means and said operating piston closely abutting a partition which separates said operating chamber from said central chamber when said shuttle means is in it initial position;
• said operating chamber including a firing-trigger passage leading thereto adapted for causing a sudden discharge of pressurized gas through said discharge ports upon opening of said firing-trigger passage after said firing chamber and said operating chamber have been charged with pressurized gas;
• and
• said discharge ports being located in said intermediate region of said cylindrical casing for causing said sudden discharge to enter said discharge container.

Force transmitting apparatus for transmitting a sudden shock resulting from discharging an air gun in a container to a contact member closely coupled to the surface of the earth, comprising:

• a substantially vertical upright elongated cylindrical container for containing liquid, said substantially vertical upright elongated cylindrical container having a cylinder axis,
• said substantially vertical upright elongated cylindrical container having a rigidly closed lower end,
• an elongated air gun having a longitudinal axis, said elongated air gun being mounted in said rigidly closed lower end with said longitudinal axis of said air gun being perpendicular to said cylinder axis of said substantially vertical upright elongated cylindrical container,
• said air gun having at least one air discharge port communicating with liquid in said substantially vertical upright elongated cylindrical container,
• pivot coupling means attached to said rigidly closed lower end of said substantially vertical upright elongated cylindrical container,
• said pivot coupling means having an axis of rotation extending perpendicular to said cylinder axis of said substantially vertical upright elongated cylindrical container,
• a rigid ground contact member including multiple depending projections for engaging into the earth, and
• said rigid ground contact member being attached to said pivot coupling means for enabling said substantially vertical upright elongated cylindrical container to be inclined away from vertical for generating compressional waves and horizontally polarized shear waves in the earth upon discharging the air gun with said substantially vertical upright elongated cylindrical container inclined away from vertical.

A system for transmitting shear waves and compression waves into the earth for obtaining information about the geological features in the earth, comprising:

• a seismic energy discharge chamber closed by a head portion shaped to direct the discharge of pressurized gas upwardly from an air gun;
• a reaction mass positioned within said seismic energy discharge chamber for sliding upward movement therein in response to the sudden discharge of pressurized gas from the air gun;
• rigid pivot shaft means;
• coupling means fixedly coupled to said seismic energy discharge chamber and pivotally coupled to said rigid pivot shaft means;
• surface contacting plate means affixed to said rigid pivot shaft means so that said seismic energy discharge chamber may be pivoted about said rigid pivot shaft means relative to said surface contacting plate means to generate a downwardly inclined thrust relative to the surface of the earth which thrust has a vertical component for providing compression waves and a horizontal component for providing horizontally polarized shear waves;
• said seismic energy discharge chamber includes an incompressible liquid and said head portion is conically shaped to direct the thrust of the pressurized gas discharge upwardly toward said reaction mass;
• said surface contacting plate means includes depending projections for contact with the surface of the earth;
• and
• said rigid pivot shaft means and the air gun have their longitudinal axes located parallel to one another and in the same plane.

A cylinder head and air gun casing assembly for an air gun discharge container for generating waves in the earth comprising:

• a diverging generally concave wall having an apex portion and a base portion;
• mounting means on said base portion for attachment with a mating portion of a discharge container with the concave inner surface of said wall facing toward a discharge container mountable on said base portion;
• a cylindrical air gun casing having its cylindrical axis extending perpendicularly to and intersecting with the axis of said generally concave wall;
• said cylindrical air gun casing intersecting with said concave wall near said apex portion with the opposite ends of said cylindrical casing extending outwardly from the exterior of the generally concave wall, and
• said cylindrical air gun casing having at least one air gun discharge port therein located near the axis of said generally concave wall and aimed along the axis of said concave wall for directing the discharge from the port toward a discharge container mountable on said base portion.