Magnetic Mass-Lift Impulsive Seismic Energy Source Including Attracting and Repulsing Electromagnets

Abstract

A seismic energy source includes a base plate and a block fixedly coupled in a frame. The base plate is configured for contact with a part of the Earth's subsurface to be seismically energized. The frame has a first electromagnet associated therewith. A second electromagnet is disposed in a travelling reaction mass, which is movably disposed in the frame between the first electromagnet assembly and the top block. The reaction mass includes at least a third electromagnet associated therewith. The source has circuits for selectively energizing the first, second and at least a third electromagnets, and which are configured to energize the first and second electromagnets to repel each other such that the traveling reaction mass is lifted from the first electromagnet, and configured to energize the at least a third electromagnet after a selected delay time to cause attraction between the traveling reaction mass and the top block

1 .- 4 . (canceled) 
     
     
         5 . A method for seismic surveying, comprising: generating a magnetic repulsive force between a fixed component in a source frame and a traveling reaction mass in the source frame to cause the traveling reaction mass to move upwardly; generating a magnetic attractive force between the traveling reaction mass and a top block coupled to the source frame so as to cause the upward acceleration of the traveling reaction mass to impart a downward movement of the source frame; coupling energy from the downward movement into subsurface rock formations; and detecting seismic energy reflected from the subsurface. 
     
     
         6 . The method of  claim 5  wherein the generating the magnetic attractive force follows the generating the magnetic repulsive force after a time delay selected to limit an uppermost frequency in the energy from the strike. 
     
     
         7 . The method of  claim 5  wherein the generating magnetic attractive force follows the generating magnetic repulsive force after a selected time delay. 
     
     
         8 . The method of  claim 7  wherein the time delay is selected to limit an upper frequency of seismic energy caused by motion of the reaction mass.